Hypertension and Cognitive Functioning

Abstract

O ur objective is to characterize the development of the literature on hypertension and cognitive functioning from a historical perspective. This goal was stimulated by the review on "Historical Trends and Milestones in Hypertension Research" in the October 2012 issue of Hypertension.1 Our specific aims are threefold: (1) to trace and describe the history of this area of research; (2) to identify milestones in knowledge and methods; and (3) to discuss briefly how this literature translates into patient care. The topic is of major relevance to research and practice because hypertension is a well-known risk factor for decline in cognitive performance within the normal range of cognitive functioning, mild cognitive impairment (MCI) and dementia. It is important to emphasize 3 features of the review: (1) it is not designed as a critical review of the literature, but rather to describe the historical influences on our current knowledge base (poor, mediocre and outstanding papers from the past have all shaped our present); (2) word-count limitations require that we omit statistical detail except to emphasize effect sizes in pivotal papers; and (3) each milestone topic is addressed by noting the earliest work then followed by examples of papers representing pivotal events. A number of comprehensive reviews of this literature are available, 2-6 including a seminal paper summarizing the formative years of this research.7 Please see http://hyper.ahajournals.org for citations to additional reviews of the literature and papers published in Hypertension. We recognize the importance of the emerging literature on hypotension and cognitive function, but refer the readers to previous reviews which include this topic. 8-10 Measurement of Cognitive FunctioningIn this paper, the term cognitive performance is used to describe the outcome of studies measuring a full range of ability from low to high. The term cognitive functioning is used to describe, more generally, findings with respect to cognitive performance, MCI, or dementia. Cognitive deficit is used in a comparative sense, hypertensive individuals compared to some other group of subjects. The term impairment is used to indicate clinically significant cognitive dysfunction. Lezak et al11 provide a compendium of over 700 psychometric tests and subtests. They describe behaviors required to perform the test, the latent abilities that the tests purport to measure, eg, working memory, attention, and executive functioning. Classic neuropsychological texts describe how tests and the latent cognitive constructs they measure are used to make inferences about the hemisphere, locus, and extent of brain injury.12 Figure 1 shows an example of a hypothetical study in which tests are being used to explore the hypothesis that hypertension is more strongly associated with executive functioning 13 and that this phenomenon is associated with reduced cerebral blood flow (CBF) to the frontal and prefrontal brain areas, but not to other brain areas.14 Executive functioning (EF) can be defined as t...

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