The results from a large government experiment are dimming hopes that two common painkillers might prevent Alzheimer's disease.

New findings show that the arthritis drug Celebrex and the over-the-counter painkiller Aleve showed no benefit in terms of thinking skills. Earlier results also show that at least in the short term, the two drugs do not prevent Alzheimer's.

The experiment was halted four years ago, when a separate study on Celebrex turned up heart risks. Researchers also had noticed more heart attacks and strokes in people taking Aleve in an Alzheimer's study.

One of the study's authors' said "these were not the results we were hoping for." But the researchers say they hope to continue monitoring study participants to see if there might be a delayed benefit.

The findings were posted online and will appear in July's Archives of Neurology.