Joint effect of ischemic stroke and obesity on the risk of venous thromboembolism: the Tromsø Study.

Background: Patients with ischemic stroke have increased risk of venous thromboembolism (VTE). Obesity is prevalent in stroke patients and a well-established risk factor for VTE. Whether obesity further increases the VTE risk in patients with stroke remains unclear.

Objectives: We investigated the joint effect of ischemic stroke and obesity on the risk of incident VTE in a population-based cohort.

Methods: Participants ( = 29,920) were recruited from the fourth to sixth surveys of the Tromsø Study (1994-1995, 2001, and 2007-2008) and followed through 2014. Incident events of ischemic stroke and VTE during follow-up were recorded. Hazard ratios (HRs) of VTE with 95% CIs were estimated according to combined categories of ischemic stroke and obesity (body mass index ≥ 30 kg/m), with exposure to neither risk factors as reference.

Results: During a median follow-up of 19.6 years, 1388 participants experienced ischemic stroke and 807 participants developed VTE. Among those with stroke, 51 developed VTE, yielding an incidence rate of VTE after stroke of 7.2 per 1000 person-years (95% CI, 5.5-9.5). In subjects without stroke, obesity was associated with a 1.8-fold higher VTE risk (HR, 1.76; 95% CI, 1.47-2.11). In nonobese subjects, stroke was associated with a 1.8-fold higher VTE risk (HR, 1.77; 95% CI, 1.27-2.46). Obese subjects with stroke had a 2-fold increased VTE risk (HR, 2.44; 95% CI, 1.37-4.36).

Conclusion: The combination of obesity and ischemic stroke did not yield an excess risk of VTE. Our findings suggest that obese subjects with ischemic stroke do not have a more than additive risk of VTE.