March 12, 2010— -- Taking "the pill" won't increase a woman's risk of death -- in fact, oral contraceptive users may live longer, researchers say.
In a population-based study of women in the U.K., death from any cause was 12 percent lower among birth control pill users than among those who never took the drugs, Dr. Philip Hannaford of the University of Aberdeen in Scotland and colleagues reported online in BMJ.
"This is very reassuring and enables us to say with confidence to women that if they choose to use the pill as their contraceptive, they are highly unlikely to do long-term damage to themselves," Hannaford said in an e-mail to MedPage Today.
Previous studies have shown no increased risk of mortality with oral contraceptive use, but the researchers said they didn't have a long enough follow-up.
So they assessed data from the Royal College of General Practitioners' Oral Contraceptive Study, which began in 1968. It contains mortality data from general practitioners and National Health Service central registries on 46,112 women who were followed for 39 years.
A total of 1,747 deaths occurred in patients who never used oral contraceptives, and 2,864 occurred among those who had. The researchers noted that they were able to include three times as many deaths in their assessment as previous studies. The women studied used birth control pills for an average of 44 months.
Those who did use the pills had a significantly lower rate of death from any cause. They also had significantly lower rates of death from all cancers -- including bowel cancer, uterine cancer and ovarian cancer -- the researchers said.
Investigators also found lower rates of death from circulatory disease, ischemic heart disease, and other disease among women who had used birth control pills.
"We do know that pill users have a lower risk of death from some cancers which persists for many years after stopping, [which] could account for the lower risk of cancer deaths in pill users," Hannaford said.
"It is difficult, however, to see how the pill might reduce the risk of circulatory disease in the long-term, other than by another mechanism such as screening or monitoring."
Yet women on the pill did have higher rates of violent deaths. The researchers said they had no explanation for this association.
In more detailed analyses, the researchers did see higher rates of death among contraceptive users in certain subgroups. For example, mortality was increased in the youngest age group. Women under 30 who took the pill had almost a three-fold greater rate of death from any cause than never-users.
After age 50, however, the rate of death among ever-users was significantly lower than it was among never-users.
There was also an increased risk of death from any cause among ever-users under 45 who had stopped taking oral contraceptives about six years previously. But the same risk wasn't seen in those with more distant use.
Finally, the researchers found no association between overall mortality and duration of oral contraceptive use.
One caveat is that the study may have been limited by "healthy survivorship" -- that is, women who took the pill were on average healthier than the national average.
"It isn't clear whether the lower longer-term risk of death in ever users was a true effect of the pill or rather some difference in the characteristics of women choosing to use the pill," Hannaford said.
"For example, they might be monitored for side effects of the pill and may be more likely to be screened for disease than non-users."
Also, the researchers didn't assess risk of death according to the type of hormone used in the pills the women took.
Hannaford cautioned that contraceptive choices should be based on contraceptive effectiveness, acceptability, and ease of use, among other factors -- not possible reductions in disease later in life.
"I would never recommend that someone use the pill simply to reduce their risk of disease later in life," he said. "However ... if the choice is the pill, this decision does not increase a woman's risk of long-term death. Indeed it may even have some benefits."