Time trends in incidence rates of venous thromboembolism in a large cohort recruited from the general population

Changes in the incidence of venous thromboembolism (VTE) during the last two decades have not been extensively studied. Therefore, we studied time trends in the incidence rates (IRs) of deep vein thrombosis (DVT) and pulmonary embolism (PE) in a cohort of 26,855 subjects, aged 25-97 years, enrolled in the Tromso study in 1994/1995. The subject were followed-up throughout 2012, and all symptomatic, objectively confirmed, incident VTEs were identified using multiple sources (hospital discharge-, radiology procedure- and autopsy registry) and validated by review of medical records. Age-adjusted biennial IR per 100,000 person years (PY) with 95% confidence intervals (CI) were calculated using Poisson regression. Between January 1996 and December 2012, 693 VTEs occurred during 368,150 PY of follow up. The IR of VTE increased from 158 (95% CI 116-199) in 1996/1997 to 201 (95% CI 160-243) in 2010/2011. There was a marked increase in the rates of PE (with/without concurrent DVT) ranging from 45 (95% CI 23-67) in 1996/1997 to 113 (95% CI 82-144) in 2010/2011, whereas the rates of isolated DVT decreased (112, 95% CI 77-146 in 1996/1997 and 88, 95% CI 61-115 in 2010/2011). Despite advances in prophylaxis, the IR of VTE has increased slightly during the last 15 years, mainly due to an increase in PE. Although the introduction of better diagnostic tools to some extent may explain the increase in PE rates, our findings suggest that there is still a need for improvement in risk factor management and prevention strategies of first time VTE.