Testicular

Abstract

EDrTOR,-M R Law and colleagues' findings' 2 are encouraging for those engaged in health promotion. Their findings do not, however, necessarily solve the real concerns of the public. Many people ask their doctor how to reduce the risk of heart attacks, but their real concern is how to live a longer and healthier life. If these major reductions in heart disease were matched by an equally impressive lengthening of the lifespan we could wholeheartedly advocate the measures recommended. There have been suggestions that the gain in healthy years may be more modest. Several years ago I tried to solve this problem by computer modelling.3 I used age specific mortality for Australia for 1984 and assumed that (a) lowering the serum cholesterol concentration would reduce the cardiac mortality to that ofmen naturally at this lower level; (b) the relative risks for cholesterol concentrations were the same at all ages; and (c) lowering the serum cholesterol concentration did not affect mortality from other causes. There were two main results from this modelling exercise. The first was a dramatic change in the causes of death. With the present range of serum cholesterol concentrations the model predicted that 47% of deaths would be due to heart disease, 27% to cancer, and 26% to other causes. This is close to the actual figures at the time. If all cholesterol concentrations were reduced by 10% the model predicted that 42% of deaths would be due to heart disease, 30% to cancer, and 28% to other causes while the median lifespan would be increased by one year. Reducing the cholesterol concentration of all people to within the range of the present lowest fifth of concentrations would result in 33% of deaths being due to heart disease, 34% to cancer, and 33% to other causes while the median lifespan would be increased by three years. A reduction in the mean cholesterol concentration by 10% is an achievable goal, but the gain is only one extra year of life. The major reduction in cholesterol concentrations is not a practical goal. Computer modelling is inferior to analysis of data and should be used to generate hypotheses rather than test them. Law and colleagues have used their data to find the changes in the causes of death with changes in cholesterol concentrations. With little extra analysis their data could also be used to show the effect of reduced cholesterol concentrations on lifespan. Could I persuade them to do the analyses to answer questions about changes in lifespan, which are important (dare I say vital) for practising clinicians and health educators?