Women who take the contraceptive pill are, generally, no more likely to develop cancer than those who do not – and, in many cases, it could even have a protective effect. In a study published in the British Medical Journal, researchers at the University of Aberdeen analysed data going back 36 years. They found that only those who had been on the pill for more than eight years were at a slightly greater risk of developing some cancers and the overall reduction in risk could be as much as 12% (BMJ 2007, DOI: 10.1136/bmj.39336.503067.be).
More than 300m women are believed to have used oral contraception since it was introduced in the early 1960s. In 1968, 46 000 UK women were recruited into a study on the long term effects, about half of whom were taking the pill. Their GPs passed on information about their health every six months.
Data were available for about two-thirds of the women, but because many had changed GP there was more for some than others. Because of this, they analysed the data in two groups. In those women for whom full data were available, they calculated that the risk of the woman developing any cancer was 3%. For the remainder, where the initial data were combined with information from the national cancer registries, the reduction was 12%.
Those who had taken the pill for more than eight years were more likely to develop cervical or brain cancer, but the risk of ovarian cancer was lower. Julie Sharp, science information manager at Cancer Research UK, points out that it is known the pill temporarily increases the risk of some cancers while reducing others. ‘This research suggests that these risks may be balanced out by health benefits over the longer term,’ she said.