Results:

During 6 years’ follow-up of 1,162,718 women (mean age 56 years), 4,630 were admitted to the hospital for or died of VTE. One-half of the cohort had never smoked (51%), whereas 28% were past smokers and 20% were current smokers at recruitment, with similar proportions smoking <15 and ≥15 cigarettes per day. The proportion of women in the lowest socioeconomic tertile increased from 27% in never-smokers to 51% in current heavy smokers. Smokers (past and current) were more likely to be current users of hormone replacement therapy than never-smokers, but current smokers were less likely to exercise regularly or to have a history of hypertension at recruitment. In the absence of surgery, current smokers had a significantly increased incidence of VTE compared with never-smokers (adjusted relative risk [RR], 1.38; 95% confidence interval [CI], 1.28-1.48), with significantly greater risks in heavier than lighter smokers (RR, 1.47; 95% CI, 1.34-1.62 and RR, 1.29; 95% CI, 1.17-1.42 for ≥15 vs. <15 cigarettes per day). Current smokers were also more likely to have surgery than never-smokers (RR, 1.12; 95% CI, 1.12-1.13). Among women who had surgery, the incidence of VTE in the first 12 postoperative weeks was significantly greater in current than never-smokers (RR, 1.16; 95% CI, 1.02-1.30).