High blood pressure is a major risk factor for vascular cognitive impairment and is emerging as a potential risk factor for Alzheimer's disease (AD), concludes a new statement from the American Heart Association.
"We know treating blood pressure is important for reducing cardiovascular events," chair of the writing committee, Costantino Iadecola, MD, Brain and Mind Research Institute at Weill Cornell Medicine, New York, commented to Medscape Medical News. "The relationship to dementia is not fully established, but putting all the data together on the issue it does appear that increased blood pressure in midlife is bad for the brain."
He added, "Epidemiological studies suggest that treating blood pressure in midlife should have a positive effect on cognitive impairment later in life. But this has not yet been proven definitively."
Dr Iadecola emphasized the need for prospective randomized trials to determine the exact relationship between blood pressure and dementia and whether lowering blood pressure can protect against later dementia. One such trial — SPRINT MIND — is expected to report next year. "Until then, we should treat blood pressure judiciously on a patient-by-patient basis," he concluded.
The statement was published online in Hypertension on October 10.
As background, Dr Iadecola explained that because both hypertension and dementia were very common disorders and it is known that chronic arterial hypertension is linked to vascular cognitive impairment, "we thought it was timely to conduct a comprehensive review of the literature on the issue of hypertension and dementia, including AD. The present statement therefore seeks to provide an appraisal of the contribution of hypertension to age-related cognitive dysfunction."
"The evidence suggests a very strong link between hypertension during midlife (age 50-60) and dementia later in life (age 80 plus). And this is for Alzheimer's as well as vascular dementia."
He noted that while this has been suggested before in individual reports, this is the first time all the evidence has been reviewed so comprehensively. In addition, trials have not looked at each individual age groups, and most studies have been retrospective.
"Many of the individual studies are difficult to interpret because they have not used cognition as a primary endpoint — it has generally been a secondary endpoint and different definitions have been used."
Dr Iadecola was not in favor of recommending one value for the optimal blood pressure for the whole of life.
"This probably changes with age," he said. "In the elderly, we think a slightly higher blood pressure may be beneficial, as when carotid stenosis starts to develop then you need a higher pressure to push blood through the brain. A pressure of 120/80 may be too low for someone with severe cerebrovascular disease. So I think the ideal blood pressure needs to be personalized."
He says he finds it "bizarre" that "in the age of precision medicine when we are sequencing genes to personalize medical care something as simple as blood pressure is still viewed as a one size fits all."
In the statement, the authors note that hypertension disrupts the structure of cerebral blood vessels, promotes atherosclerosis, and impairs vital cerebrovascular regulatory mechanisms. These vascular changes increase the susceptibility of the brain to ischemic injury, especially in vulnerable white matter regions critical for cognitive function, and may promote AD pathology.
The evidence to date points strongly to a deleterious influence of midlife hypertension on cognitive function in midlife and late life. Executive function and processing speed seem to be the cognitive domains most affected, but memory can also be impaired, they report.
On the subject of aging, they say, "Although the data are not conclusive, there is evidence of an association between higher late-life BP [blood pressure] and better cognition, highlighting the complexities of recommending uniform levels of BP across the life course."
In addition to aging, other factors that may affect the relationship of hypertension in cognitive decline are menopausal status, APOE ε4 genotype, insulin resistance, and systemic inflammation.
The statement says that the effects of hypertension treatment on cognitive function is less clear. "Evidence from randomized, double-blind, clinical trials that treatment of high BP at any stage over the life course improves cognition is far from conclusive."
Regarding AD, it states: "An intriguing relationship has emerged between hypertension and AD, raising the prospect that a chronic elevation in BP aggravates AD pathology, contributing to dementia. These findings are critically important because they raise the possibility that treatment of hypertension may also contribute to reduce the development or progression of AD.
"Because no evidence-based recommendations can be made at this time, treatment of high BP in midlife and judicious use of antihypertensives in late life, taking into account cerebrovascular status and comorbidities, seem justified," the authors conclude.
Hypertension. Published online October 10, 2016. Full text
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Cite this: New AHA Statement on Hypertension and Cognitive Function - Medscape - Oct 13, 2016.