Risk of Multiple Sclerosis in People Living with HIV: An International Cohort Study

Objective: There has been interest in a possible negative association between HIV and multiple sclerosis (MS). We aimed to compare the risk of MS in a cohort of individuals living with HIV to that in the general population. Methods: Population-based health data were accessed for 2 cohorts of HIV-positive persons from Sweden and British Columbia, Canada. Incident MS was identified using MS registries or a validated algorithm applied to administrative data. Individuals with HIV were followed from 1 year after the first clinical evidence of HIV or the first date of complete administrative health data (Canada = April 1, 1992 and Sweden = January 1, 2001) until the earliest of incident MS, emigration, death, or study end (Canada = March 31, 2020 and Sweden = December 31, 2018). The observed MS incidence rate in the HIV-positive cohort was compared to the expected age-, sex-, calendar year-, income-specific, and region of birth-specific rates in a randomly selected sample of >20% of each general population. The standardized incidence ratio (SIR) for MS following the first antiretroviral therapy exposure ("ART-exposed") was also calculated. Results: The combined Sweden-Canada cohort included 29,163 (75% men) HIV-positive persons. During 242,248 person-years of follow-up, 14 incident MS cases were observed in the HIV-positive cohort, whereas 26.19 cases were expected. The SIR for MS in the HIV-positive population was 0.53 (95% confidence interval [CI] = 0.32-0.90). The SIR for MS following the first ART exposure was 0.55 (95% CI = 0.31-0.96). Interpretation: This international population-based study demonstrated a lower risk of MS among HIV-positive individuals, and HIV-positive ART-exposed individuals. These findings provide support for further exploration into the relationship among HIV, ART, and MS. ANN NEUROL 2023