Analysis of the Atherosclerosis Risk in Communities (ARIC) study cohort supports an association between elevated blood pressure (BP) in midlife and increased cognitive decline in older age.
In an editorial accompanying the study published in JAMA Neurology, Philip Gorelick (Michigan State University College of Human Medicine, Grand Rapids, USA) says that ARIC “provides a unique opportunity to understand the role of raised BP on cognition during a 20-year period.”
A total of 13,476 White and African–American participants completed cognitive assessments at the second study visit in 1990–1992 (at which point more than half had prehypertension or hypertension), and 58% of these completed the third cognitive assessment at the fifth visit in 2011–2013.
Over the 20-year period, the global cognition z score declined by a significant 0.056 points more in participants who had hypertension at the second visit than in those who had normotension, and by a nonsignificant 0.040 points more in those with prehypertension.
Rebecca Gottesman (Johns Hopkins University School of Medicine, Baltimore, Maryland, USA) and study co-authors equate this to a 6.5% additional decline with hypertension beyond that caused by ageing alone. They say that “a shift in the distribution of cognitive scores, even to this degree, is enough to increase the public health burden of hypertension and prehypertension significantly.”
Moreover, they observe that participants lost from the study tended to have the highest BP and the worst cognitive scores, suggesting that the true effect of midlife hypertension could be larger.
The effect of hypertension on cognition was largest for the Digit Symbol Substitution Test, with z scores in hypertensive and prehypertensive participants declining by a significant 0.079 and 0.046 points, respectively, more than scores in normotensive participants.
Only hypertensive participants had accelerated decline in the Word Fluency Test, by 0.057 points more than normotensive participants, while declines in Delayed Word Recall Test scores were accelerated in hypertensive and prehypertensive participants, but not significantly so.
Of note, hypertensive participants who were taking antihypertensives at the second visit had cognitive declines that were intermediate between that of the hypertensive and prehypertensive participants.
In his editorial, Gorelick says that, to date, the evidence for lowering BP to preserve cognition is strongest for middle-aged and younger elderly people, whereas the benefits or otherwise are unclear in older people. Until more evidence emerges, he says that “on a case-by-case basis, the practitioner will need to balance the benefit of BP lowering on cardiovascular disease risk reduction with the possible benefit or risk to cognition.”
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