A systematic review of reviews to examine the association between hypertension and cognitive impairments in adults

Abstract

Background: Essential hypertension is thought to be a risk factor for cognitive impairment. Researchers have proposed several explanations for this link, including endothelial dysfunction/vascular dysregulation, white matter disease, the renin-angiotensin system and inhibition of acetylcholine release by angiotensin II, strategic strokes or tissue loss with strokes, or abnormal insulin signaling. We conducted a review of reviews to investigate the clinical evidence for an association between hypertension and cognitive impairment in adults. Methods: We included any English-language systematic review or meta-analysis that reported on primary studies conducted in humans aged 18 years or older. The primary studies had to be randomized controlled trials or observational studies with comparison groups. We searched MEDLINE, EMBASE, and PsycINFO from January 1, 2010 to May 23, 2014 to obtain the reviews. We assessed the methodological quality of the included reviews using the A M ea S urement T ool to A ssess Systematic R eviews (AMSTAR) tool. Results: We included four meta-analyses and one systematic review. Results suggested small associations between hypertension and global cognition, episodic memory, and attention, but no associations between hypertension and language, executive function, information processing speed, and visuoperceptual skills. Results indicated no association between hypertension and Alzheimer’s disease, but a positive association between hypertension and vascular dementia. The overall methodological quality of the included reviews was moderate. Caution is required when interpreting the meta-analyses because the quantitative results were synthesized across different definitions of hypertension and different neuropsychological tests. Conclusions: Further work is required to understand the association between hypertension and cognitive impairment from a clinical perspective.