A handful of studies have examined the relationship between over-the-counter pain medications such as ibuprofen and aspirin and breast cancer. The jury is still out on whether or not there is a connection, so researchers from several California universities decided to take a fresh look at the question.

What the researchers wanted to know: Is there a connection between use of aspirin and ibuprofen and breast cancer risk?

What they did: The researchers followed more than 114,000 California women between the ages of 22 and 85 for at least five years. All of the women were cancer-free at the beginning of the study and completed a questionnaire that asked them how often they took over-the-counter pain relievers and for how long they had been taking them. The researchers asked about all pain relievers, including acetaminophen (such as Tylenol), but they concentrated their analysis on ibuprofen (such as Motrin or Advil) and aspirin, which belong to a class of pain relievers called nonsteroidal anti-inflammatories (NSAIDS). They used the California Cancer Registry to determine if and when the participants were diagnosed with breast cancer, as well as characteristics of the cancer.

What they found: Regular use of aspirin or ibuprofen did not change breast cancer risk until the pills had been taken for more than five years. Long-term ibuprofen users had a 51 percent greater risk of developing breast cancer. Long-term aspirin users had a very slightly (and possibly insignificant) lower risk of developing estrogen and progesterone-positive breast cancer but an 81 percent higher risk of estrogen and progesterone-receptor-negative breast cancer. (Estrogen and progesterone-positive breast cancer means that the growth is at least partially driven by the female hormones estrogen and progesterone.)

What it means to you: This study contradicts others that have shown that NSAIDs can decrease a woman's risk of breast cancer. But don't throw your pills away yet. The researchers say that they don't know why they got these results because there's nothing in the drugs that's known to cause cancer. They say that women who have been prescribed ibuprofen or aspirin should talk to their doctor but not necessarily change their medication, and should wait for more research on the subject.

Caveats: This study showed a link between breast cancer and certain types of pain relievers. However, that does not mean that the pain relievers caused the cancer. There could have been some separate condition that the researchers did not take into account that caused the cancers.

Find out more: The Mayo Clinic's website has a page that explains controllable factors, including over-the-counter pain medications that can increase or reduce your risk of breast cancer.

Read the article: Marshall, S.F. et al. "Nonsteroidal Anti-Inflammatory Drug Use and Breast Cancer Risk by Stage and Hormone Receptor Status." Journal of the National Cancer Institute. Vol. 97, No. 11, pp. 805-812.

Abstract online: http://jncicancerspectrum.oupjournals.org