Does Smoking Increase Risk for Venous Thromboembolism?

Smoking increases the risk for arterial thrombosis, but evidence that it increases the risk for venous thromboembolism (VTE) is conflicting. Now, two new studies indicate that smoking does increase VTE risk, but only if other risk factors are present.

In a single-center, prospective, population-based, cohort trial (the Tromsø study), investigators in Norway enrolled >24,000 persons and followed them for a median of 12.5 years. Compared with nonsmokers, heavy smokers (>20 pack-years) had higher risk for VTE (hazard ratio, 1.46; 95% confidence interval, 1.04–2.05). The elevated risk in smokers occurred only with provoked VTE (in conjunction with surgery, cancer, or other acute medical conditions) and increased with more pack-years of smoking. …