Multiple sclerosis increases the risk of venous thromboembolism: a nationwide cohort analysis

Objectives: The purpose of this study was to evaluate the effects of multiple sclerosis (MS) on the risk of venous thromboembolism (VTE) development.

Methods: We identified patients diagnosed with MS in Taiwan between 1998 and 2010 using the National Health Insurance Research Database and the Catastrophic Illness Patient Database (RCIPD). Each MS patient was frequency matched to 4 controls according to age, sex and the year of MS registration to the RCIPD. Patients with a history of VTE and incomplete information of age and sex were excluded. All patients were followed up from the index year until VTE diagnosis, loss to follow-up or the end of 2010. We calculated the hazard ratios (HRs) and 95% confidence intervals (CIs) of VTE in the MS and comparison cohorts using Cox proportional hazards regression models.

Results: We followed up 1238 MS patients and 4952 comparison patients for approximately 6437 and 27 595 person-years, respectively. After adjusting for age, sex and comorbidities, the MS patients exhibited a 6·87-fold increased risk of VTE compared with the control patients. Women with MS were associated with an 11·1-fold increased risk of VTE development compared with the non-MS women (95% CI: 2·70-45·5). The MS patients aged < 50 years exhibited a 14·8-fold increased risk of developing VTE compared with age-matched patients in the comparison cohort (95% CI: 2·99-73·4). The risk of VTE development increased with the duration of hospitalization stay.

Conclusion: MS patients are associated with significantly greater risk of developing VTE compared with non-MS patients.