The risk seems to be almost exclusively associated with the hormonal IUDs—copper ones are far safer, says researcher Sanna Heikkinen from the University of Helsinki.
Although age and lifestyle are still the biggest risk factors, Heikkinen has discovered that IUDs, the contraceptive pill, hair dyes and unnecessary mammograms are responsible for many cases as well.
The biggest risk seems to be with hormonal IUDs, especially among post-menopausal women, but younger women who use other hormonal contraceptives, such as the pill, run a 32 per cent higher risk as well.
Women who dye their hair are also 23 per cent more likely to develop the cancer, she discovered.
There also seems to be some link to mammograms, routinely given to women to check for signs of breast cancer. She analysed data from 8,000 women with breast cancer—and compared the results with 20,000 other women who were healthy—and discovered that 60 per cent of the breast cancer group had had at least one mammogram before they were 50, which is the recommended age when routine screening should begin.
"Women should be more extensively informed of the harms of opportunistic mammography, such as accumulating radiation burden and the potential consequences of false positive or negative findings," said Heikkinen.