A class of drug, called ACE inhibitors, which are used to lower blood pressure, slow the rate of cognitive decline typical of dementia, suggests research published in the online journal BMJ Open.
Furthermore, these drugs may even boost brain power, the research indicates.
The researchers compared the rates of cognitive decline in 361 patients who had either been diagnosed with Alzheimer's disease, vascular dementia, or a mix of both.
Eighty five of the patients were already taking ACE inhibitors; the rest were not.
The researchers also assessed the impact of ACE inhibitors on the brain power of 30 patients newly prescribed these drugs, during their first six months of treatment. The average age of all the participants was 77.
Between 1999 and 2010, the cognitive decline of each patient was assessed using either the Standardised Mini Mental State Examination (SMMSE) or the Quick Mild Cognitive Impairment (Qmci) screen on two separate occasions, six months apart.
Compared with those not taking ACE inhibitors, those on these drugs experienced marginally slower rates of cognitive decline.
In those whose brain power had been assessed by Qmci, which is a more sensitive screen than the SMMSE, the difference was small, but significant.
And the brain power of those patients newly prescribed ACE inhibitors actually improved over the six month period, compared with those already taking them, and those not taking them at all.
This might be because these patients stuck to their medication regimen better, or it might be a by-product of better blood pressure control, or improved blood flow to the brain, suggest the authors.
But it is the first time that there has been any evidence to suggest that blood pressure lowering drugs may not only halt cognitive decline, but may actually improve brain power.
"This [study] supports the growing body of evidence for the use of ACE inhibitors and other [blood pressure lowering] agents in the management of dementia," write the authors.
"Although the differences were small and of uncertain clinical significance, if sustained over years, the compounding effects may well have significant clinical benefits," they add.
They caution, however, that recent evidence indicates that ACE inhibitors may be harmful in some cases, so if larger studies confirm that they work well in dementia, it may be only certain groups of patients with the condition who stand to benefit.
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BMJ Open 2013;3:e002881. doi:10.1136/bmjopen-2013-002881