Tremor is defined as an unintentional, rhythmic, oscillatory muscle contraction causing shaking movements of one or more parts of the body. It can affect the hands, head, face, jaw, lips, torso, and legs. Sometimes the voice may be affected as well.
Hand tremor is the most common form.
Tremor is a normal physiologic phenomenon. Most of us see our hands shaking slightly when we hold them out in front of us. Several factors, such as stress, anxiety, lack of sleep, smoking, and caffeine may exaggerate this tremor.
Although tremor is usually not a sign of a severe or life-threatening medical disorder, it can be both embarrassing and disabling to some people and make it harder to perform work and daily life tasks.
Tremor may occur at any age but is most common in middle-aged and older adults. It tends to affect men and women equally.
Tremors are classified as rest or action tremors.
Rest tremor occurs when the affected body part is completely supported against gravity. It may be an arm or a hand that is resting in the patient’s lap. Action tremors, on the other hand, are produced by voluntary muscle contraction. They may occur when writing or lifting a cup of coffee.
Postural tremor is a sub-type of action tremors and occurs when the person maintains a position against gravity such as holding the arms outstretched (1). Postural and action tremors, including exaggerated physiologic tremor and essential tremor, comprise the largest groups.
1. Exaggerated Physiologic Tremor
All normal persons exhibit physiologic tremor. However, it may often be invisible to the naked eye.
Physiological tremor is most evident in the outstretched hands but can be detected in the legs, head, trunk, jaw, and lips.
Enhanced physiologic tremor may be caused by medical conditions such as thyrotoxicosis (overactive thyroid gland), hypoglycemia (low blood sugar), the use of certain drugs, or withdrawal from alcohol, opioids or benzodiazepines. It is usually reversible once the cause is corrected (2).
Beta blockers, also known as beta-adrenergic blocking agents, are medications that may be used to reduce the amplitude of trembling during fine manual work (3). Beta blockers work by blocking the effects of the hormone epinephrine, also known as adrenaline. They are often used to treat high blood pressure (4), heart palpitations (5) and tremor due to an overactive thyroid gland.
2. Essential Tremor
Essential tremor is the most common neurologic disorder that causes postural or action tremor. It is also the most common movement disorder worldwide.
The prevalence increases markedly with age and ranges from 4.1 to 39.2 cases per 1,000 persons, to as high as 50.5 per 1,000 in persons older than 60 years (6). These figures may underestimate the actual prevalence, however, because up to 50 percent of persons with mild essential tremor are unaware of it (7).
More than half of patients with essential tremor have a family history of the disorder (8).
Essential tremor usually develops insidiously and progresses slowly. It often occurs first in the hands and forearms and may be more prominent on one side of the body and increases with goal-directed activity (e.g., drinking from a glass of water or writing).
Essential tremor may also affect the head, voice, jaw, lips, and face. It can include a”yes-yes” or “no-no” motion of the head.
The shaking usually increases with stress, fatigue, and certain medications such as central nervous stimulants. It may also increase with specific voluntary activities such as holding a spoon or a cup.
Interestingly, there is often a degree of voluntary control. Hence, the trembling may be suppressed by performing skilled manual tasks (9).
Although sometimes disabling, essential tremor is in itself a benign disorder and not life-threatening.
Rest, beta blockers, primidone (Mysoline), and alcohol ingestion decrease the trembling.
Primidone and propranolol are the cornerstones of maintenance medical therapy for essential tremor. These medications provide clinical benefit in approximately 50-70% of patients (10).
3. Parkinson’s Disease
Although Parkinson’s disease is probably 20 times less common than essential tremor, about one million Americans suffer from the disease (11).
Tremor is a common symptom of Parkinson’s disease and other Parkinsonian syndromes. However, it is not experienced by all patients with Parkinson’s disease.
The tremor includes shaking in one or both hands at rest. It may also affect the chin, lips, face, and legs. The shaking may initially appear in only one limb or on just one side of the body. It is often made worse by stress, strong emotions, and after exercise.
Sometimes, the trembling only affects the hand or fingers. This type of shaking is often seen in people with Parkinson’s disease and is called a “pill-rolling” tremor because the circular finger and hand movements resemble rolling of small objects or pills in the hand.
Although the trembling of Parkinson’s disease is usually defined as a resting tremor, more than 25 percent of people with Parkinson’s disease also have an associated action tremor (11).
The trembling of Parkinson’s disease differs from essential tremor in three fundamental ways (12):
Essential tremor is more likely to occur during voluntary activity of the hands whereas the trembling of Parkinson’s disease is more prominent at rest.
Parkinson’s disease is usually associated with stooped posture, slow movement, and shuffling gait.
Essential tremor mainly involves the hands, head, and voice. Parkinson’s disease tremors usually start in the hands and arms but also affect the legs, chin, and other parts of your body.
Although Parkinson’s disease can’t be cured, medications may markedly improve symptoms.
4. Intention Tremor (Cerebellar Tremor)
Intention tremor, also known as cerebellar tremor, presents as a unilateral or bilateral shaking, most often caused by stroke, brainstem tumor, or multiple sclerosis (2).
The neurological examination will reveal that finger-to-nose, finger-to-finger, and heel-to-shin testing result in increased shaking as the extremity approaches the target. Other signs include abnormalities of gait, speech, and ocular movements and inability to perform rapid alternating hand movements.
That the shaking typically increases in severity as the hand moves closer to its target, is in contrast to postural and action tremor (like essential tremor), which either remains constant throughout the range of motion or abruptly increase at terminal fixation (13).
Ataxia, a lack of voluntary coordination of muscle movements that includes gait abnormality, is typically associated with cerebellar tremor.
In cerebellar tremor, the finger-to-nose, finger-to-finger, and heel-to-shin testing result in worsening tremor as the extremity approaches the target.
5. Wilson Disease
Wilson disease is a rare autosomal recessive inherited disorder of copper metabolism that is characterized by excessive deposition of copper in the liver, brain, and other tissues (14). Wilson disease is often fatal if not recognized and treated when symptomatic.
Liver dysfunction is the presenting feature in more than half of patients.
The most common presenting neurologic feature is an asymmetric tremor, which is variable in character.
Wilson disease may also be associated with difficulty speaking, excessive salivation, ataxia, clumsiness with the hands, and personality changes.
6. Rubral Tremor
Rubral tremor, also known as Holmes tremor, is a rare symptomatic movement disorder, characterized by a combination of resting, postural, and action tremors.
It is usually caused by lesions involving the brainstem, thalamus, and cerebellum.
The disorder is often difficult to treat. Many medications have been used with varying degrees of success (15).
7. Primary Writing Tremor
Shaking that occurs exclusively while writing, and not during other voluntary motor activities, is referred to as primary writing tremor. Hence, it is a task-specific tremor that predominantly occurs and interferes with handwriting (16).
