Obesity Is a Risk Factor for Recurrent Venous Thrombosis in Young and Middle-Aged Women. Results From Tehs-Follow up, a Nested Cohort Study On 1394 Women with VTE.

Venous thromboembolism (VTE) is a multifactorial disease with a high risk of recurrence. The risk of recurrence is highest during the first year with an incidence of 10–15%, thereafter recurrence occurs in 3 to 5 % per year. The risk of recurrence is associated with age, gender and whether the first VTE was provoked by a transient risk factor or not. Obesity increases the risk of a first event of VTE but its role for a recurrent event is unclear.

We performed a nested cohort study and included 1394 women 18 to 64 years of age with a previous first episode of deep vein thrombosis (DVT) located in the leg or pelvis or with a pulmonary embolism (PE). All women had taken part in TEHS, a population based case-control study on risk factors for VTE. Information on risk factors was obtained by interviews and DNA-analyses immediately after the VTE and information of recurrent VTE was obtained from a follow-up questionnaire or from data recorded in the Swedish Patient Register. Only women who were not on continues anticoagulant treatment were included for assessment of recurrent VTE. Women with a BMI ≥ 30 were considered obese. Risks of recurrence were calculated in Cox regression models and are presented as hazard ratios (HRs) with 95% confidence intervals.

A total of 964 women (mean age 46 ± 13 years) with a median follow-up of 76 months accepted participation in the nested cohort study. The recurrence rate was 10.3% and 221 women (23%) were obese when diagnosed with their first VTE. At follow up 240 women (25%) were obese. The recurrence rate was higher in obese than in non-obese women (15.8% vs. 8.6%, p=0.002). The HR for recurrence was 1.9 (p=0.02, 95% CI 1.3–2.9) for obese women compared to non-obese. The HR was unchanged in a multivariate analysis, adjusting for age, index VTE (provoked or unprovoked by cast/surgery or hormonal treatment) and presence of factor V Leiden or prothrombin gene mutation.

Obesity is a strong independent risk factor for recurrent VTE in women. Obese women with a first VTE might benefit from long time treatment with anticoagulants and consultation on weight reduction.

No relevant conflicts of interest to declare.