Cognitive reserve impacts on disability and cognitive deficits in acute stroke.

OBJECTIVE: Although post-stroke cognitive deficit can significantly limit patient independence and social re-integration, clinical routine predictors for this condition are lacking. 'Cognitive reserve' limits the detrimental effects of slowly developing neurodegeneration. We aimed to determine whether comparable effects also exist in acute stroke. Using 'years of education' as a proxy, we investigated whether cognitive reserve beneficially influences cognitive performance and disability after stroke, whilst controlling for age and lesion size as measure of stroke pathology.

METHODS: Within the first week of ischemic right hemisphere stroke, 36 patients were assessed for alertness, working memory, executive functions, spatial neglect, global cognition and motor deficit at 4.9 ± 2.1 days post-stroke, in addition to routine clinical tests (NIH Stroke Scale, modified Rankin Scale on admission < 24 h post-stroke and at discharge 9.5 ± 4.7 days post-stroke). The impact of education was assessed using partial correlation analysis adjusted for lesion size, age, and the time interval between stroke and assessment. To validate our results, we compared groups with similar age and lesion load, but different education levels.

RESULTS: In the acute stroke phase, years of education predicted both severity of education independent (alertness) and education dependent (working memory, executive functions, global cognition) cognitive deficits and disability (modified Rankin Scale). Spatial neglect seemed to be independent.

INTERPRETATION: Proxies of cognitive reserve should be considered in stroke research as early as in the acute stroke phase. Cognitive reserve contributes to inter-individual variability in the initial severity of cognitive deficits and disability in acute stroke, and may suggest individualised rehabilitation strategies.