International Task Force for Prevention of Coronary Heart Disease

International Task Force for Prevention of
Coronary Heart Disease

CORONARY HEART DISEASE: REDUCING THE RISK

The salient fact underlying prevention strategy in older persons is that the incidence of CHD is very high in this growing population group. Hence, even a small percentage lowering of risk translates into a considerable reduction in the number of CHD events and is a function of the relative risk and the incidence of the disease. The potential for prevention is therefore large.

The classical risk factors continue to operate after age 60 years. To understand why this was not realised for many years, it is necessary to distinguish "relative" from "absolute" risk. The former is the fraction (or percentage) by which the incidence of a disease is increased by a risk factor, (e.g. diabetes confers 2.5-fold relative risk of CHD). Absolute risk is the effect of a risk factor on the incidence of certain event, and is estimated by multiplying the relative risk by the incidence of the disease. In many studies the relative risk conferred by classical risk factors becomes smaller in older age groups, but because of the high background incidence of CHD the absolute risk is as great or in some studies even greater than in younger groups.

In persons aged 60 and over, plasma cholesterol level, systolic blood pressure, cigarette smoking, HDL-cholesterol and to a lesser extent body mass index have all been shown in large scale longitudinal studies (e.g. Framingham study, the Honolulu Heart Program and in Chicago population cohorts) to predict increased incidence of CHD. Recently evidence has been reported from clinical trials that risk factor reduction lowers CHD incidence. The treatment of hypertension in older persons is of established benefit, as previously discussed. By subset analysis a reduction in recurrent CHD events was seen in persons aged over 60 years in the 4S secondary prevention trial of cholesterol lowering by simvastatin. A smaller institutional trial of a lipid lowering diet, the Veterans Administration study, showed that lowering of elevated cholesterol levels was as effective in reducing the incidence of cardiovascular events in the over-60s as in younger participants.

To some extent, doubts concerning prevention in the elderly may have stemmed from the belief that once atherosclerosis became established, interventions were unlikely to alter its inexorable natural history. Currently, a wealth of angiographic trials have made it clear that, at least in the case of LDL-cholesterol lowering, the progression of even advanced atherosclerotic plaques can be slowed. In many trials, partial regression of such lesions was identified (Table 9).

Beyond age 85 years, high plasma cholesterol concentrations are associated with increased life expectancy because undiagnosed cancers and infections lower cholesterol levels. The effects of cholesterol-lowering therapy have yet to be assessed in this age group.

Risk factor in-ter-vention in older persons needs attention to some specific issues. Quality of life is one: intervention is most appropriate in older per-sons in good general health, able to enjoy life (the "biologically young") and with reasonable life expectancy. Dietary change needs to take food preferences and eating difficulties into account, to be gradual, and to maintain a nutritionally sound combination of foods. Untoward effects of drugs are a particular problem e.g, postural hypotension from anti-hyper-ten-sives, constipation and dyspepsia from statins and resins; differences in drug metabolism may ne-cessitate lower dosage. Drug costs can be a further source of difficulty. Because of the large number of drugs used by older persons, drug interactions are of especial concern.