The cause and pathophysiology of this disorder are still unknown. It has been classified as a focal form of essential tremor and as a tremulous form of writer’s cramp (17).
Botulinum toxin injections and deep brain stimulation may be treatment choices for primary writing tremor (18).
8. Orthostatic Tremor
Orthostatic tremor is a rare disorder, characterized by a rapid trembling limited to the legs and trunk (19). It occurs exclusively while standing.
The disorder is often associated with extreme straining of both legs, fatigue, unsteadiness and a fear of falling. Standing upright for only a short period may be difficult.
The shaking may disappear partially or completely when an affected person is walking or sitting.
There is controversy within the medical literature regarding whether orthostatic tremor is a variant of essential tremor, an exaggerated physiological response to standing still or a distinct clinical entity (20).
The disorder may respond to treatment with clonazepam or gabapentin (Neurontin) (21).
9. Functional Tremor (Psychogenic Tremor)
Functional tremor, also known as psychogenic tremor, is a variable tremor that may decrease or disappear when not under direct observation.
Functional tremor is classified as a functional movement disorder, a term that is applied to disorders that manifest with physical symptoms, specifically abnormal movements (gait disorders, tremor, dystonia, etc.) but which cannot be attributed to any of known underlying organic disorders and which instead is presumed to be due to “psychological factors” (22).
Any body part may be involved, but, remarkably, the fingers are often spared with much of the trembling of the arm occurring at the wrist (13).
A characteristic that suggests functional rather than organic tremors is abrupt onset with immediate maximal severity, often precipitated by trivial emotional or physical trauma (23).
Patients with functional tremor often have more than one movement disorder, which can be a helpful clue to the diagnosis.
10. Drug-Induced Tremors
Several medications can cause or exacerbate tremor (2).
The shaking may affect the hands, arms, head, or eyelids. It rarely affects the lower body and may not always affect both sides of the body equally (24).
Drug-induced tremor will usually disappear when the medication causing the symptoms is stopped.
If the benefit of the medicine is greater than the problems caused by the tremor, lowering the dose may sometimes be helpful.
“Fatigue is here, in my body, in my legs and eyes. That is what gets you in the end. Faith is only a word, embroidered.” ― Margaret Atwood, The Handmaid’s Tale.
Fatigue or tiredness is a common medical complaint that may seriously affect people’s quality of life. However, despite many possible underlying causes, a specific medical disorder is seldom revealed. On the other hand, mood and anxiety disorders are commonly associated with fatigue.
Fatigue is regarded as a nonspecific symptom as it is not typically associated with a particular disease. It is one of the most common complaints reported to medical care providers.
Contrary to many other medical symptoms, fatigue is an entirely normal phenomenon in particular situations. We all become tired, but it usually gets better by rest or sleep. However, chronic fatigue as a medical symptom is typically persistent and not relieved by rest. The words lethargy and malaise are sometimes used to describe this condition.
Approximately 6-7 percent of the population experiences fatigue at any given time, and 24 percent of people will suffer from fatigue at some time during their course of life (1). Most studies show that fatigue is more prevalent in women than in men.
One study showed that 24 percent of primary care patients consider fatigue to be a significant problem (2). It is estimated that fatigue will result in approximately seven million office visits per year in the primary care setting in the United States (3). However, despite the frequency of medical utilization, one study found that only 10 percent of patients in an internal medicine clinic were found to have a medical cause for their fatigue (4).
Fatigue caused by an underlying medical condition such as a viral infection, anemia or hypothyroidism will usually clear up when the underlying condition is treated. That’s different from chronic fatigue which is persistent and is usually not be explained by a specific underlying medical condition. Fatigue that is present for more than six months is regarded as chronic.
An underlying medical or psychiatric condition can explain chronic fatigue in approximately two-thirds of the patients (5). The three major underlying psychiatric illnesses are depression, panic disorder, and somatization disorder (6).
Chronic fatigue syndrome (CFS), also known as systemic exertion intolerance disease (SEID) is regarded as a separate disease entity. Studies have indicated that approximately 15 percent of patients with chronic fatigue suffer from CFS (7).
Apart from affecting the quality of life, fatigue may negatively impact family life, social relationships, and performance at work. Consequently, it should be regarded as an essential public health issue. However, as so often with nonspecific symptoms that cannot easily be explained or fixed with a prescription or another simple measure, fatigue, as long as it is not caused by a severe medical disorder, often tends to be stashed away.
The Definition of Fatigue
Fatigue is a generalized perception of weakness or feeling worn out, drained or depleted.
Sometimes a distinction is made between physical and mental fatigue. However, in many cases, these occur together.
Physical fatigue is a reduced capacity to maintain physical activity or an inability to initiate physical tasks. However, mental fatigue is characterized by difficulties with concentration, memory, and emotional stability (8).
It is important to differentiate between daytime sleepiness and fatigue. Sleepiness is the inability to remain fully awake or alert during the day whereas fatigue is a subjective lack of physical or mental energy interfering with daily activities. Daytime sleepiness is a key feature of obstructive sleep apnea (9).
Fatigue should be distinguished from dyspnea and muscle weakness.
Dyspnea describes a sense of breathing discomfort or difficulty in breathing. It is often expressed as feeling out of breath or suffering from breathlessness (10). Muscle weakness implies lack of muscle strength and is associated with several neurological and skeletal muscle disorders. Of course, patients with dyspnea and muscle weakness may also complain of fatigue.
Chronic Fatigue
The duration of fatigue can be recent (less than one month), prolonged (more than one month), or chronic (over six months) (11).
Chronic fatigue syndrome (CFS), also termed myalgic encephalomyelitis (ME) is a disorder characterized by chronic fatigue. The disorder has no apparent cause.
CFS has also been named systemic exertion intolerance disease (SEID) to better reflect the condition’s hallmark which is post-exertional malaise. Post-exertional malaise describes a massive energy crash after a relatively minor exertion.
CSF is a heterogenous disorder. However, certain features are common to nearly all affected patients
Onset that may be sudden, often associated with a typical infection such as an upper respiratory infection or mononucleosis, or gradual over several months.
Overwhelming fatigue associated with additional symptoms (eg, altered sleep and cognition).
Symptoms characteristically exacerbated by excessive physical activity.
A pre-CFS medical history that is not one of multiple somatic problems (eg, chronic backache or chronic headache). Affected patients are typically highly functioning individuals who are “struck down” with this disease.
The cause of CFS is unknown, but it is believed to be an infectious disease with immunologic manifestations. There is often a history of an antecedent infection that precipitated the prolonged state of fatigue following the initial illness. Some have suggested that the infectious agent responsible for CFS is Chlamydia pneumoniae.
