The 1,362 Caucasian men in this study were followed for an average of 5.5 years. Of the 569 men who reported using an anti-inflammatory agent daily, 23 developed prostate cancer compared with 68 of 793 men in the same study who did not use such a medication daily.

"These numbers mean the proportion of men who used nonsteroidal anti-inflammatory drugs daily and developed prostate cancer was about one-half that of men who did not use nonsteroidal anti-inflammatory drugs daily -- four percent compared to nine percent," says Rosebud Roberts, M.D., lead researcher on the study.

"Further, the association between nonsteroidal anti-inflammatory drugs and prostate cancer appears to be stronger in older men," says Dr. Roberts. "The risk of prostate cancer among nonsteroidal anti-inflammatory drugs users was 12 percent lower in men age 50 to 59 years, 60 percent lower in men 60 to 69 years, and 83 percent lower in men age 70 to 79 years compared to men in those same age groups who did not use nonsteroidal anti-inflammatory drugs daily."

These preliminary results need to be followed by more research, cautions Roberts: "Although our findings provide important information that nonsteroidal anti-inflammatory drugs may protect against prostate cancer, they are not conclusive."

"More research needs to be done to show that the results we saw in our study were not unique to our study but can be confirmed in other similar studies," she said. "We also need to determine the duration and dosage use that provides protection against prostate cancer and to better understand the biologic mechanisms underlying the association between nonsteroidal anti-inflammatory drugs and prostate cancer."

Dr. Roberts added that because the study included only Caucasian men from one region, it is not known whether the findings apply to men of all races.

"While our findings complement previous studies that nonsteroidal anti-inflammatory drugs help protect against breast and colon cancers, and possibly against prostate cancer, there are also negative side effects of nonsteroidal anti-inflammatory drugs that need to be considered and monitored in people who take nonsteroidal anti-inflammatory drugs on a daily basis," she says.

About 189,000 men in the United States will be diagnosed with prostate cancer this year. About 30,200 men will die of the disease.

The current study was part of a larger Mayo Clinic study that monitored lower urinary tract symptoms in 2,115 men from Olmsted County of southeastern Minnesota. The men ranged in age from 40 to79 years at the onset of the study in 1990.

The findings about the association between prostate cancer and nonsteroidal anti-inflammatory drugs are based on information obtained from a subset of 1,362 men in the study who were age 50 years and older at study outset. These men reported using 40 different prescription and over-the-counter nonsteroidal anti-inflammatory drugs at the beginning of the study and during follow-up.