BioEd Online

The contraceptive pill cuts women's risk of suffering cardiovascular disease, according to one of the most extensive studies ever done. The result challenges a long-held view that the hormones it contains are bad for the heart.

Numerous past studies have suggested that the oral contraceptive increases women's chances of heart disease. But a smattering of more recent investigations have called this assumption into doubt.

Rahi Victory of Wayne State University in Detroit, Michigan, and his colleagues mined the vast amount of medical data collected for the US Women's Health Initiative, a study that revealed the health risks posed by hormone replacement therapy (HRT). The database contains information on around 162,000 women and includes data about whether they took the pill and how often they suffered several diseases in middle and old age.

The team calculated that women who had taken the pill at some point in their lives were 8% less likely to suffer any form of cardiovascular disease, including conditions such as heart attacks and high cholesterol. "Everything is lower in the oral contraceptive users," says Victory, who reported the results on 20 October at the meeting of the American Society for Reproductive Medicine in Philadelphia.

The beneficial effects were seen only in women who had taken the pill for more than one year. The benefits increased the longer that they took the pill and were independent of other factors in their lives, such as not smoking.

Experts say the study conclusions will need to be published and scrutinized in more detail before the medical community can respond.

Hormonal protection

Victory suggests that previous studies missed the cardiovascular benefits because they were smaller or less comprehensive. But his findings fit, he says, with a growing body of evidence that shows that oestrogen, one of the two hormones in the pill, helps protect blood vessels and prevent the growth of artery clogging deposits.

The researchers' findings also seem to contradict those from the Women's Health Initiative itself, which showed that older women taking HRT, a similar cocktail of oestrogen and progestin, increase their risk of cardiovascular disease.

But Victory suggests that older women may already be on the road to heart problems when they start taking HRT. In younger, healthier women taking the pill, the hormones may exert some protection.

Despite the findings, women who know they are at a high risk of heart disease should not start taking the contraceptive pill, Rahi says, because it is not known whether they would gain the same benefit as the team found in the broader population. It is simply that women already on the pill may be reaping unexpected health benefits.

In a second analysis, the team found that women who had taken the pill were also at lower risk of getting cancer. In particular, it found almost a 20% decrease in the incidence of ovarian and endometrial cancer. The women were also at no increased risk of breast cancer, the team found, contrary to some earlier studies.