Stroke Accelerates the Trajectory of Age-Related Cognitive Decline
Cognitive function declines with advancing age. The brain accumulates damage at the biochemical level, but also in the form of ruptured blood vessels and microbleeds. Supporting cells become inflammatory, myelin sheathing of axons becomes damaged, the delicate balance of complex mechanisms that supports the activities and connections of neurons runs awry. Add a stroke to all of this, and the pace of decline accelerates afterwards. The reasons why this is the case are likely more complex than simply an additional burden of inflammation, and the epidemiological paper here only demonstrates the outcome, not the mechanisms.
Stroke is a leading cause of disability and dementia worldwide, with projections suggesting a continued rise in its prevalence and burden. Recent studies have shown that cognitive impairment is highly prevalent after stroke, with cognitive deficits present in over a third of stroke survivors. However, the precise impact of stroke on the trajectory of cognitive function remains unclear. Previous studies, primarily hospital-based, have been unable to account for prestroke cognitive performance, and several population-based studies examining prestroke and poststroke cognitive function reported conflicting findings, likely due to variations in study design, sample characteristics, and statistical techniques.
This study aimed to address these inconsistencies by mapping the trajectory of cognitive function after stroke relative to the cognitive trajectory without a previous stroke using harmonized data from diverse population cohorts from the Cohort Studies of Memory in an International Consortium (COSMIC). The study included 20,860 participants with a mean (standard deviation, SD) age of 72.9 (8.0) years and follow-up of 7.51 (4.2) years. Incident stroke was associated with a substantial acute decline in global cognition (-0.25 SD), the Mini-Mental State Examination, and all cognitive domains (ranging from -0.17 SD to -0.22 SD), as well as accelerated decline in global cognition (-0.038 SD per year) and all domains except memory (ranging from -0.020 to -0.055 SD per year), relative to a stroke-free cognitive trajectory. There was no significant difference in prestroke slope in stroke survivors compared with the rate of decline in individuals without stroke in all cognitive measures.
Thus in this cohort study using pooled data from 14 cohorts, incident stroke was associated with acute and accelerated long-term cognitive decline in older stroke survivors.