Preexisting dementia in stroke patients. Baseline frequency, associated factors, and outcome

BACKGROUND AND PURPOSE: The link between stroke and degenerative dementia, especially Alzheimer's disease, is closer than expected by chance. Dementia after stroke may be due to the cumulative effect of vascular and degenerative changes. The prevalence of dementia just before stroke onset remains unsettled. The aim of this study was to determine the frequency of preexisting dementia in stroke patients, associated factors, and consequences on outcome. METHODS: We evaluated the cognitive functioning prior to stroke in 202 consecutive patients with ischemic or hemorrhagic stroke by means of the Informant Questionnaire on Cognitive Decline in the Elderly (IQCODE). We classified in the dementia group patients with IQCODE scores of 104 or more. Six months after stroke onset, survivors underwent a battery of neuropsychological tests. RESULTS: Thirty-three patients were demented before stroke (16.3%; 95% confidence interval, 11.2 to 21.4). There was no diagnosis of dementia in 32 of these 33 patients. We determined by logistic regression analysis that female sex, family dementia, leukoaraiosis, and cerebral atrophy are independently associated with prestroke dementia. All survivors who had IQCODE scores of 104 or more at the acute stage met criteria for dementia 6 months later. CONCLUSIONS: Our study showed that one sixth of stroke patients have preexisting dementia. Therefore, some patients with so-called "poststroke dementia" probably had unrecognized preexisting dementia.