Poststroke Dementia among Older Adults
Stroke and dementia are major health problems affecting older people. Cerebrovascular disease is the second-leading cause of dementia after Alzheimer’s disease, the third- leading cause of death, and one of 10 leading causes of physical disability. In parallel with the increased prevalence of stroke in aging populations and the decline in mortality from stroke, the rate of diagnosed poststroke dementia has increased, causing a growing financial burden for health care systems. This article discusses the epidemiology, etiology, and determinants of poststroke dementia and outlines the search for a suitable treatment.
Key words: dementia, stroke, cognition, risk factors, cognitive impairment.
Introduction
Stroke and dementia are major health problems affecting older people. Cerebrovascular disease is the second leading cause of dementia after Alzheimer’s disease (AD), the third leading cause of death, and one of 10 leading causes of physical disability.1 In parallel with the increased prevalence of stroke in aging populations and the decline in mortality from stroke, the rate of diagnosed poststroke dementia (PSD) has increased, causing a growing financial burden for health care systems.
Dementia occurring after a stroke is PSD irrespective of its possible cause: vascular, degenerative, or mixed. Vascular dementia (VaD), a direct consequence of ischemic or hemorrhagic stroke, is not a synonym for PSD but is one of its possible causes.
Epidemiology
The prevalence of dementia in population-based studies is about 30% among persons with history of stroke: this is 3.5-5.8 times higher than among those without stroke.2,3 In hospital-based studies, the prevalence of PSD ranges from 6 to 31.8%. So there is a great discrepancy in the data, which is a consequence of different methodologies of published studies. The biggest impact on PSD prevalence has been the choice of diagnostic criteria for dementia. Rasqiun et al.4 showed that in one stroke population the prevalence of PSD 1 month after a stroke varied depending upon the diagnostic criteria for dementia that was used, ranging from 11.3% using criteria from the National Institute of Neurological Disorders and Stroke and Association Internationale pour la Recherché et l’Enseignement en Neurosciences (NINDS-AIREN) to 15.5% using criteria from Diagnostic and Statistical Manual of Mental Disorders, Revised Third Edition (DSM-III-R), 16% using criteria from Alzheimer’s Disease Diagnostic and Treatment Centers (ADDTC), 18.0% using criteria from DSM-IV, 19.6% with DSM-III, and 20.1% using criteria from the International Classification of Diseases, 10th Revision: Neurological Adaptation (ICD-10 NA).
Another factor affecting PSD prevalence is the time from onset of stroke to neuropsychological evaluation. According to published data, 5.9-31.8% of individuals have dementia 3 months after stroke,5,6 8.5-22.8% 6 months after stroke.7,8 10-21.4% 1 year after stroke,7,8 and 21.6%8 and 19.2%8 2 and 3 years after stroke, respectively.
The prevalence of PSD is also affected by a lack of homogeneity of studied populations (e.g., variety in ethnicity, age range, exclusion or inclusion of patients with aphasia, presence of prestroke dementia, or impairment too severe to allow for neuropsychological evaluation after stroke). Evaluating prestroke dementia is very important in the proper estimation of PSD prevalence: according to different studies, 9.2-16.3% of patients admitted to hospital with stroke already have prestroke dementia,9,10 usually unrecognized previously. The inclusion of individuals with prestroke dementia can increase the frequencies of PSD. On the other hand, the exclusion of patients too severely impaired to undergo neuropsychological examination or patients with aphasia can artificially decrease the prevalence of PSD.
In population-based studies examining the incidence of PSD