Urban-rural differences in coronary heart disease in a low incidence area. The Puerto Rico heart study.

This report explores coronary heart disease (CHD) risk factors and the incidence of new CHD events developing over a two and one-half year period in 8793 urban and rural Puerto Rican men aged 45--64 years. Rural men had a lower average blood pressure, serum cholesterol, blood sugar, heart rate and relative weight than urban men. They were more active physically and although more of them smoked, they smoked fewer cigarettes than urban dwellers. The age-adjusted CHD incidence rate for urban men was 1.5 times that of rural men. Among rural areas the most rural had the lowest incidence. Among urban areas there was a suggestive trend of increasing incidence with degree of urbanization. Differences in conventional risk factors, while substantial, do not entirely explain the modest differences in incidence. There also appeared to be a relation with geographic mobility. Urban men who had always lived in the same area had an incidence rate as low as that for rural men whereas recent rural migrants to urban areas had the highest rates of all.