Decline of coronary heart disease mortality in The Netherlands from 1978 to 1985: contribution of medical care and changes over time in presence of major cardiovascular risk factors.

OBJECTIVE: To study the relative contributions of medical care and changes in cardiovascular risk factors to the decline in coronary heart disease (CHD) mortality in The Netherlands from 1978 to 1985.
METHODS: The number of potential CHD deaths prevented in this period was estimated by subtracting the number of observed CHD deaths from the number of deaths that would have occurred without any change in age-specific CHD mortality. In addition, the number of myocardial infarctions over this period was determined. Using estimates of risk associated with smoking, based on national and international data, of effects of changes in total cholesterol level, of benefits of antihypertensive drug treatment and effects of different intervention strategies in subjects with a previous myocardial infarction, we calculated the relative contribution of the separate factors to the decline in CHD mortality.
RESULTS: The estimated contribution of treatment in coronary care units, postinfarction treatment and coronary bypass grafting to the fall in CHD mortality was 46%. Approximately 44% of the decline in CHD mortality could be attributed to primary prevention efforts (cessation of smoking, change in cholesterol level and treatment of hypertension).
CONCLUSION: On the basis of available estimates of the potential effects of primary and secondary prevention it seems likely that a sizeable proportion of the age-specific reduction in mortality in The Netherlands during the period 1978-85 could have resulted from these measures. However, our findings should be considered to be estimates illustrating the relative benefits of different strategies rather than absolute figures.