VAS-COG: Mild Cognitive Impairment May Increase Stroke Risk

SAN ANTONIO, July 13 -- Mild impairment of the executive function domain of cognition may represent an early marker of increased stroke risk, according to data from the Framingham Study.

Mildly impaired executive function conferred a stroke hazard ratio of 2.4 compared with normal executive function in the original Framingham cohort, Sudhas Seshadri, M.D., of Boston University reported at the International Society of Vascular Behavioral and Cognitive Disorders meeting here.

An even greater effect was seen in the Framingham Offspring cohort, as mildly impaired executive function increased the relative risk of stroke almost five-fold, the investigators added

Mild impairment in the verbal memory or amnestic domain of cognitive function was associated with an increased risk of dementia and Alzheimer's disease in the original Framingham cohort but not stroke.

"We know that vascular risk factors increase the risk of stroke and independently increase the risk of impaired cognitive function in people who have not had a stroke," said Dr. Seshadri. "It could be that poorer cognitive function is a marker of the duration or severity of exposure to vascular risk factors. It might also be a marker of susceptibility to these risk factors."

The study consisted of 1,312 original Framingham participants who underwent cognitive testing during 1976 to 1978 and 1,941 Framingham Offspring participants who had cognitive evaluations during 1998 to 2004. All participants were free of stroke and dementia at baseline, and the offspring participants also were known to be free of such neurologic conditions.

Neuropsychological assessment of the study participants comprised five domains of cognition, but Dr. Seshadri and colleagues looked for mild cognitive impairment in two domains-- verbal memory and executive function. They defined mild impairment as 1.5 standard deviations below adjusted means scores for the population.

Multivariate proportional hazards models were used to estimate the 10-year risk of incident stroke for participants with mild impairment in either of the two domains.

During 10 years of follow-up, 92 strokes and 84 cases of dementia occurred in the original Framingham cohort. In the younger offspring cohort, 25 strokes occurred, and dementia occurred too infrequently to assess.

In the original cohort, mild impairment in executive function independently predicted stroke risk (P<0.05) but not dementia or Alzheimer's disease. Mild impairment in verbal memory as associated with almost a six-fold increase in the relative risk of dementia or Alzheimer's disease (P<0.001), but did not predict stroke risk.

In the offspring cohort mildly impaired executive function with a stroke hazard ratio of 4.8 (P<0.001). Impaired verbal memory did not predict stroke risk.

Cognitive function was assessed by means of simple, office-based tests that could easily be incorporated into stroke risk assessment, Dr. Seshadri said.