Trajectories of disposable income among people of working ages diagnosed with multiple sclerosis: a nationwide register-based cohort study in Sweden 7 years before to 4 years after diagnosis with a population-based reference group.

Objectives: To describe how disposable income (DI) and three main components changed, and analyse whether DI development differed from working-aged people with multiple sclerosis (MS) to a reference group from 7 years before to 4 years after diagnosis in Sweden.

Design: Population-based cohort study, 12-year follow-up (7 years before to 4 years after diagnosis). Setting: Swedish working-age population with microdata linked from two nationwide registers. Participants: Residents diagnosed with MS in 2009 aged 25-59 years (n=785), and references without MS (n=7847) randomly selected with stratified matching (sex, age, education and country of birth). Primary and secondary outcome measures: DI was defined as the annual after tax sum of incomes (earnings and benefits) to measure individual economic welfare. Three main components of DI were analysed as annual sums: earnings, sickness absence benefits and disability pension benefits.

Results: We found no differences in mean annual DI between people with and without MS by independent t-tests (p values between 0.15 and 0.96). Differences were found for all studied components of DI from diagnosis year by independent t-tests, for example, in the final study year (2013): earnings (-64 867 Swedish Krona (SEK); 95% CI-79 203 to -50 528); sickness absence benefits (13 330 SEK; 95% CI 10 042 to 16 500); and disability pension benefits (21 360 SEK; 95% CI 17 380 to 25 350). A generalised estimating equation evaluated DI trajectory development between people with and without MS to find both trajectories developed in parallel, both before (-4039 SEK; 95% CI -10 536 to 2458) and after (-781 SEK; 95% CI -6988 to 5360) diagnosis.

Conclusions: The key finding of parallel DI trajectory development between working-aged MS and references suggests minimal economic impact within the first 4 years of diagnosis. The Swedish welfare system was responsive to the observed reductions in earnings around MS diagnosis through balancing DI with morbidity-related benefits. Future decreases in economic welfare may be experienced as the disease progresses, although thorough investigation with future studies of modern cohorts are required.