Dementia three months after stroke. Baseline frequency and effect of different definitions of dementia in the Helsinki Stroke Aging Memory Study (SAM) cohort.

BACKGROUND AND PURPOSE

Vascular dementia is a common cause of dementia, and cerebrovascular disease is related to a higher risk of dementia. The frequency of dementia associated with ischemic stroke and the effects of different definitions of dementia in the diagnosis are still incompletely known. We evaluated the frequency of cognitive decline and dementia 3 months after ischemic stroke in a large stroke cohort.

METHODS

Our cohort consisted of consecutively admitted ischemic stroke patients (n = 486) aged 55 to 85 years in the Helsinki (Finland) Stroke Aging Memory Study (SAM). Subjects were assessed by structured medical, neurological, and radiological examinations and interview with a close informant, as well as by the Mini-Mental State Examination and detailed clinical mental status examination of defined cognitive domains. The criteria for dementia were those of the Diagnostic and Statistical Manual of Mental Disorders (DSM) (DSM-III, DSM-III-R, and DSM-IV), the National Institute of Neurological Disorders and Stroke-Association Internationale pour la Recherche et l'Enseignement en Neurosciences (NINDS-AIREN), and the International Classification of Diseases, 10th Revision (ICD-10).

RESULTS

We found that 451 (92.8%) of the patients were testable, 239 (49.2%) of the patients were women, and the mean age was 71.2 years. Any cognitive decline was present in 61.7%. In the groups aged 55 to 64, 65 to 74, and 75 to 85 years, the frequency of any cognitive decline was 45.7%, 53.8%, and 74.1% (P = .0008), respectively. The frequency of dementia was 25.5% by DSM-III, 20.0% by DSM-III-R, 18.4% by DSM-IV, 21.1% by NINDS-AIREN, and 6.0% by ICD-10 criteria. The frequency increased with increasing age: by the DSM-III definition, frequency in the aforementioned age groups was 19.3%, 23.7%, and 25.5%, respectively (P = .014). There was an overlap in the cases diagnosed as demented according to the different guidelines. Compared with standard diagnosis, the DSM-III was the most sensitive and ICD-10 the most specific. Concordance was moderate between the DSM criteria and NINDS-AIREN criteria but was poor between ICD-10 and the other criteria.

CONCLUSIONS

Cognitive decline and dementia were frequent in the cohort of ischemic stroke patients, and the frequency increased with increasing age. Different definitions gave different frequency estimates, and overlap in the cases was observed. Our findings question the validity of current criteria for dementia in the setting of cerebrovascular disease and emphasize the need for further debate and studies to refine the categories of cognitive impairment related to cerebrovascular disease.