More evidence has emerged that the common pain-killer aspirin may be able to slow or block the onset of Alzheimer's disease.
New US findings suggest that elderly patients taking low doses of aspirin for other conditions were half as likely to develop Alzheimer's than those who did not take aspirin regularly.
The new study is published in the journal Neurology, and involved an assessment of 5,000 patients over the age of 65.
Dr John Breitner and colleagues at the Veterans Administration Puget Sound Health Care System in Seattle, Washington, carried out the study.
Patients were checked for early symptoms of the disease, which causes dementia and disturbance to memory. The condition gradually worsens, with patients becoming unable to recognise loved ones and incapable of minding themselves.
The research group also examined whether the patients in the study had regularly taken aspirin or other non-steroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen. They found that of the 3,227 patients who were still alive at the end of the study period, 104 had Alzheimer's.
Patients who had been taking aspirin for joint pain, arthritis or in a low-dose regime to prevent blood clots were found to be half as likely to have Alzheimer's as those who did not take these tablets.
The researchers found that the benefits only seemed to apply for those patients who had been taking the pain-killers over a long period, well before any Alzheimer's symptoms began to appear.
"Our results suggest that long-term NSAID-use may reduce the risk of Alzheimer's disease provided the use occurs well before the onset of dementia," Dr Breitner said.
The Alzheimer's Research Trust welcomed the findings, saying that this work confirmed previous results that aspirin could have an effect on Alzheimer's onset.
The trust warned, however, that people should not self-prescribe medication to ward off symptoms. Long-term use of aspirin and other NSAIDs could cause serious side effects, including stomach bleeding, ulcers and kidney problems.
"While this type of research helps us to understand more about Alzheimer's, and provides hope to people affected by dementia, unfortunately there is a long way to go before we might find a fully-effective treatment or way of preventing the disease," said the trust's chief executive Ms Harriet Millward.