How can we best prolong life? Benefits of coronary risk factor reduction in non-diabetic and diabetic subjects.

OBJECTIVE

To compare the theoretical benefits of different approaches to reduce risk factors for coronary heart disease in subjects at risk.

DESIGN

The results of findings from meta-analyses of intervention studies on cause specific mortality and of observational studies on smokers and ex-smokers were applied to observational data on 10 year cause specific mortality derived from the multiple risk factor intervention trial. Lifetable analyses were used to estimate gains in life expectancy.

SUBJECTS

Diabetic and non-diabetic men initially 35-57 years of age.

MAIN OUTCOME MEASURES

10 year mortality from coronary heart disease, 10 year total mortality, man years of intervention to prevent one death and one death from coronary heart disease, gain in life expectancy, and drug costs per year of additional life in diabetic and non-diabetic men of 45.

RESULTS

In non-diabetic men a 10 year mortality from coronary heart disease of 14.4 per 1000 would be reduced by a mean of 0.58, 0.82, 2.64, and 2.74 per 1000 by antihypertensive treatment, lowering cholesterol concentration, taking aspirin, and stopping smoking respectively; a 10 year total mortality of 44.1 per 1000 would fall by a mean of 1.06, 5.16, and 8.65 per 1000 with antihypertensive and aspirin treatment and stopping smoking respectively and increased by a mean of 0.07 per 1000 with the lowering of cholesterol concentration. In diabetic men the reductions in mortality from coronary heart disease would be between three and five times greater, and total mortality would show mean reductions of 5.81, 0.56, 16.17, and 20.84 per 1000 respectively, with all interventions of significant benefit except the lowering of cholesterol concentration. Between 2400 and 3800 man years of pharmacological intervention were calculated as being necessary to prevent one death from coronary heart disease in a non-diabetic man, and between 800 and 1200 man years in a diabetic man. The loss of life expectancy associated with smoking and hypertension is greater than that accruing from hypercholesterolaemia, but stopping smoking would prolong life by a mean of around four years in a 45 year old non-diabetic man and three years in a diabetic man, whereas aspirin and antihypertensive treatment would provide approximately one year of additional life expectancy in both categories.

CONCLUSIONS

Studies to date have shown little impact of drugs that lower cholesterol concentration and blood pressure on either coronary heart disease or total mortality. Although new treatments for hypercholesterolaemia and hypertension might help prevent coronary heart disease, other approaches to reduce the burden of premature death are required.