To Örebro University

Introduction: A raised risk for several comorbid diseases among MS patients has been identified. Most previous studies examined diseases separately rather than considering the overall burden of comorbidity. Multiple comorbidities may have important implica-tions for clinicians managing MS patients.

Aims: To describe the lifetime burden of comorbid diseases among MS patients and the rate of these diseases compared with the general population in Sweden.

Methods: MS patients identified using the MS Register and the Patient Register (PR) between 1964-2012 (n=25476) were matched by sex, age and county of residence with up to 10 general population comparators (n=251170). Prevalent and incident diag-noses of diseases other than MS for seven diseases categories were identified using the PR between 1987-2012. The total num-ber of comorbid diseases were compared using chi-square tests and prevalence rate ratios (PRR) were calculated. Hazard ratios (HR) were estimated using Cox regression and flexible non-para-metric survival models with age as the underlying time scale, MS as exposure, an additional comorbid disease as the outcome, adjusted for matching variables, education, number of previous comorbid diseases, and duration since study entry.

Results: The proportion of MS patients with 1,2 or 3+ comorbid disease diagnoses was greater than in the comparison cohort across all age groups (p< 0.001). The largest PRR (range 1.22-9.99) were among younger age groups (6-18,19-40,41-60 years) in autoim-mune, cardiovascular, diabetes and seizure disease categories. Additionally, PRR were elevated in depression and respiratory dis-eases, but not for renal diseases. PRR between 61-80 and 81-100 years were reduced compared to younger groups across all comorbid diseases, but remained elevated for respiratory, seizure and renal dis-eases. The adjusted HR for an additional diagnosis in MS patients was 1.7 (95% CI 1.66-1.75). Flexible modelling showed signifi-cantly higher risk for all ages of an additional disease diagnosis in MS patients; twice the risk (95% CI 1.8-2.2) up to age 35 years and decreasing with age to 1.3 (95% CI 1.5-1.25) over age 80 years.

Conclusions: MS patients in Sweden experience an increased burden of comorbidity and tend to be diagnosed with these dis-eases at an earlier age than the general population. This increased disease burden demonstrates the clinical reality of treating MS, indicating the need for integrated treatment approaches over sev-eral medical specialties.