Urban-rural differences in 12 year coronary heart disease mortality: the Puerto Rico Heart Health Program.

Preliminary observations of the Puerto Rican population in 1965 indicated that the coronary heart disease mortality rate was lower than in the U.S., and that the rate in rural areas might be less than urban ones because of lower levels of cardiovascular risk factors. This prompted a prospective investigation of 8793 urban and rural men, aged 45-64 years. A 12-year mortality study has been completed with almost total follow-up. After excluding those with known coronary heart disease at baseline, age-adjusted rates for coronary heart disease, sudden, and stroke death are 19-37% higher in urban than rural men. Urban men had higher average blood pressure, cholesterol, glucose, and heart rate and were less physically active than rural men. When urban-rural differences for the known risk factors, including education and alcohol intake, are adjusted for by multivariate logistic regression analysis, no remaining significant urban-rural coronary heart disease mortality differential is present. Thus, it appears that variation in identified risk factors could explain the difference in mortality within Puerto Rico. The presence of unidentified protective factors cannot be excluded.