Women's use of oral contraceptives for fewer than eight years reduces overall cancer risk by up to 12%, but use of contraceptives for more than eight years increases cancer risk by 22%, according to a study published on Tuesday in the British Medical Journal, London's Times reports (Hawkes, Times, 9/12).

For the study, Philip Hannaford of the University of Aberdeen and colleagues studied the records from the Royal College of General Practitioners of 46,000 women -- about half of whom began using oral contraceptives in 1968 -- over a 36-year period in the United Kingdom. About half of the women in the study never used oral contraceptives, Reuters reports (Reuters, 9/12). According to the Scotsman, researchers accounted for factors such as age, smoking and social class (Moss, Scotsman, 9/12).

General practitioners provided researchers with information on the women's health every six months, according to a BMJ release. Researchers analyzed two sets of data -- one that included recorded cancers among women who remained with their original general practitioner and another that also included cancers recorded in National Health Service registries after women left their original physicians. About three-quarters of the women in the study were included in the NHS registries (BMJ release, 9/11).

Using the data reported to general practitioners and NHS, which included cancers recorded until 2004, researchers found that women who took oral contraceptives for eight years or less had a 12% reduction in overall cancer risk, which equates to one fewer case of cancer a year for every 2,200 women who used oral contraceptives. Among the approximately one-quarter of contraceptive users who took the drugs for more than eight years, the risk of overall cancer increased by 22%, the study found. Using the smaller set of data, which included information from general practitioners up to 1996, researchers found that contraceptive use reduced cancer risk by 3% (Times, 9/12).

The study found no evidence of decreased or increased risk of breast cancer among short-term contraceptive users (Times, 9/12). Statistically significant reduced risks of large bowel, ovarian and uterine cancer were evident among contraceptive users, BBC News reports. Evidence also suggest that women who took oral contraceptives were protected from the risk of developing cancers for at least 15 years after they stopped using the drugs (BBC News, 9/11).

Reaction
Hannaford said, "My message for women is that if you want to use the pill for contraceptive reasons, then go ahead. It will not increase your lifetime risk of developing cancer." He added that if women "want to use it for longer than eight years, then the risk increases slightly but that does not mean they have to stop using it."

Maria Leadbeater, a nurse specialist at Breast Cancer Care, said the findings would be welcomed by the thousands of women in the United Kingdom. She added, "From talking to women on our helpline, we know the anxiety that concerns over the pill can cause. This research will be a great reassurance to them." Toni Belfield of the Family Planning Association said the "study further confirms that for the majority the benefits [of oral contraceptives] far outweigh any risks" (Moss, Scotsman, 9/12).

The study is available online.