Recent evidence suggest that Covid-19 patients are at risk of developing CFS (13).
CSF is often accompanied by cognitive difficulties and orthostatic intolerance (14). Examples of cognitive problems include verbal dyslexia and difficulties with short-term memory.
It is estimated that between 836.000 and 2.5 million individuals are affected by CFS in the United States (15).
A recent study suggested that a blockage of a key metabolic enzyme could explain the profound lack of energy and other symptoms experienced by patients with CFS (166). The study suggests that patients with CFS have a reduction of amino acids that fuel oxidative metabolism, pointing to functional impairment of pyruvate dehydrogenase (PDH), a key enzyme for the conversion of carbohydrates to energy. Hence, the cells might switch to consumption of alternative fuels, causing a sudden shortage of energy in the muscles and a buildup of lactate, experienced by patients as a burning sensation in their muscles after minor exertion.
There is no specific diagnostic test for CFS. The diagnosis is based on clinical criteria, which are further supported by certain nonspecific tests. The absence of cognitive dysfunction should exclude CFS as a potential diagnosis.
In a 2015 report, the Institute of Medicine (IOM) wrote:
“However, CSF is poorly accepted and poorly understood, and the characteristics necessary to make the diagnosis are contested. Patients concern are often met with dismay and skepticism, if not outright dismissal. Clinicians, in turn, are confronted by competing definitions, which were usually developed for research and are quite complex and difficult to implement in busy clinical practice. Patients who are fortunate enough and persistent enough to receive a correct diagnosis frequently report long delays before their disorder was identified. It is almost certainly the case that the majority of affected patients are never diagnosed. This is unfortunate because effective symptom management is often available, whereas the wrong interventions can make symptoms worse (17).”
2. Idiopathic Chronic Fatigue
The first step in the evaluation of patients with chronic fatigue is to screen for an underlying medical or psychiatric illness. If no such disorders can be found and the patient does not fulfill the criteria for the chronic fatigue syndrome (CFS), he/she may be considered to have idiopathic chronic fatigue. The word ‘idiopathic’ reflects an unknown underlying cause.
Disability rates and need for healthcare is similar for patients with idiopathic chronic fatigue and CFS (18).
3. Fibromyalgia
Fibromyalgia is a chronic pain syndrome characterized by widespread nonarticular pain, stiffness, and fatigue.
Cognitive complaints, known as fibrofog, are present in 90 percent of patients (19).
For years, fibromyalgia has been regarded as a controversial condition. In most cases, no abnormalities are found on physical examination other than tenderness in certain areas affected. Laboratory and radiographic findings are normal. Thus, the role of organic illness has been questioned, and fibromyalgia has often been considered to be of psychogenic or psychosomatic origin (20).
Modern brain imaging has provided new insights into the mechanisms involved in fibromyalgia. Recent research suggests that fibromyalgia is a disorder of pain regulation, linking fibromyalgia to changes in brain activity (21).
Fatigue is a universal symptom of fibromyalgia. It is often most marked when arising from sleep in the morning. A typical quote is “No matter how much sleep I get, it feels like a truck ran me over in the morning (22).” Minor activities often seem to aggravate the fatigue.
Fatigue Caused by Underlying Medical Conditions
Fatigue may be caused by several underlying medical conditions. However, among patients with chronic fatigue, only a small proportion (approximately 10%) will have an underlying medical disorder as the primary cause of their symptoms.
Laboratory studies should include complete blood count, chemistry screen (electrolytes, glucose, renal and liver function test), thyroid stimulating hormone (TSH), and creatine kinase if muscle pain or weakness is present. Screening for occult hepatitis C viral infection may sometimes be appropriate as well as screening for HIV. These tests should reveal most common medical disorders potentially causing fatigue.
4. Anemia
Anemia is a medical condition in which the red blood cell count is below normal. Patients with anemia typically experience fatigue and loss of energy.
Iron deficiency anemia is the most common type of anemia worldwide. It is commonly caused by blood loss such as from heavy menstrual bleeding or bleedings from ulcers or tumors in the gastrointestinal tract.
Anemia may be caused by a deficiency of B-12 and folate.
Anemia may also be caused by diseases of the bone marrow such as leukemia and myelofibrosis
Many chronic diseases such as cancer, rheumatoid arthritis, and kidney disease may cause anemia.
5. Hypothyroidism
Hypothyroidism is a condition in which the thyroid gland doesn’t produce enough of the thyroid hormones known as T3 and T4.
Fatigue is one of the leading symptoms of hypothyroidism. Other symptoms include increased sensitivity to cold, constipation, dry skin, hoarseness, muscle weakness, muscle aches, thinning hair, depression and impaired memory.
The pituitary gland responds to diminished levels of T3 and T4 by increasing the secretion of thyroid stimulating hormone (TSH). Hypothyroidism is usually detected by elevated blood levels of TSH.
Treatment of hypothyroidism with synthetic thyroid hormone is usually simple, safe and effective.
6. Diabetes Mellitus
Many people with diabetes describe themselves as feeling tired, lethargic or fatigued at times.
Fatigue may be caused by an imbalance in blood sugar levels. It may be present when blood sugar is high and when it is low.
People with diabetes may also experience chronic fatigue that is not always related to their blood sugar levels. This phenomenon is known as diabetes fatigue.
7. Other Endocrine Disorders
Hypothyroidism and diabetes mellitus are examples of endocrine disorders known to cause fatigue.
Several other endocrine and metabolic disorders are associated with tiredness (23). Examples are hypogonadism (24), hyperparathyroidism with associated hypercalcemia, adrenal insufficiency (adrenal fatigue), apathetic hyperthyroidism, growth hormone deficiency, and glucocorticoid resistance (25).
8. Chronic Infections
Several chronic infections may cause fatigue. Examples are endocarditis (an infection of the heart valves), tuberculosis, mononucleosis, hepatitis, parasitic disease, HIV infection, and cytomegalovirus.
Additional laboratory tests may be necessary to reveal these disorders.
9. Autoimmune Disorders
Sometimes, in response to an unknown trigger, the immune system may begin producing antibodies that attack the body’s own tissues. This may lead to a chronic inflammatory response and is characteristic for most autoimmune disorders.
Examples of autoimmune disorders are rheumatoid arthritis, systemic lupus erythematosus (lupus, SLE), inflammatory bowel disease (IBD), multiple sclerosis (MS), type 1 diabetes mellitus, Guillan-Barre syndrome, psoriasis, Graves’ disease, Hashimoto’s thyroiditis, and myasthenia gravis.
Fatigue is a major component of autoimmune disorders. Tiredness described as “profound,” “debilitating,” and “preventing them from doing the simplest everyday tasks,” is a major issue for many patients, impacting nearly every aspect of their lives (26).
