ST. PAUL – A new study shows that nonsteroidal anti-inflammatory drugs (NSAIDs) such as the pain relievers ibuprofen and naproxen do not prevent Alzheimer's disease, but they may instead delay its onset.

The study suggests a need for re-interpretation of earlier findings that suggested NSAIDs can prevent the disease. The research is published in the April 22, 2009, online issue of Neurology®, the medical journal of the American Academy of Neurology.

Researchers identified 2,736 members of Group Health, an integrated healthcare delivery system, who did not have dementia when they enrolled in the study at an average age of 75. The investigators followed these people for 12 years to see if they developed Alzheimer's or dementia. They checked Group Health pharmacy records for NSAID prescriptions and also asked participants about their use of NSAIDs.

Of the participants, 351 people had a history of heavy use of NSAIDs at the start of the study, and another 107 people became heavy NSAID users during the follow-up period. Heavy use was defined as having prescriptions for NSAIDs 68 percent of the time or more over a two-year period.

During the study, 476 people developed Alzheimer's disease or dementia. The risk of developing dementia among heavy NSAID users was 66 percent higher than among people with little or no NSAID use.

"A key difference between this study and most of those done earlier is that our participants were older," said study author John C. S. Breitner, MD, MPH, of the Department of Veterans Affairs and the University of Washington School of Medicine in Seattle. "It has been argued for some time that NSAID use delays the onset of Alzheimer's disease. It would follow that studies looking at younger people who use NSAIDs would show fewer cases of Alzheimer's, while in groups of older people there might be more cases, including those that would have occurred earlier if they had not been delayed."

"This is one interpretation of the results, but other explanations are possible," cautioned Breitner, who added, "We must not ignore the fundamental finding, which is an increase in the risk of dementia in the NSAID users. We need further research to understand that result more clearly."

The study was supported by the U.S. Department of Veterans Affairs, the National Institutes of Health, and the Paul B. Beeson Career Development Awards in Aging Research Program.

The American Academy of Neurology, an association of more than 21,000 neurologists and neuroscience professionals, is dedicated to improving patient care through education and research. A neurologist is a doctor with specialized training in diagnosing, treating and managing disorders of the brain and nervous system such as multiple sclerosis, restless legs syndrome, Alzheimer's disease, narcolepsy, and stroke.

For more information about the American Academy of Neurology, visit www.aan.com.