A physically active lifestyle--public health's best buy?

Leaders A physically active lifestyle public health's best buy? Times have changed. Many people spend most of their working time in the office, sitting behind computer terminals , PCs or laptops. Death is no longer from a mono-causal, infectious disease, but by multi-causal chronic diseases. Lifestyle factors, such as smoking, excessive alcohol intake, nutrition (for example, a too high intake of dietary fat or an excessive intake of polysaturated fatty acids, or both) and physical inactivity, play an important part in the aetiology of such chronic diseases, like coronary heart disease (CHD), hypercholesterolaemia, hyperten-sion, stroke, non-insulin dependent diabetes mellitus (NIDDM), and certain forms of cancer. The first three factors are considered "classic" independent risk factors for multi-causal chronic disease. The role of physical inactivity as an independent lifestyle risk factor has been the subject of debate and controversy. This debate seems, however, to have come to an end with the publication of consensus statements1-3 and policy documents" on the health benefits of a physically active lifestyle. Not only will the individual person's health benefit from a reduced risk of the chronic diseases mentioned above but the public health status of a nation will benefit tremendously from a physically active lifestyle. The public health burden of a sedentary lifestyle can be quantified by calculating the population attributable risk (PAR) of such a lifestyle. PAR is an estimate of the proportion of the public health burden caused by a particular risk factor, for example , a sedentary lifestyle. By calculating PAR we may estimate the proportion of deaths from chronic diseases (CHD, NIDDM, cancer, etc) that would not occur if everyone in a population was sufficiently physically active.7 To calculate PAR, we need to know the relative risk (as a measure of the strength of the relation between a risk factor and the public health burden) and the prevalence of the risk factor. The "true" relative risk is constant because it is biologically determined and will therefore not change, even though estimates of relative risk may change because of improvement of scientific measurement.7 Consequently changes in PAR are highly dependent on changes in prevalence and not on changes in relative risk. Based on available information on both relative mortality risks and preva-lences of a sedentary lifestyle Powell and Blair7 estimated the PAR of sedentary living for mortality from CHD, colon cancer, and diabetes mellitus to be 35%, 32%, and 35% respectively, meaning …