Chicago ? Results from a large government experiment are dimming hopes that two common painkillers can prevent Alzheimer’s disease or slow mental decline in older people.

The arthritis drug Celebrex and the over-the-counter painkiller Aleve showed no benefit on thinking skills, new findings show. Earlier results from the same research showed the two drugs didn’t prevent Alzheimer’s, at least in the short term.

The experiment was halted several years early in 2004 when heart risks turned up in a separate study on Celebrex. Researchers also had noticed more heart attacks and strokes in the people taking Aleve in the Alzheimer’s prevention study.

Despite the study’s early end, there was still enough data to hint at how the drugs act on thinking and memory. The findings were posted online Monday and will appear in July’s Archives of Neurology.

“These were not the results we were hoping for,” said co-author Barbara Martin of the Johns Hopkins Bloomberg School of Public Health. “We designed this study hoping we would see a protective effect of these drugs.”

Researchers hope to continue monitoring the participants to see whether they find any delayed benefit.

Scientists have speculated that nonsteroidal anti-inflammatories, such as Aleve and Celebrex, might prevent Alzheimer’s by reducing inflammation in the brain or by other means.

Previous studies had found that people who took the drugs ran a lower risk of developing Alzheimer’s. But those were observational studies, meaning they observed people’s behavior and health. Those people may have had other healthy habits that lowered their risk.

The halted study included more than 2,000 people ages 70 and older with a family history of Alzheimer’s but no thinking problems themselves. People were randomly assigned to take standard daily doses of either Celebrex, Aleve, also known as naproxen, or a dummy pill.

At the start and annually for up to three years, they took a battery of tests. In one, they named as many grocery items as they could in one minute.

All three groups scored about the same at the start. But over time, the Aleve takers scored on average slightly lower than the people who took placebos. The Celebrex takers scored slightly lower than the placebo takers on most, but not all, of the tests.

“There’s no evidence that people should be on these drugs to prevent Alzheimer’s disease,” said Dr. David Bennett of Chicago’s Rush University Medical Center, who was not involved in the study but does similar research. “With the side effects of these drugs, people shouldn’t be taking them for this reason.”