A prospective study of risk factors for pulmonary embolism in women.

OBJECTIVE: To investigate risk factors for pulmonary embolism in women.
DESIGN: Prospective study based on biennial, mailed questionnaires.
SETTING: Nurses' Health Study with 16 years of follow-up from 1976 to 1992. PATIENTS: A group of 112822 women aged 30 to 55 years in 1976, free from diagnosed cardiovascular disease or cancer at baseline. Overall, there were 1619770 person-years of follow-up. MEASUREMENTS: Based on self-report and medical records, we documented 280 cases of pulmonary embolism, of which 125 were primary (no identified antecedent cancer, trauma, surgery, or immobilization). Information on height, weight, cigarette smoking, hypertension, diabetes, and hypercholesterolemia was collected by questionnaire.
RESULTS: In multivariate analysis, obesity, cigarette smoking, and hypertension were independent predictors of pulmonary embolism. Specifically, obese women (body mass index > or = 29.0 kg/m2) had an increased risk of primary pulmonary embolism (multivariate relative risk=2.9; 95% confidence interval [CI], 1.5-5.4). Heavy cigarette smokers also had an increased risk of primary pulmonary embolism. The relative risk (RR) of primary pulmonary embolism was 1.9 (95% CI, 0.9-3.7) for women currently smoking 25 to 34 cigarettes per day and 3.3 (95% CI, 1.7-6.5) for those smoking 35 cigarettes or more daily as compared with never smokers. Hypertension, even after adjustment for body mass index, was also associated with an increased risk of primary pulmonary embolism (RR=1.9; 95% CI, 1.2-2.8). High serum cholesterol levels (RR=1.1; 95% CI, 0.62-1.8) and diabetes (RR=0.7; 95% CI, 0.3-1.9) did not appear to be related to primary pulmonary embolism.
CONCLUSION: These prospective data indicate that obesity, cigarette smoking, and hypertension are associated with increased risk of pulmonary embolism in women. Control of these risk factors will decrease risks of pulmonary embolism as well as coronary heart disease.