Previous and incident dementia as risk factors for mortality in stroke patients

We sought to determine whether previous or incident dementia increases the risk of mortality after stroke. We assessed clinical, functional, and cognitive status in 324 consecutive stroke patients who were followed up for 24 months. Prestroke dementia was diagnosed at admission (Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition criteria) and poststroke dementia 3 months after stroke (Diagnostic and Statistical Manual of Mental Disorders, Fourth Edition criteria). The proportion of patients surviving in the groups with and without dementia and the relative risk of mortality were calculated with Kaplan-Meier and with Cox proportional hazards analyses, respectively, for prestroke, stroke-related, and poststroke dementia. Forty-nine patients (15.1% of the total sample) were found to have prestroke dementia. Three months after stroke, 75 cases had poststroke dementia: 50 incident cases (20% of 251 reexamined cases) with stroke-related dementia and 25 already demented before the stroke. After a mean follow-up of 16.1+/-9.9 months, the proportion of survivors was 20.4% in patients with and 72.6% in those without prestroke dementia. After a mean follow-up of 22.1+/-6.7 months, the proportion of survivors was 58.3% in patients with and 95.4% in those without stroke-related dementia. Using multivariate analysis and adjusting for age, sex, hypertension, diabetes, previous stroke, heart disease, and severity and recurrence of stroke, we found the relative risk of mortality associated with prestroke dementia to be 2.1 (95% CI, 1.2 to 3.6), with stroke-related dementia 6.3 (95% CI, 2.3 to 17.3), and with poststroke dementia 8.5 (95% CI, 3.4 to 20.9). Both previous dementia and incident dementia adversely influence long-term survival after stroke, even after adjustment for other predictors of stroke mortality.