COGNITIVE IMPAIRMENT AND RISK OF STROKE IN THE OLDER POPULATION

To the Editor: We read with interest the article of Dr. Ferrucci and colleagues1 reporting that cognitive impairment, as evidenced by a low score on a mental status questionnaire, was an independent risk factor for incident stroke in an older population. The authors suggested that silent cerebrovascular disease may be an important contributing factor to cognitive impairment and stroke occurrence in older clinically stroke-free persons. We would like to offer our own observations supporting the proposed relationship between cognitive impairment and stroke risk. We examined 242 patients 60 years of age or older consecutively hospitalized with acute ischemic stroke who had survived the first 3 months without recurrence, and we followed them prospectively to investigate risk factors for long-term stroke recurrence. Among many variables, we examined dementia status, which was determined 3 months after stroke onset using modified DSM-III-R criteria based on neuropsychological and functional assessments, as a risk factor for recurrent stroke. We found that dementia was a significant independent predictor of stroke recurrence (RR = 2.71, 95% CI = 1.15 to 4.12) after adjusting for demographic characteristics and conventional stroke risk factors.2 Previous studies have found that stroke itself significantly increases the immediate and long-term risk of dementia,3, 4 whereas our study suggests that dementia after stroke in older stroke populations confers a significantly increased risk of recurrent cerebrovascular events. Taken in aggregate, these findings suggest a complex relationship between cognitive impairment and stroke risk such that one may lead to the other in a bidirectional sequence of events. Further prospective epidemiological studies are needed to elucidate the pathogenic mechanisms by which cognitive impairment leads to an increased stroke risk in persons with and without a history of clinically evident stroke. As suggested by Ferrucci and colleagues,1 for example, cognitive impairment may be an early manifestation of silent cerebrovascular disease in older adults. A better understanding of these pathogenic mechanisms could lead to targeted interventions to help reduce the significant public health burden of stroke and dementia in the older population.