The modern history of coronary heart disease is quite remarkable. Acute myocardial infarction (acute heart attack) appears to have been relatively uncommon until it emerged in the early 1920s. Then came the plague.
In the 1950s coronary heart disease had become the most common cause of death in the industrialized world. The symptoms were often dramatic and devastating. A previously healthy person was hit by sudden excruciating chest pain, often associated with cardiac arrest and sudden death. The survivors often had damaged heart muscle, sometimes resulting in heart failure, severely compromised quality of life and a shortened life span. Coronary heart disease had become an epidemic. A major threat to public health worldwide.
In Europe and North America, the death rate from coronary heart disease reached a peak in a 15-year period between 1965 and 1980. Since then it has dropped dramatically. A 50-80% decline in mortality has been reported by many countries between 1980-2005, and the decline appears to be continuing (1,2). However, the burden of disease remains high, partly due to the aging population.
Available evidence suggests that the mortality decline is due to decreased incidence of coronary heart disease as well as better prognosis of those affected. In other words, there are fewer new cases and those affected live longer.
However, explaining these remarkable results has proven difficult. The question is whether the management of risk factors such as high blood cholesterol, smoking, and high blood pressure has been so successful or if it is the treatment that has improved?
Many researchers have used the IMPACT model (3) to examine the contributions of various factors to the decrease in death rate from coronary heart disease. This statistical model incorporates known major risk factors for coronary heart disease as well as currently used medical and surgical treatments.
IMPACT has been used to explore the contributions of risk factors and treatments in over 15 countries where mortality rates have been declining, including England, Wales, Scotland, Finland, Sweden, Italy, Spain, Iceland, Northern Ireland, New Zealand, USA and Canada. The main results of these studies suggest that approximately 40 – 75 percent of the decline in mortality is attributable to reductions in risk factors. The biggest achievement is due to reductions in total cholesterol, smoking, systolic blood pressure and physical inactivity.
Nobody will deny that from a public health perspective, these results are very impressive. The declines in smoking and saturated-fat intake and better treatment of high blood pressure are believed to be a consequence of important public health and primary care interventions (4). Obviously, great achievements have been made. So, is it time to celebrate?
The Uninvited Guest
In fact, we’ve been partying for some time now. Between the clinking of glasses and through our blurry vision, we’ve slowly discovered an uninvited guest. The intruder looks familiar, but we can’t recall where he came from or how he managed to slip through the backdoor. Or maybe he just strolled through the main entrance.
Today this intruder is a major celebrity. Everybody’s talking about him and we spot him regularly on the front page of major newspapers and magazines; television shows can’t get enough of him, and today scientists and public health experts consider him the biggest threat to public health worldwide.
Although we can’t seem to agree on the why’s and how’s, we’re suddenly confronted by a pandemic of obesity.
Many of the studies that used the IMPACT model found that the positive results were partly offset by increases in body-mass index and prevalence of diabetes, both accounting for an increased number of deaths from coronary heart disease.
A few months ago we saw an interesting and quite scary report on the global, regional and national prevalence of obesity (5). The worldwide prevalence of overweight and obesity combined rose by 27.5% for adults and 47.1% for children during the past three decades. These increases were found in developed and developing countries.
There is no reason to believe that the obesity pandemic and the consequent increase in type 2 diabetes will not adversely affect the progress made regarding the declining mortality from coronary heart disease. On the other hand, obesity may not necessarily increase the relative contribution of cardiovascular mortality because obesity is also a risk factor for other serious illnesses, such as many types of cancer and Alzheimer’s disease.
But how did this happen? How did we get so fat and metabolically sick in such a short time?
Although explaining the large increase in obesity is complex, one thing is certain; We’ve managed to create an obesogenic environment.
Most commonly, increased calorie intake and lack of physical exercise are considered the two most important contributors to obesity. But such a simple explanation is unlikely. The composition of the diet may be important as well.
Interestingly, obesity has increased in many countries at the same time as the intake of dietary fat has decreased. Most likely added sugar is partly to blame, at least in some areas of the world. In fact, the role played by sugar-sweetened beverages in the obesity epidemic is a matter of great scientific, clinical and public health interest.
Today public health experts believe that the success achieved in reducing fat consumption, saturated and trans fats in particular, has resulted in lowering of blood cholesterol in most industrialized countries. This is by many considered the main reason why the death rate from coronary heart disease has declined so rapidly.
Many experts worry that the recent increase in fat intake resulting from the popularity of carbohydrate-restricted high-fat diets may trigger a new epidemic of coronary heart disease.
However, one can’t help wondering whether the current obesity epidemic is a trade-off for lowering blood cholesterol in the population.
The widespread promotion of low-fat diets in the 1980s and 1990s led to a reduction in the percentage of calories from fat in the United States and many other countries. At the same time, the consumption of calories from carbohydrates increased.
Despite these dietary changes, the prevalence of obesity and type 2 diabetes continued to rise (6).
Or should we put it differently; Because of these dietary changes, the prevalence of obesity and type 2 diabetes has skyrocketed and become a threat to public health.
Although increased carbohydrate and reduced fat consumption may have lowered total and LDL cholesterol (the bad cholesterol), there are some serious concerns. High-carbohydrate diets reduce HDL cholesterol (the good cholesterol) and raise blood concentrations of glucose, insulin, and triglyceride and blood pressure, contributing to the now well-recognized metabolic syndrome, sometimes called insulin resistance syndrome, that is known to increase the risk of coronary heart disease and type 2 diabetes.
If public health authorities claim their interventions made an important contribution to lowering coronary heart disease mortality, their interventions or lack thereof may be responsible for the pandemic of obesity. It happened on the same watch, didn’t it?
It is time public health authorities critically evaluate the consequences of the dietary recommendations of the last thirty years. Needless to say, the effects on the food industry have been astonishing. For years, low-fat products have been highlighted as a symbol for good health. Everything that possibly can raise blood cholesterol is associated with danger. Dairy fat, eggs and red meat have been demonized.
Although we can certainly allow us to celebrate our success in preventing and treating coronary heart disease, it’s time to face the darker side. Obesity and diabetes are the new threats. It’s time to meet with the uninvited guest.