Is age an aggravating factor of cognitive impairment in multiple sclerosis (MS)?

Résumé En

If cognitive disorders in MS are now well documented, few studies examined the impact of age on cognitive impairment. This study investigates the potentially differential impact of age on cognition in MS patients compared to matched healthy participants and according to the clinical form of the disease. 321 MS-patients (192 relapsing-remitting, 99 secondary-progressive, 30 primary-progressive), matched to 258 controls, underwent cognitive assessment: episodic memory (Selective Reminding Test), working memory (forward and backward digit spans), processing speed (code), cognitive flexibility (categorical and phonemic fluencies). Moderation analyses via hierarchical linear regressions tested the moderating effects of group on the relationship between age and cognition (with education level as a co-variate). For all cognitive variables, age and MS negatively predicted cognitive performances. No interaction effects between age and group (MS vs controls) were observed on all cognitive variables. Regarding the effect of clinical form (relapsing-remitting vs. progressive), the progressive form negatively impacted processing speed and cognitive flexibility. However, no interaction effects were observed between age and clinical form of MS. While age had a negative impact on cognitive functioning, no differential effect of age was observed, either between patients and healthy participants or among the different clinical forms of the disease. MS represents a risk factor for the occurrence of cognitive impairment. Nevertheless, age does not seem to be an aggravating factor on the importance of this impairment.