Millions of people take aspirin and other pain relievers each day to treat everything from headaches and arthritis to more serious problems, such as heart attacks and strokes.

Now a new study, published in the journal Cancer Epidemiology, Biomarkers & Prevention (Vol. 10, No. 11: 1213-1217), has found a link between some of these pain relievers and reduced breast cancer risk.

Researchers found a small reduction in breast cancer risk among women who regularly used NSAIDs (nonsteroidal anti-inflammatory drugs). This group includes aspirin and other over-the-counter medicines, such as ibuprofen, ketoprofen, and naproxen; but, it does not include acetaminophen, another type of pain reliever.

The authors say if it turns out that NSAID use does affect breast cancer risk, this would be very important because it is a step that some women may be able to take to reduce their risk.

Michelle Cotterchio, PhD, MPH, and colleagues from the University of Toronto looked at over 3,000 women diagnosed with breast cancer between 1996 and 1998, and a similar number of women without breast cancer.

All women completed the same questionnaire about their past use of pain relievers, and about other possible risk factors for breast cancer.

The risk was reduced even after researchers accounted for other factors that could influence breast cancer risk.

A previous history of daily NSAID use for at least two months was associated with a 24% reduction in breast cancer risk. The reduction was strongest for women who used them daily for more than eight years (32%). Neither the age when NSAID use started nor the number of years since starting were found to be important.

Previous studies on the subject have been mixed. More often than not, some benefit from NSAIDs has been shown. However, some large studies found no association between them and breast cancer. And while the results from this particular study are promising, it has several limitations.

Because the study asked women to remember what medicines they had taken in the past (often many years ago), it relied on their memories being accurate, which may not have been the case.

Also, the phrase "daily use for at least two months" was chosen by the authors, so it is possible some women took the drugs on a different schedule.

The results will need confirmation in future studies before recommendations can be made. And the possible benefit must be shown to outweigh any risk. NSAIDs can cause a variety of side effects, ranging from stomach and intestinal problems to increasing the risk of bleeding among aspirin users.

Even among those at risk for heart disease (a group in which aspirin and other NSAIDs have been more thoroughly studied), doctors hesitate to recommend daily usage.

Other questions will need to be answered as well. For example, if a benefit from NSAIDs is confirmed, should all women take them, or only women in certain high-risk groups? For now, NSAIDs are not specifically recommended for any group as a way to decrease breast cancer risk.

The role of these medicines in other forms of cancer is also an area of active research. Early studies have suggested they may reduce the risk of colon cancer by as much as 40% to 50%, although more studies are needed.

In fact, celecoxib has already been approved by the FDA for reducing polyp formation in people with familial adenomatous polyposis (FAP). This is a hereditary condition that greatly increases a person's risk of developing colorectal cancer.