Multiple sclerosis and the incidence of venous thromboembolism: a systematic review and meta-analysis.

A number of studies have suggested that multiple sclerosis (MS) can be associated with serious vascular complications, for which pulmonary thromboembolism (PTE) is a potentially lethal complication. The purpose of this study is to establish a current literature-based estimate of the incidence of venous thromboembolism (VTE), deep vein thrombosis (DVT), and PTE in patients with MS (pwMS) due to the lack of systematic reviews and meta-analyses on this topic. In this systematic review and meta-analysis, studies were assessed regarding the association between MS and the incidence of VTE. The studies were identified through a systematic search of major electronic databases spanning the period from 1950 to February 2022. A random-effects analysis was conducted to calculate the pooled effect size (ES) and 95% confidence intervals (CI) using STATA software. Nine out of 4605 studies were included in the meta-analysis, with an overall sample size of 158,546 individuals. Meta-analysis revealed that the pooled incidence of VTE was 1.8% (95% CI 1.4-2.3) among pwMS. Also, there was an incidence of 0.9% (95% CI 0.4-1.4) and 1.5% (95% CI 1-2.2) for PTE and DVT, respectively in pwMS. Analysis showed MS would be significantly associated with a twofold increased risk of VTE [risk ratios (RR) = 2.12 (95% CI 1.53-2.93)]. Although MS is not typically considered a major risk factor for VTE, the meta-analysis of cohort studies shows that MS has a relative association with an increased incidence of VTE. Future research should focus on the investigation of the effects of MS and its treatments on VTE risk, and also a full range of confounding adjustments will be needed.