Smoking, Surgery, and Venous Thromboembolism Risk in Women: United Kingdom Cohort Study

Study Questions:

Is smoking associated with venous thromboembolism (VTE) risk around the time of surgery?

Methods:

Data from the Million Women Study, a prospective cohort study of 1.3 million women through the National Health Service (NHS) Breast Screening Program (in England and Scotland) were used for the present analysis. Women were enrolled between 1996 and 2001. Information on smoking status and amount currently smoked, as well as use of hormone replacement therapy, height and weight, physical activity, alcohol consumption, medical and reproductive history, use of oral contraceptives, education, and other factors was collected for study participants. Women with a history of previous VTE, clotting disorder, cancer, surgery in the 12 weeks before recruitment, or loss to NHS follow-up before study entry were excluded. Also excluded were those with missing information on smoking. Participant information allowed linkage to national registries, which captured information on hospital admissions. Women were classified as never, past, or current smokers as reported at recruitment; current smokers were further classified according to the average number (<15, ≥15) of cigarettes smoked per day. Women were classified as having a VTE if they had either a hospital admission record or death registration with an ICD code related to a VTE event.

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).

Conclusions:

The investigators concluded that VTE incidence was increased in current smokers, both in the absence of surgery and in the 12 weeks after surgery. Smoking is another factor to consider in the assessment of VTE risk in patients undergoing surgery.

Perspective:

These data suggest an increased risk of VTE related to smoking. These data add further evidence regarding the benefits of smoking cessation, including reducing postoperative risk of VTE incidence.

Clinical Topics: Diabetes and Cardiometabolic Disease, Prevention, Pulmonary Hypertension and Venous Thromboembolism, Vascular Medicine, Exercise, Hypertension, Smoking

Keywords: Great Britain, Neoplasms, Contraceptives, Oral, Exercise, Venous Thromboembolism, Smoking, Postoperative Period, Ubiquitin-Protein Ligases, Cardiology, Cardiovascular Diseases, Motor Activity, Tobacco Use Disorder, Hormone Replacement Therapy, Hypertension, Smoking Cessation


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