10. Cancer
Chronic fatigue is prevalent in people with cancer and can often be the most troubling symptom. This type of tiredness is sometimes called cancer-related fatigue or cancer fatigue.
Fatigue is now overshadowing pain and nausea/vomiting as one of the most feared symptoms of cancer and cancer treatment (27).
Cancer-related fatigue may be caused by the disease itself. Sometimes, tiredness is the first symptom of cancer. However, people with advanced cancer are more likely to have fatigue than people in the earlier stages.
Cancer-related fatigue may also be related to other factors such as anemia, anxiety, depression, and side effects of treatment.
11. Sleep Disorders
Daytime sleepiness is a key feature of obstructive sleep apnea (9).
However, sleepiness and fatigue are not the same. Sleepiness is the inability to remain fully awake or alert during the day while fatigue is a subjective lack of physical or mental energy interfering with daily activities.
Nonetheless, people with sleepiness due to obstructive sleep apnea use terms like fatigue, tiredness, and low energy to describe their symptoms.
12. Central Nervous System Disease
Several neurological conditions may be associated with fatigue. For example, tiredness is often a prominent symptom in patients with stroke, multiple sclerosis, and Parkinson’s disease.
It is important to look for symptoms or signs of central nervous system disease when evaluating patients with chronic fatigue.
13. Neuromuscular Disease
Fatigue may be present in several neuromuscular disorders such as Amyotrophic Lateral Sclerosis (ALS), Post-Polio Syndrome (PPS), Guillain-Barre Syndrome, Immune Neuropathy, Charcot-Marie-Tooth Disease, Myasthenia Gravis (MG), Metabolic Myopathy, Mitochondrial Myopathy, Muscular Dystrophy, Facioscapulohumeral Dystrophy, Myotonic Dystrophy (28).
Hence, it is important to look for muscle weakness and signs of neurological disease when evaluating patients complaining of tiredness.
14. Gastrointestinal Disorders
Several gastrointestinal disorders may be associated with fatigue. Examples are peptic ulcer disease, gastroenteritis, inflammatory bowel disease (IBD), cancer, and irritable bowel syndrome (29).
However, patients with gastrointestinal disorders will usually have other complaints as well, such as abdominal pain, nausea, vomiting, constipation, or diarrhea.
15. Cardiovascular Disorders
Tiredness may be a sign of underlying heart disease. Therefore it is important to look for symptoms such as chest pain (30) and shortness of breath (31).
The most common heart attack symptom in men and women is chest pain or discomfort. However, only half of women who have heart attacks have chest pain.Women are more likely than men to report back or neck pain, indigestion, heartburn, nausea, vomiting, extreme fatigue, or problems breathing (32).
Patients with chronic heart failure often have fatigue, diminished exercise tolerance, and fluid retention.
Heart failure occurs when the heart muscle is weakened and cannot pump enough blood to meet the body’s needs for blood and oxygen. In some cases, the pumping capacity of the heart muscle is preserved, but left ventricle is stiff with decreased compliance and impaired relaxation, which leads to increased fillingpressure in the left ventricle.
Heart failure is caused by an underlying heart disease that has caused damage to the heart muscle and/or an increased stiffness of the left ventricle. Coronary heart disease, hypertension, valvular disorders and dilated cardiomyopathy are the most common causes of heart failure.
Heart failure affects between 1–2% of the general United States population and occurs in 10% of those over 65 years old (33).
16. Chronic Obstructive Pulmonary Disease (COPD)
Chronic obstructive pulmonary disease (COPD) refers to a group of conditions that cause airflow blockage leading to shortness of breath, cough, mucus (sputum) production and wheezing. It includes emphysema, chronic bronchitis, and in some cases asthma.
Tobacco smoke is the leading cause of the development and progression of COPD in the United States (34). Genetic factors, exposure to air pollutants, and respiratory infections also play a role.
COPD was the third leading cause of death in the United States in 2014 (35).
Emphysema and chronic bronchitis are the two most common conditions that contribute to COPD.
Although shortness of breath is the most common symptom of COPD, many patients complain of fatigue (36).
Psychologic Causes of Fatigue
Psychiatric illness is present in 60-80 percent of patients with chronic fatigue (37,38).
17. Anxiety and Depression
Anxiety and depression are common causes of fatigue. The tiredness is usually persistent but may vary in intensity.
Up to three-quarters of patients with chronic fatigue also have mood or anxiety disorders. It has even been suggested that chronic fatigue is an atypical form (forme fruste) of anxiety or depressive states (39). In other words, chronic fatigue might be just another form of anxiety or depression.
Some people with depression experience total lack of energy sometimes called ‘anergia’.
There is evidence to suggest that depression may predispose individuals to subsequent fatigue (40). On the other hand, fatigue and depression have been found to predict and influence each other in time. Their association could partly be due to some common risk factors that give rise to both. For some, fatigue will come first; for others, depression will come first, but for most, it will probably be unclear (41).
18. Somatization Disorder
A person with somatization disorder is preoccupied with numerous “somatic” (physical) symptoms. The symptoms often cause significant distress and interfere with daily life. However, the person’s complaints cannot be explained by an underlying medical disorder.
Patients with somatization disorders often complain of pain or fatigue. Symptoms are often of gastrointestinal nature, such as nausea, bloating, and diarrhea. Erectile dysfunction is a common complaint in men. Women may experience menstrual irregularities. Neurological symptoms such as impaired coordination, difficulty swallowing, loss of touch or pain sensation, and double vision are often present.
It is important to understand that the patient is not faking. His/her complaints are real.
Somatization disorder usually begins before the age of 30 and is more common in women than men.
To qualify for the diagnosis of somatization disorder, somatic complaints must be severe enough to interfere significantly with a person’s ability to perform important activities, such as work, school or family, and social responsibilities, or lead the person experiencing the symptoms to seek medical treatment (42)
Patients with somatization disorder often undergo numerous medical tests before the psychological cause of their distress is identified.
Drug-Induced Fatigue
Fatigue is often associated with alcohol and drug addiction. It is also experienced by many individuals following withdrawal from these substances.
Many common pharmaceutical drugs have been linked to causing chronic fatigue.
19. Pharmaceutical Drugs
Fatigue is believed to be a common side effect of many conventional pharmaceutical drugs. These may be both over the counter drugs and prescription drugs.
Many drugs used for the treatment of high blood pressure are linked with fatigue. Cholesterol-lowering drugs like statins may also cause tiredness. Statin drugs are used by millions of people worldwide and are also known to cause muscle pain and muscle weakness in some individuals.
Antihistamines, commonly used to treat allergies, are known to cause fatigue.
Treatment with benzodiazepines, antidepressants, and antipsychotic drugs is also linked with tiredness. The same is true for opoid drugs which are commonly used for pain relief.
