Commentary: risk factors or social causes?

Abstract

In many industrialized countries, there has been a welcome decline in coronary heart disease (CHD) mortality. In England and Wales, this has progressed for two decades.1 Many would like to take the credit for this decline, but the reasons for it are not entirely clear. Contributors to the decline are likely to include reductions in smoking, dietary change—but not the increase in obesity—and improvements in treatment, both of risk factors and the disease after it hits. The shadow over this bright picture is cast by the uneven nature of the improvement. In general, the higher the socioeconomic position the greater has been the improvement.2 As a result, social inequalities in CHD have increased. It is useful to keep this background in mind when considering the paper by Emberson et al. in this issue of the International Journal of Epidemiology.3 Based on analyses from the British Regional Heart Study, they argue that population wide control of risk factors—blood cholesterol, blood pressure, body mass index, cigarette smoking, alcohol, physical activity, and lung function—is a better strategy than one designed specifically to reduce social inequalities in CHD. The main reason for this conclusion is that the contribution of social class to CHD is ‘modest’. In their calculation, social class accounts for ‘only’ 22% of the CHD that occurs in a population of middle-aged British men. I must confess to having used the word ‘modest’ frequently in scientific writing. If 22% of CHD deaths can be described as modest, this literary habit needs examination. None of us in public health is in any doubt about the damage to population health caused by smoking. Indeed, the recent WHO global burden of disease study4 confirms tobacco as the single most important cause of loss of disability adjusted life years (DALYS) in developed regions of the world—and it accounts for 12.2% of lost DALYS—ultra-modest. If, and it is a rather large if, we could bring the CHD rates of men in manual occupations (the classification that Emberson et al. use) down to that of men in non-manual occupations, the 22% of all CHD deaths that would be prevented thereby, would be far from modest. It is, indeed, a large ‘if’. The argument of Emberson et al. is that we have the causes of CHD, the established risk factors, we should therefore not be diverted by concerns with social position, except possibly the high rate of smoking of those low in the hierarchy. This argument has a familiar ring. It is to be found in the excellent book of historical readings edited by Davey Smith and colleagues.5 Collis and Greenwood, writing in 1921, were discussing control of tuberculosis (consumption):