Some studies have suggested that over-the-counter pain medications such as Aleve and Celebrex may help people avoid Alzheimer's disease. But a new experiment with a control group did not find the effect.

Researchers studied more than 2,100 people at six clinics around the country. The subjects were older than 70 and had a family history of Alzheimer's, but no signs of the degenerative disease. They were randomly put on courses of naproxen, celecoxib or a placebo pill and studied for up to four years, though many were in the study less than two years.

The study's authors said that they did not see lower rates of dementia in any of the groups, though they said it could be that the effect does not show up so quickly.

In the placebo group, about 1 percent showed signs of Alzheimer's dementia by the end of the study. It was about 1.8 percent for Celebrex and 2 percent for Aleve.

The study did not investigate the effect of ibuprofen, which is another common pain medication.