Cognitive impairment after stroke: clinical determinants and its associations with long-term stroke outcomes

OBJECTIVES: To identify factors that were associated with cognitive impairment 3 months after stroke, and to examine the associations of cognitive impairment with stroke outcomes up to 4 years after stroke. DESIGN: Observational study. SETTING: Population-based stroke register. PARTICIPANTS: Six hundred forty-five subjects with first-ever stroke, identified from the register. MEASUREMENTS: Subjects were assessed for cognition using the Mini-Mental State Examination (MMSE) 3 months after stroke. Cognitively impaired subjects (MMSE <24, n = 248 (38%)) were compared with cognitively intact subjects (MMSE 24-30, n = 397) in terms of demographic details, stroke risk factors, laterality of stroke, and initial poststroke impairments. Outcome data collected at 1, 3, and 4 years poststroke included disability assessed by the Barthel Index (BI) and the Frenchay Activity Index, case fatality, and institutionalization. RESULTS: Two hundred forty-eight (38%) of 645 subjects were cognitively impaired 3 months after stroke. Using multivariate analyses, cognitive impairment was associated with age of 75 and older (odds ratio (OR) = 2.5, 95% confidence interval (CI) = 1.5-4.2), ethnicity (Caribbean/African (OR = 1.9, 95% CI = 1.2-3.2) and Asian (OR = 3.4, 95% CI = 1.1-10.2), lower socioeconomic class (OR = 2.1, 95% CI = 1.3-3.3), left hemispheric lesion (OR = 1.6, 95% CI = 1.01-2.4), visual field defect (OR = 2.0, 95% CI = 1.2-3.2), and urinary incontinence (OR = 4.8, 95% CI = 3.1-7.3). Using multivariate analyses, cognitive impairment was associated with death or disability (BI <15) at 4 years after stroke (OR = 2.2, 95% CI = 1.1-4.5). In univariate analyses, it was also associated with higher institutionalization 4 years after stroke (P =.001). CONCLUSIONS: Cognitive impairment is common 3 months after stroke and is independently associated with older age, ethnicity, lower social class, left hemispheric stroke, visual field defect, and urinary incontinence. It is associated with poor long-term outcomes, including survival and disability, up to 4 years after stroke. Because physical and cognitive impairments after stroke have independent prognostic implications, measures that evaluate both functions should be used in future studies of stroke outcome and in care of stroke patients.