Risk factors for incident dementia after stroke. Role of hypoxic and ischemic disorders

Stroke significantly increases the risk of dementia in the elderly, yet the risk factors for incident dementia after ischemic stroke are not well understood. We attempted to determine whether hypoxic-ischemic (HI) disorders, which may result from comorbid medical conditions (eg. seizures, cardiac arrhythmias, pneumonia), would be an independent risk factor for the development of new dementia after stroke.

We prospectively followed 185 initially nondemented patients with ischemic stroke (age, 70.3 +/- 7.7 years) for a maximum of 52.8 months. We diagnosed the presence of dementia at annual examinations based on neuropsychological testing and modified DSM-III-R criteria. HI disorders were identified by record review or examination during hospitalization. We used Kaplan-Meier analysis to determine the cumulative proportion of patients with and without HI disorders who survived free of dementia and used Cox models to estimate the relative risk of dementia associated with HI disorders.

The cumulative proportion (+/- SE) surviving without dementia was 51.7 +/- 10.9% in the HI group versus 78.2 +/- 4.3% in the non-HI group after 52.8 months of observation. The relative risk of incident dementia associated with HI events was 4.3 (95% confidence interval = 1.9 to 9.6) after we adjusted for demographic factors, recurrent stroke, and baseline cognitive function.

We conclude that HI disorders may be a significant independent risk factor for incident dementia after stroke, even after adjustment for other recognized predictors of cognitive decline. Recognition of HI cerebral damage as a possible pathogenic mechanism for dementia after stroke may allow targeted therapeutic interventions to prevent subsequent cognitive deterioration.