[A 20-year prospective study on risk factors for myocardial infarction of 5,137 men in Capital Steel and Iron Company]

Abstract

Objective: To identify independent risk factors for myocardial infarction (MI) in Chinese men and to develop a model to predict risk profile of an individual suffering MI.

Methods: Study sample included 5 137 men aged 45.2 +/- 7.8 years who came from a cohort in Beijing Capital Steel and Iron Company, based on the three surveys on coronary heart disease conducted in 1974, 1979 and 1980, respectively. Demographic data and other risk factors, such as life style, medical history, blood pressure, total serum cholesterol level (TC), etc. were collected according to the same protocol in 1980. All the participants were followed up for MI in an average period of 20.84 years until 2001.

Results: (1) There were 122 cases with MI identified during the period of follow-up, with an incidence of MI 117.4 per 100 000 person-years. Age of more than 50, smoking, higher systolic and diastolic blood pressure (SBP and DBP) levels, higher TC all were identified as important risk factors of MI. (2) Incidence of MI increased with TC. An increment of 0.52 mmol/L of TC significantly increased relative risk of MI by approximately 40% after adjusted for age, blood pressure and smoking. (3) An increment of 20 mm Hg in SBP or 10 mm Hg in DBP associated with a 40% increase in incidence of MI, adjusting for age, TC and smoking. (4) Smoking was the most risky factors for MI. Smokers had 2.3 times risk of MI, after as compared to non-smokers (or its incidence increased by 137%), after adjusting for blood pressure, TC and age, etc. (5) Incidence of MI increased by 20% with increment of five-year of age in those aged over 50 (P < 0.05), after adjusting for blood pressure, TC and smoking. And, (6) finally, based on multivariate logistic and Cox regression analyses, a model containing several risk factors, such as age, blood pressure, TC and smoking, was developed to predict individual's risk for afflicting MI.

Conclusions: Results of this prospective study showed several established risk factors for MI, including age, blood pressure, TC and smoking all as independent predictors of MI in Chinese men. It is clear and rational that intervention and modification of those traditional risk factors can lead to a decrease in coronary events in Chinese population.