Background: Clinical studies suggest that disease course of multiple sclerosis (MS) differs according to age of onset. However, most of these studies were cross-sectional and had modest sample sizes. Population-based administrative data provide an alternative long-term perspective on disease progression and further document the association between age at diagnosis and progression of MS. Our objective was to study the association between age at diagnosis and the use of health services for MS.
Methods: Data on 1426 subjects with MS were extracted from the Québec Birth Cohort on Immunity and Health, which includes 400,611 individuals born in Québec between 1970 and 1974, followed until 2014 using administrative databases. Subjects who had ≥3 hospital or physician claims for MS during the follow-up were classified as having MS using an algorithm validated previously. Four indicators of health services use for MS were considered: number of visits to a neurologist, number of visits to a general practitioner (GP), number of visits in an emergency room and number of days of hospitalization. Generalized additive models, with a quasi-Poisson distribution were used to estimate the association between age at diagnosis and the rates of health services. Models were adjusted for the duration of follow-up, the proportion of women and the proportion of individuals who are materially and socially disadvantaged.
Results: Most subjects (76%) were women and 29% of them were between 21 and 29 years old at MS diagnosis. Subjects who were diagnosed with MS before age 29 years had a higher rate of visits to a neurologist, a higher rate of hospitalization and a lower rate of visits to a GP in the first year following MS diagnosis compared to those who were diagnosed at age 29 years or later. There were not many differences observed between subjects who had MS diagnosis before 29 years and those who had MS diagnosis at least at 29 years in the other periods of follow-up for all the indicators of health services.
Conclusion: Although we observed some changes in the rates of visits to a neurologist and to a GP between the two diagnostic age groups, we could not conclude that age at diagnosis influences the rate of health services for MS. The use of health services allowed us to describe the association between age at diagnosis and the progression of MS at the population level.
Keywords: Age at diagnosis; Health services; Multiple sclerosis; Québec.
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