The Bottom-Line
Contrary to many other medical symptoms, fatigue is an entirely normal phenomenon in particular situations. We all become tired, but it usually gets better by rest or sleep. However, chronic fatigue as a medical symptom is typically persistent and not relieved by rest.
Chronic fatigue is a common and often disabling medical complaint.
An underlying medical disorder is found in approximately 10 percent of patients with chronic fatigue.
Up to three-quarters of patients with chronic fatigue also have mood or anxiety disorders.
If an underlying medical or psychiatric condition is not found, chronic fatigue syndrome (CFS) should be considered.
Patients who don’t have an underlying medical or psychiatric condition and don’t fulfill the criteria for CFS or fibromyalgia may be considered to have idiopathic chronic fatigue.
Treatment of fatigue will depend on the underlying cause.
General measures should focus on sleep, healthy diet, regular exercise, and stress reduction.
In-flight medical emergencies on commercial flights occur every day. In 2013, it was estimated that 44.000 such events occurred worldwide every year (1).
So if you are a doctor, a nurse, a medical student, an emergency medical technician or a person with first aid training, it is quite likely that one day your service will be needed in the skies.
The steadily increasing number of air travelers, the aging of the population, and the increasing number of air travelers with acute or chronic illnesses will undoubtedly increase the number of in-flight medical events in the future.
But, providing medical assistance in cramped quarters at 40.000 feet may not be an easy task. The low air pressure, the constant roar of the engine noise, and the presence of uninvited spectators will clearly not make the job easier.
However, understanding the essential nature of in-flight medical emergencies and some critical aspects of the aircraft environment will make us better prepared. Thereupon, this article is intended to answer important questions about in flight-medical emergencies and how they should be treated.
What are the most common causes of in-flight medical events? What is the proper way to respond? What medical resources are available on board the aircraft? Is expedited landing at the intended destination needed? When should a diversion to a closer location be recommended?
A Closer Look at the Statistics
There are about 5.000 aircraft in the sky at any given time, and the number of average daily scheduled passenger flights worldwide is approximately 26.500. In 2016, the number of scheduled passenger flights was 9.7 million (2).
More than 2.5 million domestic and international passengers fly every day. The estimated number of air travelers in 2016 was 3.6 billion. That’s about 800 million more than in 2011 (3).
In-flight medical events occur at a rate of 15 to 100 per million passengers with a death rate of 0.1 to 1 per million (4).
In 1998 – 1999, British Airways had 92 emergencies per million passengers (5). Of those, 70% were managed by cabin crew without the assistance of an onboard health professional.
It has been estimated that one in-flight medical emergency will occur in every 604 flights (4).
The Lufthansa Registry which contains data from the year 2000 onward documents a disproportionate increase in in-flight medical incidents in relation to passenger volume during the study period (6).
It has been estimated that a physician is present in approximately 40 percent of in-flight medical emergencies (7). However, these numbers have been shown to vary widely. The Lufthansa registry reports that in more than 80 percent of cases, a physician or other medical professional (e.g., nurse, emergency medical technician) gave help on board.
The Cabin Environment
Several medical issues may arise because of the general cabin environment and the nature of long-haul flights.
Turbulence may precipitate motion sickness and falling overhead items may cause injuries.
Long-distance flights may disturb circadian rhythm and disrupt the medication schedule of patients with chronic diseases.
The combination of inactivity and sitting with the legs down on the floor during air travel may cause blood to pool in the veins causing swollen feet and legs and even increase the risk of blood clotting (venous thromboembolism).
Cabin Pressure
The cruising altitude of commercial aircraft is usually maintained between 30.000 to 45.000 feet (9.100 to 13.700 m). The low atmospheric pressure at such heights is not compatible with survival. Therefore, aircraft cabins are pressurized during flight to the equivalent of 5.000 to 8.000 feet (1.500 – 2.400 m) above sea level.
Due to the lowered cabin pressure, the partial pressure of oxygen in cabin air at cruising altitude is 25-30% lower than at sea level. Although relatively well tolerated by most people, this may be problematic for some patients with hypoxia due to underlying heart-and lung conditions.
Because of the decreased cabin pressure, gases within body cavities will usually expand. The expansion of trapped gas may cause an earache because of swelling air in the middle ear, facial pain due to air in the paranasal sinuses, and abdominal pain due to distention of air in the intestine.
Cabin Air Quality
A part of the cabin air (no more than 40-50%) is recirculated and cleaned with special filters (HEPA), while the remainder is derived from the outside air (bleed air). The humidity on board ranges from 6-18% depending on the compartment (6). Optimal humidity varies between 40-70%. Hence, cabin air is arid.
The low humidity of cabin air can cause dry skin, dry eyes, and airways, sometimes triggering respiratory problems, especially in patients with asthma or chronic lung disease.
Insensible water loss in the dry cabin environment, combined with a low fluid intake on long flights, may cause dehydration although this is unlikely to cause symptoms in healthy individuals.
The air conditioning and ventilation system in a commercial aircraft can maintain low counts of microorganisms in the cabin. However, there are reports of individuals contracting a number of infectious diseases through airborne transmission (8, 9).
Airline Protocols For Managing In-Flight Medical Events
In the aircraft setting, the pilot, assisted by the co-pilot has overall responsibility for the passengers, the crew, the flight and the aircraft (10).
The cabin crew is responsible for managing in-flight medical emergencies. They are trained to recognize common medical problems and provide first aid and basic cardiopulmonary resuscitation.
The cabin crew should make the initial assessment of the ill passenger and is responsible for informing the captain about the situation.
The crew may then request assistance from onboard medical professionals as needed. Furthermore, the captain may decide to call ground-based medical support (GBMS) for advice. In this way, specialists in aviation and emergency medicine may assist from the ground.
GBMS is now is now used by most large international carriers and by virtually all United States based airlines.
Based on the condition of the passenger the captain may determine to continue the flight plan but request medical assistance upon arrival, he/she can also request expedited landing at intended destination or decide to divert the aircraft to a closer location.
Based on the condition of the passenger the captain may determine to continue the flight plan but request medical assistance upon arrival, he/she can also request expedited landing at intended destination or decide to divert the aircraft to a closer location.
Common In-Flight Medical Emergencies
An extensive U.S. study of 11.920 in-flight medical emergencies published 2013 reported that the most common event was fainting (syncope) or near fainting (presyncope), representing 37.4 percent of all cases (1).
Respiratory symptoms were the second most common medical emergency (12.1%), and nausea and vomiting came third (9.5%).
