A new study published today in the 'Journal of the National Cancer Institute' shows a connection between the long term use of Aspirin or Ibuprofen and an increased chance of developing breast cancer. Still, the authors of the study do not know why this is the case.

In other studies, pain relieving medications have been found to reduce the risk of colon cancer. That is one reason why researchers are puzzled by the findings in this study.

'We were expecting ibuprofen to reduce risk, and the same for aspirin,' University of Southern California researcher Sarah Marshall told 'USA Today.'

Previous studies had produced inconclusive results but seemed to indicate that the use of pain relievers led to a reduction in the chances of developing breast cancer.

The new study examined medical data on 114,460 women between the ages of 22 and 85 who were free of breast cancer. The informed the researchers how often they used aspirin or other similar pain relief medications.

The findings of the study include:

Women who took ibuprofen every day for at least five years were roughly 50 percent more likely to develop breast cancer than those who didn't.

Women who took aspirin daily for at least five years were approximately 80 percent more likely to develop breast cancer that was not sensitive to hormones than women who did not regularly consume aspirin.

Based on the study results, Marshall did not recommend that people stop taking aspirin or ibuprofen daily. However, she did add, 'I'm fairly convinced from our studies that aspirin and ibuprofen are not reducing breast cancer.'