Many people believe that visiting the doctor regularly will prevent problems. Diseases may be diagnosed and cured early, before they cause harm. We have our cars checked on a regular basis. Why shouldn’t the same apply to our bodies?
But are general health checks really helpful? Putting it differently; could health checks possibly be harmful? Will they lead to unnecessary diagnostic and therapeutic interventions, possibly causing harm?
Why should you visit your doctor if you are feeling good and have nothing to complain about?. There may be a few reasons.
Firstly, you may want to have a general health check, look for hidden problems, a ticking time-bomb. Early stage cancer, high blood pressure, diabetes or heart disease. There are endless possibilities.
Secondly, you might want advice from your doctor. What can I do to improve my health? What should I eat? How much should I exercise? How can I cut my risk of being hit by cancer or heart disease?
Thirdly, you may simply be looking for the euphoria and feeling of security when your doctor tells you that everything is fine, although that’s not necessarily true because health checks have severe limitations when it comes to ruling out disease.
General health checks are commonly recommended for screening. They aim to detect problems and risk factors with the purpose of preventing disease and lower mortality. However, whether the medical check-up is helpful or effective is a matter of debate. Of course, this may sound strange and counterintuitive. How could it not be good visiting your doctor regularly?
In a recent review of randomized trials comparing health checks with no health checks, general health checks did not reduce the risk of death, neither overall nor for cardiovascular or cancer causes. So. if screening does not do more good than harm, should it be performed?
The Inter99 Trial
In 1999 Danish researchers started the Inter99 Trial, a very large and ambitious randomized study to address the question whether systematic screening of risk factors for heart disease followed by repeated lifestyle counseling would affect the development of coronary heart disease on a population level. The results, which are highly interesting and relevant, were recently published in The BMJ.
A total 61.301 people in the Copenhagen area were randomized to an intervention group or a control group and followed for ten years. People allocated to the intervention group were invited to the Research Centre for Prevention and Health and were screened with a comprehensive questionnaire, physical measurements, blood sample and glucose tolerance test.
Individuals were stratified as high and low risk. Factors such as daily smoking, high systolic blood pressure, high cholesterol, obesity, and diabetes were used to define high risk. In total, 60% of the participants were defined as high risk.
The intensity of lifestyle counseling was based on the risk estimate. Counseling was primarily targeted to those who were daily smokers, had less than 30 minutes physical activity per day, had a diet dominated by high intake of saturated fat, consumed less than 300 g of fruit and vegetables daily, or had an alcohol consumption above the recommended maximum levels.
The authors have already published results showing that after five years of counseling, lifestyle improved markedly in the intervention group, with a substantial reduction in the prevalence of smoking, improved dietary habits, increased physical activity, and a decrease in binge drinking.
If our understanding of the relationship between risk factors and heart disease is correct, we would certainly expect this to lead to less risk for coronary heart disease and lower mortality. However, the main findings of the Inter99 Trial were that after ten years, a similar number of people had developed coronary heart disease and stroke in the intervention and control groups respectively. Furthermore, there was no difference in total mortality between the groups.
Why Doesn’t Risk Factor Screening and Lifestyle Counseling Work?
The authors highlight some of the possible explanations for their results. Is a 10-year follow-up too short? Possibly, a general practice might be a more suitable place for lifestyle intervention. Maybe general practitioners are good at finding high-risk patients and implementing lifestyle counseling when it’s proper. This could explain why the control group fared equally well as the intervention group.
There can be many other reasons for the lack of effect. The authors have pointed out that people from the lower social classes, with the unhealthiest lifestyle and the highest risk of heart disease, were under-represented. Another explanation could be that many participants returned to their usual unhealthy lifestyle habits after the five-year intervention period. This has not been shown to be the case, but I understand that this question is presently being analyzed by the authors.
In an accompanying editorial in The BMJ, Peter Gøtzsche and coauthors point out that the beneficial effects of screening could be canceled out by harmful ones. Many commonly used interventions don’t have proven benefit. An example they give is the fact that drug regulators approve diabetes drugs solely based their ability to lower blood sugar, without really knowing what else they do. In fact, some diabetes drugs have been shown to increase the risk for coronary heart disease.
In a previous paper, the Inter99 Trialists reported that at a 5-year follow-up the intervention group compared to the control group had significantly increased their intake of vegetables and decreased the intake of saturated fats.
Significant effects on fruit and fish intake were found at the 3-year follow-up, but the effect was less at the 5-year follow-up.
The authors concluded that their multi-factorial lifestyle intervention promoted beneficial long-term dietary changes and highlighted that the intake of vegetables and saturated fat was improved.
Inevitably, this raises another question. Was correct lifestyle counseling given? Were the right targets chosen? Is reducing intake of saturated fats and increasing intake of vegetables always beneficial?
Could some part of the study population have benefited from another approach? Could carbohydrate restriction allowing more consumption of dietary fats have benefited those with obesity or the metabolic syndrome?
The Bottom Line
The authors conclude that systematic screening of the general population for high risk followed by lifestyle counseling has not in this and all previous similar studies been able to reduce the incidence of coronary heart disease. Therefore, lifestyle counseling should not be implemented as a systemic program in the general population, and should not be part of a country’s health policy.
It may be hard to for us to understand the results of the Inter99 Trial. One of the reasons I find this study so important is that it highlights many important characteristics of clinical trials, both their strengths and limitations. It is important to understand that a clinical trial is designed to answer a certain question. Therefore, the results may never be taken out of context and used to answer different questions.
The study does not prove that visiting your doctor for a health check and advice is useless. It does not prove that lifestyle interventions on an individual basis are ineffective. However, the results definitively indicate that targeting large numbers of people with systematic screening and lifestyle counseling does not offer any measurable benefit. The conclusion of the paper tells it all:
Lifestyle counseling should continue in everyday practice but should not be implemented as a systemic program in the general population.