1. Home>
2. Specialties>
3. Neurology>
4. Summary and Comment

The Hypertension–Dementia Connection: A Chance to Make a Difference?

What is the effect of treating hypertension on the incidence of dementia or the development of Alzheimer pathology?

Two recent studies address the effect of hypertension treatment on Alzheimer neuropathology and dementia risk.

In one study, researchers examined the brains of 291 deceased elders (average age at death, 83) who had been recruited from nursing homes or elder facilities. The researchers compared the amounts of Alzheimer neuropathology (neuritic plaques and neurofibrillary tangles) in patients with histories of treated hypertension, untreated hypertension, or normotension. Only brains with no significant pathology other than Alzheimer changes were included. Subjects with treated hypertension had the least AD neuropathology, and those with normotension had the most; those with untreated hypertension were intermediate. Cognitive function during life corresponded to the neuropathology: It was best in the treated hypertension group, worst in the normotension group, and intermediate in the untreated hypertension group.

In the other study, researchers examined the effect of antihypertensive drug use, according to pharmacy records, on the incidence of all-cause dementia in more than 6000 community-dwelling elders tracked for a mean of 8 years. Because early stages of dementia can be accompanied by decreasing blood pressure, drug use was analyzed only for the period up to 4 years before dementia diagnosis. For each year of antihypertensive drug use before age 75, the risk for dementia was reduced by 8%; after age 75, it was reduced by 4%. Classes of antihypertensives did not differ significantly in their effects, but the number in each class subgroup was small.

Comment: Many studies support the association of high blood pressure in midlife with late-life cognitive decline (Lancet Neurol 2005; 4:487). Presumably, hypertension in midlife can damage cerebral blood vessels, whereas in advanced age decreased blood pressure might be a prelude to cognitive decline. If hypertension is treated, will this reduce the risk for dementia, or slow the pathological process of AD? These findings support the argument, but with a twist: The use of antihypertensive drugs decreased both clinical dementia and AD neuropathology, beyond that seen with normal blood pressure.

We still have too many unknowns, and not enough equations, to solve for a unique answer that identifies the mechanism(s) underlying these observations. Neither study included records of how much blood pressure decreased with treatment, and neither showed that a particular drug class prevented dementia or Alzheimer pathology. Whether preservation of microvascular endothelial function, improved cerebral blood flow, a direct effect on Alzheimer pathology, or another antihypertensive drug effect accounts for these findings remains unresolved. Both studies, however, support a link between vascular disease and dementia, and both suggest that taking antihypertensive drugs is a good thing, especially in the "young-old," and if blood pressure is high.

— David A. Drachman, MD

Dr. Drachman is Professor, Department of Neurology, University of Massachusetts Medical School, Worcester.

Published in Journal Watch Neurology August 25, 2009

Citation(s):

Hoffman LB et al. Less Alzheimer disease neuropathology in medicated hypertensive than nonhypertensive persons. Neurology 2009 May 19; 72:1720.

• Original article (Subscription may be required)
• Medline abstract (Free)

Haag MDM et al. Duration of antihypertensive drug use and risk of dementia: A prospective cohort study. Neurology 2009 May 19; 72:1727.

• Original article (Subscription may be required)
• Medline abstract (Free)