Hypertension and cognitive functioning among the elderly: an overview.

This paper reviews the longitudinal studies in which the association between hypertension and cognitive functioning has been explored. The findings of these studies are far from being consistent: positive, adverse, or no relationships between cognitive performance and blood pressure have been reported. In some studies, cognitive functioning was related only to systolic blood pressure, whereas in others, it was related to diastolic blood pressure alone. Most probably, the inconsistency is due to the variability in research design, the measures employed, and data management. Some of the main methodological issues are the wide range in the age of the subjects and the variability in hypertension at baseline. Length of exposure to hypertension was rarely considered, and the search for the possible effects of the different antihypertensive treatments on cognitive ability is in its infancy. Many studies seek to identify cognitively impaired elderly and do not distinguish between the different types of dementia or the different cognitive domains. Thus, the possibility that hypertension affects specific cognitive functions has not been explored. The use of subdivisions of blood pressure values may have obscured nonlinear relationship. Nevertheless, the pattern that emerges is that midlife hypertension enhances cognitive impairment later in life, but at old age, mild hypertension may increase cognitive performance. Directions for future research to further elucidate the complex relationship between age, blood pressure, and cognition are discussed.