Painkillers such as Aspirin and ibuprofen may not help prevent Alzheimer's disease in older people as thought, but could delay it, a new study suggests.

It was hoped that the drugs, known as non-steroidal anti-inflammatories or NSAIDS, could help prevent Alzheimer's disease, which has been linked with inflammation.

In Wednesday's online issue of the journal Neurology, researchers said they found that the risk of dementia was actually higher among heavy users of NSAIDS in their study. They looked at 2,736 people in the U.S. who had an average age of 75 and showed no signs of dementia when the study began.

After 12 years of follow up, 476 people developed Alzheimer's disease or dementia, the researchers said.

The risk of developing dementia among the 351 people with a history of heavy use of the medications was 66 per cent higher than among people with little or no use of the drugs. (Heavy use was defined as having prescriptions for NSAIDs at least 68 per cent of the time over a two-year period.)

"A key difference between this study and most of those done earlier is that our participants were older," said study author Dr. John Breitner, of the Department of Veterans Affairs and the University of Washington School of Medicine in Seattle.

Previous studies on younger subjects suggested NSAIDs may delay the onset of Alzheimer's dementia.

"Conceivably, such delay could result in increased incidence of Alzheimer disease incidence in late old age," the study's authors wrote.

More research is needed to understand the results more clearly, Breitner said.

Since dementia becomes clinically apparent in old age, researchers will need to study younger patients over a longer period of time to tell whether the drugs truly help in preventing or delaying the disease, Dr. David Bennett of Rush University Medical Center in Chicago and Rachel Whitmer, a research scientist at Kaiser Permanente in Oakland, Calif., agreed in a journal commentary.

Nearly 300,000 Canadians are living with Alzheimer's disease, which slowly leads to memory impairment, behavioural changes and dementia, affecting how people understand, think, remember and communicate.