Trajectories of cognitive decline after incident stroke – a COSMIC collaboration study

Abstract

Introduction: Poststroke cognitive impairment is common, but the trajectory and magnitude of cognitive change after stroke are unclear. We aimed to measure changes in the trajectory of cognitive function following a first stroke, controlling for pre-stroke cognitive performance using diverse population-based studies from the Cohort Studies of Memory in an International Consortium (COSMIC). Methods: Fourteen longitudinal cohorts from 11 countries from Asia, Africa, North America, South America, Europe, and Australia contributed data. Cognitive domain scores were formed by selecting the most common test administered amongst studies in each domain (memory, processing speed, language, and executive function) and the scores standardised; global cognition was the standardised average of the 4 domains and the primary outcome. One-stage IPD meta- analysis with linear mixed model and regression discontinuity design was used to model the change in cognitive function. Time-dependent incident stroke, age, time in study, and time since stroke were included in the basic model. In the full model we adjusted for sex, education, ethno- racial group, study period and potential confounders significant in the basic model at p<0.1, which were history of diabetes, hypertension, cardiovascular disease, depression, smoking, alcohol use, and APOE ε4 carrier. Results: The studies contributed data on 20,980 participants (mean age, 72.9 years; SD=8.0; 43% male), with 17,079 (81%) having follow-up data. The mean follow-up time was 7.54 years (SD=4.15) and 4.9% (n=1,031) had a first incident stroke during follow-up. Stroke was associated with acute decline in global cognition (-0.31 SD; 95% CI: -0.38 to -0.23) and accelerated rate of decline (-0.058 SD/year, 95% CI: -0.072 to -0.043, compared to the rate of cognitive change before stroke) after covariate adjustments. For those who had a first incident stroke, their rate of cognitive decline before stroke was not significantly different from the rate of decline in those who did not experience a stroke over follow up. Discussion: Incident stroke was associated with acute decline in cognitive function and accelerated long-term cognitive decline.