Blood pressure, antihypertensive treatment and cognitive decline in older adults

Abstract

Hypertension is prevalent in older adults and associated with impaired cognitive function compared to normotensive peers. The effect of antihypertensive therapy on preventing or reducing the rate of cognitive decline is unclear. The studies in this thesis examined the association of elevated blood pressure in older adults on changes in specific cognitive domains and tested the hypothesis that antihypertensive treatment reduces the rate of cognitive decline in older adults with mild hypertension. 507 older individuals (70-89 years) were recruited from a general practice population (250 normotensives, and 257 hypertensives who participated in an international, placebo- controlled trial of candesartan). Cognition was assessed annually for 3-5 years using a comprehensive computerised assessment battery and tests of executive function. Analysis of cognitive function at baseline showed hypertensive subjects performed worse than normotensives across a range of tasks (Chapter 3). Exploratory factor analyses were conducted on the baseline data to derive composite scores used to characterise five domains of cognition and reduce the number of statistical comparisons (Chapter 4). Regression analyses were performed for each participant to calculate individual slopes of decline on the five domains, to provide a sensitive method of analysing repeated assessment data with differential length of follow-up. The primary analysis showed that candesartan-based therapy reduced cognitive decline associated with hypertension on Attention and Episodic Memory, with a trend for Speed of Cognition; effect sizes were small-to-moderate. There were no effects on Working Memory or Executive Function (Chapter 6). The normotensive subjects showed less cognitive decline than the hypertensives (Chapter 7). These data suggest that the rate of cognitive decline associated with hypertension in older adults may be reduced by blood-pressure-lowering. Analysing individual slopes of decline on empirically-derived domains of cognition provides a sensitive and feasible methodology for assessing the effects.