It included 3,297 elderly people without dementia who were followed over a two-year period. Just over 1,500 of them were taking anti-hypertensive medication.
All participants were assessed for Alzheimer's again after two years, by which time 104 of them had developed the condition.
Those using antihypertensives were found to be 36 per cent less likely to have developed Alzheimer's than those not taking the drugs.
Potassium-sparing diuretics like spironolactone or triamterene were found to be the most beneficial, reducing the risk by 74 per cent.
The researchers suggest that this protective effect might be due to increased potassium levels. Low potassium is associated with inflammation and platelet aggregation.