Infections in patients with multiple sclerosis : a nationwide cohort study in Sweden

• Introduction: Previous studies suggest that susceptibility to infections is not raised among multiple sclerosis (MS) patients in general, but certain specific infections, such as those of the urinary or respiratory tract, are more common in patients with higher disability. However, contemporary MS cohorts to a higher degree are treated with newer disease-modifying treatments (DMTs) that exert stronger effects on the immune defence. Here we investigated the rate of infections in patients before and after MS diagnosis as compared with a matched MS-free population.Methods: Incident MS patients diagnosed in 2008-2016 were identified in the Swedish National Patient Register. MS patients were matched to 10 MS-free individuals by age, sex, and region of residence. Incidence rates per 10,000 person-years and incidence rate ratios (IRRs) of first infection by site and type were calculated after the MS diagnosis date.Results: In total, 6,602 MS patients were identified and compared with 61,828 without MS (female, 69%; median age, 40 years). During the year before MS diagnosis, MS patients showed higher proportions of urinary and kidney infections, meningitis and encephalitis, and bacterial infections compared with the MS-free cohort.After MS diagnosis, an increased risk of non-serious (IRR 1.65; 95% CI 1.56-1.75) and serious (admitted to hospital) infections (IRR 2.59; 95% CI 2.33-2.89) was detected among MS patients relative to the MS-free cohort. The risk of some bacterial (IRR 2.23; 95% CI 1.98-2.52) and some viral infections (IRR 1.70; 95% CI 1.48-1.96) was higher in MS patients of both sexes while only males showed an increased risk of fungal infections (IRR 1.91; 95% CI 1.26-2.89). Relative to the MS-free cohort, MS patients had an increased risk of all infection types, such as meningitis and encephalitis (IRR 6.16; 95% CI 4.47-8.48), other opportunistic infections (IRR 2.72; 95% CI 2.08-3.55), urinary and kidney infections (IRR 2.44; 95% CI 2.24-2.66), herpes virus (IRR 2.32; 95% CI 1.77-3.05), pneumonia and influenza (IRR 1.92; 95% CI 1.66-2.23), and skin infections (IRR 1.89; 95% CI 1.65-2.16).Conclusions: After MS diagnosis, patients had higher incidences of non-serious and serious infections compared with a cohort without MS. MS patients had an increased risk of being diagnosed during follow-up with most infection types compared with controls. This risk was particularly high for meningitis and encephalitis.

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MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Neurologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Neurology (hsv//eng)

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