Painkillers such as aspirin are effective in reducing prostate enlargement, a common condition among older men, according to new research. However, doctors warn that men should not self-medicate for this purpose, as anti-inflammatory drugs sometimes cause severe gastrointestinal bleeding.

Though 80 percent of the 2,500 men who participated in the research took aspirin, the same effect was observed in those who were taking ibuprofen, naproxen and such cox-2 inhibitors as Celebrex, noted study leader Jenny St. Sauver, an epidemiologist at the Mayo Clinic. The men completed annual questionnaires from 1990 to 2002.

Enlarged prostate, or benign prostatic hyperplasia, is common -- "as common a part of aging as gray hair," according to the National Institute of Diabetes and Digestive and Kidney Diseases. It affects about 25 percent of men aged 40 to 50, and nearly 50 percent of those 70 and older. It typically causes the urge to urinate frequently and related problems. Severe cases can cause serious problems over time. Urine retention and strain on the bladder can lead to urinary tract infections, bladder or kidney damage, bladder stones, and incontinence.

The investigators found that the men who regularly took any non-steroidal anti-inflammatory drug (NSAID) experienced about 50 percent less prostate enlargement. Also, moderate to severe urinary problems were reduced by 35 percent in this group.

NSAIDs may combat prostate enlargement by reducing prostate cell growth or spurring the natural death of the cells, the researchers hypothesized. It is also possible that the drugs' anti-inflammatory action is responsible for the beneficial effect.

However, St. Sauver emphasized that men should not begin taking painkillers for this purpose without consulting their doctors, since they may have unwanted side effects. In particular, NSAIDs can raise the risk of gastrointestinal bleeding.

St. Sauver called for further study to determine whether NSAIDs should be used to prevent prostate enlargement at all -- and if so, to determine the optimal dosage and other prescribing information.