The effects of aging and disease duration on cognition in multiple sclerosis

Objectives: Multiple sclerosis (MS) is a disease of the central nervous system that can interfere with cognitive functions. The purpose of this study is to document the impact of MS, aging and disease duration on cognitive functioning as both life expectancy and incidence of the disease among persons with MS (PwMS) aged 50 years and over (late-onset MS) are increasing in the last two decades. Methods: Exhaustive neuropsychological evaluation was performed in 84 PwMS (30 young, 30 elderly adult onset, 25 elderly late-onset) and 50 control participants (25 young, 24 elderly). ANCOVAs and hierarchical linear regressions were used to meet the objectives. Results: Interaction effects were found between age and presence of MS on higher executive function and information processing speed/working memory. After controlling for confounding variables (fatigue, quality of life, depression, MS course, comorbidity), results demonstrated an important role of age on all cognitive functions but only a trend of disease duration on information processing speed/working memory. Conclusion: Decline in higher executive functions and information processing speed/working memory in aging is accentuated by the presence of MS, but the impact of age and MS on memory are independent. Age appears to be the variable having the most important role on cognition.