MedWire News: Smoking is an independent risk factor for venous thromboembolism (VTE) among middle-aged men and women, show results of a large prospective study.
However, “former smokers have the same risk for VTE as never smokers, indicating acute effects of smoking, and underscoring the potential benefits of smoking cessation,” write Marianne Severinsen (Aarhus University Hospital, Aalborg, Denmark) and colleagues in the journal of Thrombosis and Haemostasis.
To assess whether smoking is associated with VTE independently of established risk factors, Severinsen and team followed up 27,178 men and 29,875 women, aged 50 to 64 years, who were participating in the Danish Diet, Cancer, and Health study.
During a median follow-up of 10.2 years, there were 617 verified VTE events in the Danish National Patient Registry. Of these, 58% were deep vein thrombosis and 42% were pulmonary embolism (PE). A further 24 PE events were identified by autopsy.
After adjusting for alcohol intake, body mass index, physical activity, and use of hormone replacement therapy in women, the researchers found that women who smoked had a 52% increased risk for VTE compared with women who had never smoked, while men who were smokers had a 32% increased risk for VTE.
The team also found that the risk for VTE increased with increasing doses of tobacco. Women who smoked more than 20 g of tobacco per day and men who smoked more than 30 g per day had a 150% to 300% increased risk for VTE, whereas lower rates of tobacco consumption were associated with only a 10% to 40% higher risk for VTE compared with never smokers. Of note, former smokers had the same risk for VTE as people who had never smoked.
“Our findings suggest a direct effect of heavy smoking on the risk for VTE,” remark Severinsen and co-authors. “These findings are biologically plausible because smoking increases the level of coagulation factors in the blood and it also promotes activation of the inflammatory system, both of which are found to be associated with venous thrombosis.”
“However, as in all observational studies, we cannot completely rule out possible confounding by unknown factors,” the researchers add.
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