Response to letter regarding article, "Impact of incident venous thromboembolism on risk of arterial thrombotic diseases".

BACKGROUND Growing evidence supports an association between venous thromboembolism (VTE) and arterial thrombotic diseases (ie, myocardial infarction and ischemic stroke). We aimed to study the association between VTE and future arterial events and to determine the population attributable risk of arterial events by VTE in a large prospective cohort recruited from the general population. METHODS AND RESULTS In 1994 to 1995 and 1993 to 1997, 81 687 subjects were included in the Tromsø Study and in the Diet, Cancer and Health Study and followed up to the date of incident venous and arterial events (myocardial infarction or ischemic stroke), death or migration, or to the end of the study period (2010 and 2008, respectively). There were 1208 cases of VTE and 90 subsequent arterial events during a median follow-up of 12.2 years. An association between VTE and future arterial events was found in all women and men aged <65 years but not in men aged >65 years. Women <65 years old with VTE had 3.3-fold higher risk of arterial disease (adjusted hazard ratio, 3.28; 95% confidence interval, 1.69-6.35) compared with women of the same age without VTE. The corresponding hazard ratio in men aged <65 years was 2.06 (95% confidence interval, 1.32-3.20). Only 0.9% of the arterial events were attributed to VTE, and the VTE explained 63.8% of the risk of arterial events among VTE patients. CONCLUSIONS Our findings imply that women and young men with VTE have higher risk of arterial thrombotic disease than those without VTE. However, only 1% of the arterial thrombotic events in the population are attributed to VTE.