Twenty-five-year coronary mortality trends in the seven countries study using the accelerated failure time model

Abstract

The ‘accelerated failure time model’ (AFT) was tested in the 25-year experience of the Seven Countries Study, to describe the shape of hazard for coronary heart disease (CHD) mortality during long-term follow-up. Sixteen cohorts of men aged 40–59 at entry were enrolled in eight countries (USA, Finland, The Netherlands, Italy, Croatia, Serbia, Greece and Japan) for a total of 12,763 subjects. Risk factors were measured and CHD mortality data collected during 25 years. The AFT incorporating the Weibull survival distribution was applied to the pooled cohorts of each country, with CHD mortality as end-point. Cumulative hazards and the annual hazard for CHD mortality were estimated during 25 years and compared among countries. The annual hazard for CHD in 25 years tended to reduce relatively or flatten out in the northern American and northern European countries, exponentially increased in Serbia and Japan, and increased moderately in the other countries of southern Europe. Positive correlations were found between the shape of the hazard curve and population mean risk factor changes (serum cholesterol and systolic blood pressure) observed during the first 10 years follow-up. The Japanese group was an outlier. The countries with the largest relative decline in the annual hazard function were the same where, during the same historical period, the largest decreases in official death rates from CHD were recorded and vice versa. The curve shape in the annual hazard for CHD mortality in different countries seems related to changes in mean levels of serum cholesterol and systolic blood pressure.