By: Thomas Pickering, MD, DPhil, FRCP, Director of Integrative and Behavioral Cardiology Program
of the Cardiovascular Institute at Mount Sinai School of Medicine, New York.

It is well recognized that hypertension contributes to the development of dementia in older people. One previous study called SHEP (Systolic hypertension in the Elderly Program) found that treatment with a diuretic lowered the risk of stroke, but did not affect the onset of dementia. Syst-Eur, a second study of the effects of treatment in hypertensives over the age of 60, in which a calcium channel blocker (nitrendipine) was the active drug, also found that treatment lowered the risk of strokes and heart attacks. The study compared the outcomes of 1,238 patients who were treated with nitrendipine with 1,180 who were given placebo. Dementia was evaluated by giving the patients a series of tests of their brain function at the start and end of the study. Dementia was classified as vascular in origin if a CT scan of the brain showed areas of vascular damage, and as Alzheimer's if there was no focal damage. Most of the cases of dementia were due to Alzheimer's disease. The main finding of the study was that the rate of development of dementia in the patients on blood pressure lowering treatment was half that in the placebo group.

Doctor's comments

There are two common sorts of dementia - multi-infarct dementia, where a CT scan shows evidence of numerous small strokes occurring from vascular disease, and Alzheimer's disease, where the scan just shows shrinkage of the brain. Hypertension is known to be a cause of vascular dementia, but it is less clear to what extent it can lead to Alzheimer's disease. What was surprising about this study was that the calcium channel blocker appeared to have the greatest effect in preventing the Alzheimer's type of dementia. This contradicts an earlier non-randomized study which claimed that calcium channel blockers may actually cause dementia. An interesting possibility is that the beneficial effects of the calcium channel blocker on brain function may not be due to the reduction of blood pressure, because the other large study of the effects of lowering blood pressure in older people (SHEP), which used a diuretic rather than a calcium channel blocker, found no prevention of dementia in the treated group.

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