Cardiac symptoms were present in 7.7%, seizures in 5.8%, abdominal pain in 4.1%, infectious diseasses in 2.8%, agitation or psyciatric symptoms in 2.4%, allergic reactions in 2.2%, possible stroke in 2.0%, trauma in 1.8%, diabetic complications in 1.6%, and headache in 1.0%. Cardiac arrest accounted for 0.3 percent of cases.
Aircraft diversion occurred in 7.3 percent of cases; the remaining flights landed at their scheduled destinations. Aircraft diversion was most likely to happen if the event was of cardiac nature, a seizure or a possible stroke.
Of the 36 deaths identified, 30 occurred during the flight.
Onboard assistance was provided by physicians in 48.1%, and nurses in 20.1% of cases.
The most commonly used medications were oxygen (49.9%), intravenous 0.9% saline solution (5.2%), and aspirin (5%).
An automated external defibrillator (AED) was applied to 137 patients (1.3%). In most cases, it was only used to monitor heart rhythm. A shock was only delivered in five cases.
The Responsibilities of Medical Professionals on Board?
When required, the cabin crew will request medical doctors or other health professionals among the passengers to come forward to assist in managing an ill passenger. Although most physicians will respond to this request, it is well known that physicians on board may not always identify themselves, most often because they believe the problem would be outside their field of practice.
The Legal Aspects
A doctor does not have a legal obligation to step forward when assistance is requested. On the other hand, the doctor has an ethical and humanitarian duty to provide emergency care, unless circumstances prevent him/her from doing so or he/she is assured that others are willing and able to give such care (11).
By responding to the in-flight call of assistance, the doctor has taken on the role of a Good Samaritan. However, good intention does not protect against gross negligence or misconduct. The key is to do the best you can in the circumstances with the resources available, working within the limits of your competence (10).
In the US, the Aviation Medical Assistance Act of 1998 applies when a medical professional volunteers to assist. The Samaritan is protected against malpractice litigation if the following conditions are met (4):
The Samaritan is medically qualified to perform the service
The Samaritan acts voluntarily
The Samaritan acts in good faith
The Samaritan does not engage in gross negligence or misconduct
The Samaritan receives no monetary compensation (seat upgrades and travel vouchers do not count as compensation)
The Medical Care
Identifying yourself and specifying your level of training to the flight crew is an essential first step.
When assessing the patient, it is important to look for high-risk symptoms such as chest pain, shortness of breath, and signs of stroke such as weakness on one side of the body.
Patients with syncope are often unresponsive and hypotensive. However, in most cases, improvement occurs within 15-20 minutes. Oral or intravenous fluid administration is usually helpful.
A sensible initial step is to move the patient to an aisle or galley, place him/her in the supine position and administer oxygen. Give oral or intravenous fluids if possible.
Obtaining vital signs is important. Is the patient unconscious? Does he/she have a palpable pulse? Is he/she breathing normally? Blood pressure should be measured when possible.
When chest pain is considered to be of cardiac nature, consider administering aspirin. If systolic blood pressure is above 100 mm hg, consider administering sublingual nitroglycerin. If symptoms resolve with the above measures, aircraft diversion is not typically required.
If the patient is in cardiac arrest, perform CPR and obtain and apply an AED as soon as possible.
The Medical Resources On Board
There are legal requirements for the medical equipment that must be carried on board any commercial airplane. The standard is determined by the responsible aviation authority: the Federal Aviation Administration (FAA) in the United States, and the European Aviation Safety Agency (EASA) in collaboration with the Joint Aviation Authorities (JAA) in Europe.
European airlines that fly to the USA must meet the requirements of both the FAA and the JAA.
The International Civil Aviation Organization (IACO) calls for three types of medical kits; First Aid Kit (FAK), Emergency Medical Kit (EMK) and Universal Precaution Kit (UPK).
The contents of the FAK are primarily for the care of wounds and burns, but the kit may also include non-prescription medication.
Guidelines recommend that the EMK is to be used only when a medically trained doctor is available for assistance. Hence, this kit is sometimes called “the doctor’s kit”. It contains medical equipment and drugs that can be used for the clinical assessment and treatment of the passenger.
Diagnostic tools available in the EMK include a stethoscope and a sphygmomanometer. Some international aircraft have electronic blood pressure cuffs, pulse oximeters (for measurement of the oxygen saturation of blood) and glucometers (for measurements of blood glucose) in their EMK.
The UPK contains personal protection equipment for crew members and volunteer health professionals who may be exposed to communicable disease.
Most airlines also carry automated external defibrillators on board.
The majority of in-flight medical events are benign and will resolve spontaneously. Death on board is a rare occurrence.
Most events are managed by cabin crew without the assistance of an onboard health professional.
In the event of an in-flight medical emergency, a doctor is ethically obliged to help when requested. The same is true for other health professionals.
The role of the doctor is to assist and support the pilot and crew. The pilot is in command and makes the ultimate decision whether to divert the plane to another location.
The doctor should make a clinical assessment of the passenger and start necessary treatment in accordance with the resources available.
The emergency medical kit (EMK) available on board contains medical equipment and drugs that may be used for clinical examination and treatment of the passenger. The kit is to be used only when a trained medical doctor is available for assistance on the aircraft.
Most aircraft carry automatic external defibrillators (AED’s) for use in the case of cardiac arrest.
Most experts agree that diet is an important modifiable risk factor for cardiovascular disease and many other chronic noncommunicable disorders. Hence, defining and implementing a healthy diet is a matter of great public health interest. However, although there is substantial agreement on many issues, such as the importance of fruits and vegetables, several matters are still subjects of considerable controversy.
The World Health Organization (WHO) recommends that total fat should not exceed 30% of total energy intake to avoid unhealthy weight gain with a shift in fat consumption away from saturated fats to unsaturated fats and towards the elimination of industrial trans fats (1).
The importance of lowering the intake of saturated fat and replacing it with unsaturated fat, especially polyunsaturated fats was recently highlighted by a Presidential Advisory from the American Heart Association (AHA) (2). The main argument was that such a measure would “lower low-density lipoprotein cholesterol, a cause of atherosclerosis, linking biological evidence with the incidence of cardiovascular disease in populations and clinical trials”.
However, a growing number of scientists claim that the advice to restrict saturated fatty acids “is largely based on a selective emphasis on some observational and clinical data, despite the existence of several randomized trials and observational studies that do not support these conclusions” (3).
All these issues were recently highlighted by the publication of the PURE study on fat and carbohydrate intake (4,5).
The authors of the paper, lead by Mahshid Dehghan, concluded that high carbohydrate intake (more than about 60% of energy) was associated with an adverse impact on total mortality and non-cardiovascular disease mortality.
By contrast, higher fat intake was associated with lower risk of total mortality, non-cardiovascular disease mortality, and stroke. Furthermore, higher intakes of individual types of fat were associated with lower total mortality, non-cardiovascular disease mortality, and stroke risk and were not associated with risk of major cardiovascular disease events, myocardial infarction, or cardiovascular disease mortality.
