Clinical course of multiple sclerosis and labour-force absenteeism: a longitudinal population-based study

Multiple sclerosis (MS) is a chronic neurological disease associated with substantial disability and morbidity. The objective of our study was to assess the long-term consequences of MS clinical course on sick leave and disability pension.

Patients with relapsing-remitting MS (RRMS), secondary progressive MS (SPMS) and primary progressive MS (PPMS) were identified through the Swedish Multiple Sclerosis Registry. We calculated the mean annual prevalence and number of sick leave and disability pension days by clinical course, age and year pre- and post-diagnosis, and compared outcomes using Welch's t-tests and ANOVA models, mixed-effects regression and survival analysis.

The sample included 5371 patients (4568 with RRMS, 390 with SPMS and 413 with PPMS). The mean annual number of days with sick leave and disability pension ranged from 101 at 1 year after diagnosis to 164 after 11 years for patients with RRMS. Corresponding estimates for PPMS were 188 and 311 days. Higher levels of absenteeism were observed in patients with PPMS versus RRMS 7 years before diagnosis for sick leave (P < 0.025) and 10 years before diagnosis for disability pension (P < 0.034). Differences between SPMS and PPMS were minor.

Patients with RRMS had substantially lower levels of sick leave and disability pension over time compared with their counterparts with SPMS and PPMS, whereas labour-force absenteeism was similar for patients with SPMS and PPMS. These findings contribute to the understanding of the impact of MS on socioeconomic outcomes and help inform the discussion on the clinical classification of different courses of the disease.