Vioxx and a placebo were tested on 1,457 elderly patients with mild cognitive impairment, a group believed to be at risk of developing full-blown Alzheimer's disease. Half received the drug and half a placebo.
The results showed 6.4 percent of the patients receiving Vioxx developed Alzheimer's compared with 4.5 percent in the placebo group, the Wall Street Journal reported.
The numbers suggest Vioxx might actually increase the risk of developing Alzheimer's.
However, the study's summary said analysis of other data about the cognitive abilities of the two treatment groups shows the drug was roughly the same as the placebo, the Journal said.
Study author, Dennis Choi, head of neuroscience at Merck, concludes that Cox-2 inhibitors -- which inhibits the Cox-2 enzyme that promotes inflammation -- "does not play a significant role" in Alzheimer's disease.