Our findings do not support the current recommendation to limit total fat intake to less than 30% of energy and saturated fat intake to less than 10% of energy. Individuals with high carbohydrate intake might benefit from a reduction in carbohydrate intake and increase in the consumption of fats.
These conclusions initially appeared to shake up the world of nutrition and cardiovascular science. But, now, when the dust has settled, things seem calm as a millpond. It’s almost as if Dehghan and coworkers have had a firm slap on the wrist.
It has even been suggested by leading public health authorities that a closer look at the PURE results will reveal they do indeed not support the conclusion that nutritional advice should change (6).
Interestingly, The European Heart Network, which plays a leading role in the prevention and reduction of cardiovascular diseases in Europe, concluded that it would not be prudent to draw conclusions on what sort of level of intakes of fat, including saturated fat, and carbohydrates should be recommended for Europeans on the basis of the PURE study (7).
However, some experts see things differently. Dr. Dariush Mozaffarian, the dean of the Tufts Friedman School of Nutrition Science and Policy, said: “The PURE results provide strong support for evidence accumulating over the past decade on what makes a healthy diet. Cutting back on starch and sugar and adding more fat and more foods from plants, especially bioactive fruits and seeds, is where we should be headed (8).”
Personally, I tend to agree with Dr. Mozaffarian and I think it is imperative that the PURE data won’t be swept under the rug. However, it is important to listen to opposing arguments and those who claim that nutritional advice should remain unchanged despite PURE (or even because of PURE for that matter).
The PURE Study – A Few Opposing Arguments
The PURE study addressed the dietary intake of 135.535 individuals in 18 countries who were followed for a median of 7.4 years. The aim was to include populations that varied by socioeconomic factors. There were three high income (Canada, Sweden, and the United Arab Emirates), 11 middle income (Argentina, Brazil, Chile, China, Colombia, Iran, Malaysia, occupied Palestinian territory, Poland, South Africa, and Turkey), and four low-income countries (Bangladesh, India, Pakistan, and Zimbabwe).
The authors analyze their data by dividing macronutrient consumption into quintiles. Hence, the quintile 1 category includes the 20% with the lowest consumption and the quintile 5 category includes the 20% with the highest consumption.
Interestingly, the lowest quintile category was used as a reference group for the statistical analyses. Some experts believe this may have led to wrong conclusions. In fact, the relationship between the consumption of saturated fats and cardiovascular risk may be U-shaped and not linear. In quintile 1, which had the highest mortality, the mean consumption of saturated fat was only 2.8% of energy intake. It is argued that so little saturated fat is rarely consumed in high-income countries like the USA for example.
Associations between percentage energy from saturated fatty acids and clinical outcome. DOI: http://dx.doi.org/10.1016/S0140-6736(17)32252-3
If we look at total mortality and myocardial infarction we can see that the relationship between saturated fat consumption and clinical outcome may indeed be U-shaped. The risk is highest in quintile 1, then goes down, and starts to increase again in quintile 5 where saturated fat consumption was highest.
Using quintile 1 as a reference for the statistical comparison might be similar to using the group with the lowest BMI (body mass index) when addressing the relationship between BMI and clinical outcome. It is well known that low BMI is associated with increased risk.
So, what happens if we skip quintiles 1 and 2 because these are not applicable to western countries, and only look at total mortality, major cardiovascular disease, and myocardial infarction? In fact, we will see that quintile 3 and 4, where mean saturated fat consumption was 7.1% and 9.5% respectively, did best in terms of the clinical outcome.
However, apparently, this approach cannot explain the inverse relationship between saturated fat consumption and the risk of stroke. The more saturated fat consumed, the less the risk of stroke. I have a hard time understanding how these results may be disregarded.
It has been pointed out that total fat consumption in the lowest quintile was only about 11% of energy intake. Numbers that low are probably very uncommon in high-income countries.
In the highest quintile, which seems to do best in terms of risk, mean fat consumption was 35% of total energy intake which is above the WHO recommendation but in line with guidelines in many countries, including the Nordic countries, where the recommended fat consumption is 25-40% of energy intake. So, here it may be argued that the PURE results are concordant with current dietary advice.
Health authorities usually recommend that carbohydrate consumption should be between 45-60% of energy intake. In the lowest quintile in PURE which fared best in terms of risk, mean carbohydrate consumption was 46% of energy intake. However, mean carbohydrate consumption in quintiles 4 and 5 was, 68% and 77% respectively. While such a high carbohydrate consumption was associated with worse clinical outcome, it has been argued that it is probably uncommon in high-income countries.
The Takeaway
Many experts believe the PURE study is fraught with methodological problems, not least because of different degrees of socio-economic development in different countries.
According to the European Heart Network: “There are significant differences between diets in high-income countries and low and middle-income countries. There are also significant socio-economic differences, e.g., general health status and access to health care. Additionally, we take note that the study does not distinguish between different types of carbohydrates, i.e., complex carbohydrates rich in fiber are not distinguished from simple carbohydrates, e.g., sugars”.
Obviously, the inability to differentiate between the types of carbohydrate is a significant issue when interpreting the PURE data.
Another thing that has to be acknowledged in PURE is possible social desirability bias. In other words, individuals who are health conscious are more likely than others to adopt a healthy lifestyle. However, as the authors point out, if this were the case, there would not be different associations for different outcomes.
Furthermore, residual confounding may affect the results. Hence, the ability to afford certain foods may change the dietary pattern. For example, high-carbohydrate and low-fat diets may be associated with poverty.
However, the authors of the PURE paper point out that additional analyses adjusting for other measures of socioeconomic status (household, wealth or income) did not alter the results. Of course, the possibility of residual confounding can never be completely ruled out by such measures.
In another recently published study by the PURE investigators, it was concluded that reducing saturated fatty acid intake and replacing it with carbohydrate has an adverse effect on blood lipids. Substituting saturated fatty acids with unsaturated fats might improve some risk markers, but might worsen others. Simulations suggest that ApoB-to-ApoA1 ratio probably provides the best overall indication of the effect of saturated fatty acids on cardiovascular disease risk among the markers tested. Focusing on a single lipid marker such as LDL cholesterol alone does not capture the net clinical effects of nutrients on cardiovascular risk (9).
The PURE study leaders believe that global dietary guidelines should be reconsidered in light of the consistency of their findings together with meta-analyses of other observational studies and the results of recent randomized trials (10). However, it is quite obvious that these conclusions have not been embraced by leading public health experts in western countries.
