Importance of risk factor clustering in coronary heart disease mortality and incidence in eastern Finland

Smoking, a high serum cholesterol level and elevated blood pressure are the most important risk factors for coronary disease. Each of these major risk factors contributes independently to the risk of coronary disease, and clustering of the risk factors may increase the risk more than any of the factors alone.

This study is a 12-year prospective follow-up of 7928 men and 8530 women examined in eastern Finland. Risk factor categories were created by combining smoking status and dichotomized values of serum cholesterol level and blood pressure. Endpoints for the follow-up were either coronary death or a first coronary event (fatal or non-fatal). The effect of risk factor clustering was analyzed by assessing relative risks, mortality and incidence, and population-attributable risks in each of the risk-factor categories.

The relative risks for coronary death and first coronary event in men with all three risk factors (smoking, serum cholesterol > or = 6.5 mmol/l and either systolic blood pressure > or = 160 mmHg or diastolic blood pressure > or = 95 mmHg) were 11.8 and 7.3 respectively, compared with men with none of these factors. The corresponding risk ratios for women were 9.6 and 8.6. The 12-year coronary mortality varied between 10.0 deaths per 10000 person-years in men with none of the risk factors to 98.9 per 10000 person-years in men with all three risk factors. The 12-year incidences in men were 37.4 and 206.3 per 10000 person-years, respectively. The coronary mortality in women varied between 3.4 and 27.9 deaths per 10000 person-years and the incidence between 13.3 and 110.8 per 10000 person-years. Most of the population-attributable risk in men was associated with the combination of smoking with a high serum cholesterol level with elevated blood pressure.

The results illustrate the public-health importance of these major risk of cardiovascular diseases.