Let me finish by Ramsden’s and Domenichiello’s final conclusion from their recent editorial published in The Lancet (3):
“The PURE study is an impressive undertaking that will contribute to public health for years to come. Initial PURE findings challenge conventional diet-disease tenets that are largely based on observational associations in European and North American populations, adding to the uncertainty about what constitutes a healthy diet. This uncertainty is likely to prevail until well designed randomized controlled trials are done. Until then, the best medicine for the nutrition field is a healthy dose of humility.”
In 1953, British researchers discovered that drivers of London’s double-decker buses were more likely to suffer a deadly heart attack than the more physically active conductors (1). Another study published five years later found that the risk of heart attack was higher among government clerks than postmen (2).
These studies laid the foundation for the hypothesis that men in physically active jobs were at lower risk of heart disease than men in physically inactive jobs. Hence, it was proposed that a sedentary lifestyle increased the risk of heart disease.
Since then it has repeatedly been shown that regular physical exercise is associated with a lower risk of premature death, coronary heart disease, certain types of cancer, and diabetes. Physical activity has also been shown to improve mental health. The World Health Organization (WHO) recently recognized physical inactivity as one of the leading global risk factors for morbidity and premature mortality (3).
However, several questions remain. What type of exercise is most likely to improve our health? Should we walk, jog, lift weights or all of those? And, is there an easy way to assess or measure our physical condition?
Physical fitness consists of cardiorespiratory fitness and muscular fitness. The American Heart Association (AHA) recommends aerobic exercises for the benefit of the heart, including walking, jogging, swimming or biking and strength and stretching exercises for overall stamina and flexibility (4).
However, strength training may have wider implications for general health than previously thought. A growing body of evidence suggests that muscular strength is inversely and independently associated with death from all causes, after adjusting for cardiorespiratory fitness and other cofactors such as age, body fat, smoking, alcohol, and hypertension (5).
Muscular Strength and Longevity
A narrative review of studies addressing the role of muscular strength as a predictor of mortality was published by German investigators in 2015 (5). Fourteen epidemiological studies fulfilled the study criteria, and all reported that an increased level of muscular strength was significantly associated with lower all-cause mortality. The same pattern was observed for cardiovascular mortality. The existed studies failed to show that low muscular strength was predictive of cancer mortality.
Grip strength is a simple and inexpensive measure of overall muscular strength.
Grip strength is a simple and inexpensive measure of overall muscular strength. It is usually performed by a Jamar hydraulic dynamometer which can measure isometric grip force with excellent reliability and reproducibility (6).
The Prospective Urban-Rural Epidemiology (PURE) study is a large, longitudinal population study done in 17 countries of varying incomes and sociocultural settings. Participants in the study were assessed for grip strength. The results of this part of the study were published in Lancet in 2015 (7).
Over a median follow-up of four years, low grip strength was associated with all-cause mortality, cardiovascular mortality, non-cardiovascular mortality, myocardial infarction, and stroke. Low grip strength was a stronger predictor of all-cause and cardiovascular mortality than systolic blood pressure.
It has been suggested that grip strength might act as a biomarker of aging across the life course (8).
The findings from the PURE study certainly suggest that skeletal muscle function is an important component of health, aging, and longevity.
Muscular Strength and Obesity
Although we are in the midst of an obesity epidemic, focusing on body weight and body mass index (BMI) may be misleading.
Of course, there is data showing a strong association between excess adiposity and increased risk of cardiovascular disease and early mortality (9).
However, substantial evidence suggests that greater aerobic fitness can lower the risk of cardiovascular disease and death associated with obesity. In a meta-analysis published 2014, overweight and obese-fit individuals had similar mortality risks as normal weight-fit individuals (10). Hence, the role of physical exercise for the treatment of obesity should not be downplayed (11).
A recent study tested the association between grip strength, obesity, and mortality (12). Data from 403.199 participants in the UK Biobank study were used in the analysis. The median follow-up was seven years.
Overall, greater grip strength was associated with an 8 percent lower risk of mortality. In contrast, adiposity measures had an inconstant association with mortality, although severe obesity (BMI>35) and abdominal obesity were strong predictors of mortality, independent of grip strength.
The mortality risk was highest for men and women with the lowest grip strength and the highest obesity measures. Interestingly, obese individuals with greater grip strength had a lower or similar mortality risks compared with nonobese people with lower grip strength.
The authors of this highly interesting paper make three important conclusions:
Men and women with greater grip strength had lower risks of mortality, independent of adiposity.
Although excess adiposity per se presents a substantial risk of mortality, the risk associated with excess adiposity was reduced, although not completely eliminated, through greater grip strength.
Overall, the findings provide compelling rationales for developing interventions and policies to improve muscular strength and reduce excess adiposity to minimize mortality risk.
Is Strength Training Associated With Mortality Benefits?
The association between grip strength and mortality does not provide proof that strength training improves health and longevity. Although the available epidemiological data is reliable, it cannot tell whether a causal relationship exists between muscular strength and mortality.
Obviously, randomized trials on the effects of strength training on mortality are difficult to perform. There would be a high risk of crossover between the groups. Furthermore, an extensive study would be needed to confirm whether or not there is a mortality benefit or not.
In a paper published 2016, US investigators found that among a large cohort of adults aged 65 or older, all-cause mortality was significantly lower among individuals who performed regular strength training (13). This was true after correcting for confounding factors.
Hence, older adults who perform strength training not only improve their physical condition, but their survival rate is improved as well. However, just like other cohort studies, this study has limited ability to determine cause and effect.
The Possible Mechanisms Behind the Effects of Strength Training
There may be several reasons why strength training and grip strength are associated with longevity.
Resistance training can counteract the age-related decline in muscle mass and strength (sarcopenia) which is characterized by a decrease in contractile protein and excessive intra-an extracellular lipid accumulation (14).
Strength training also improves neuromuscular coordination and balance. This may reduce the risk of injuries from falls which often provide serious health threats to elderly individuals.
Furthermore, resistance training increases bone mass and mineral density and lowers the risk of osteoporosis which is a global public health problem.
There is evidence that skeletal muscle in many ways acts as an endocrine organ. Skeletal muscle cells produce cytokines (myokines) that may help to fight inflammation and maintain normal body function. Hence, myokines may contribute to exercise-induced protection against several chronic diseases (15).
Strength training may also improve cardiovascular risk factors such as blood pressure, blood lipids and insulin resistance.
The Take-Home Message
There is overwhelming evidence that muscular strength and strength training are associated with several health benefits and increased life expectancy.
Older adults who perform strength training not only improve their physical condition but their survival rate is improved as well.
Obese individuals with greater muscle strength have lower risks of mortality, independent of adiposity.
Resistance training counteracts the age-related decline in muscle mass and strength, improves balance and coordination, and reduces the risk of osteoporosis.
Strength training may also reduce insulin resistance and improve blood pressure and blood lipids.
