Researchers say the longer women take the oral contraception, the lower their risk of ovarian cancer.
A connection between birth control pills and lower rates of ovarian cancer has long been established.
Researchers examined the impact of newer versions of the pill on rates of ovarian cancer in young women.
Newer versions typically have lower doses of estrogen and older progestogens when compared with older versions of the pill.
The researchers found that not only were newer forms of the pill associated with a lower risk of ovarian cancer, but the protective benefits were greater with longer duration of use.
“We found a reduced risk of ovarian cancer in current or recent users of hormonal contraceptives than in former users. The reduction in risk became stronger the longer time period hormonal contraceptives were used, and the reduced risk remained several years after stopping,” Lisa Iversen, PhD, a research fellow at the University of Aberdeen in Scotland and lead author of the study, told Healthline.
“We knew from previous studies of the association between combined oral contraceptives and ovarian cancer, so our results might have been expected. However, previous studies were based on women who were mostly older than reproductive age and therefore former users of oral contraceptives who would have used older products,” she said.
“It was necessary to conduct our study to investigate whether hormonal contraceptive use in women currently of reproductive age would still be associated with a reduced risk of ovarian cancer,” Iversen said.
To undertake their research, Iversen and her colleagues examined data from almost 1.9 million women in Denmark between ages 15 and 49.
The women were placed into three categories: women who had never used the pill, current or recent users of the pill who had stopped in the past 12 months, and former users who had stopped taking the pill more than 12 months ago.
Combined oral contraceptives accounted for 86 percent of use of hormonal contraceptives.
The researchers took into account factors such as age, family history of ovarian cancer, and education.
They found that ovarian cancer rates were highest among the women who had never taken the pill.
Women who had taken the pill were found to have lower rates of ovarian cancer.
The researchers estimate that based on their findings, hormonal contraceptives prevented approximately 21 percent of ovarian cancers among the women who took the oral contraceptive pill.
The researchers didn’t find firm evidence of a protective effect against ovarian cancer for women who had taken progestogen-only products. But Iversen says only a small sample of women in the study exclusively used such forms of birth control pills, so the data may not be strong enough to give a good indication.
There are 61 million women of reproductive age in the United States.
Of these, experts estimate slightly more than 15 percent, or approximately 9 million women, use birth control pills.
In 2018, the American Cancer Society estimates 22,000 women in the United States will receive a diagnosis of ovarian cancer, and 14,000 will die from the condition.
Ovarian cancer is the fifth cause of cancer deaths among women. It leads to more deaths than any other form of cancer of the female reproductive system.
Nearly all research on birth control pills and cancer has been observational and therefore can’t definitively prove whether the pill can prevent (or cause) cancer.
But according to the National Cancer Institute, studies have provided consistent evidence that for women who take birth control pills, risks of breast and cervical cancers increase, and risks of endometrial, ovarian, and colorectal cancer decrease.
Researchers have hypothesized a number of potential reasons why the birth control pill is associated with lower risks of some cancers.
In the case of ovarian cancer, it’s likely because it suppresses ovulation.
“The total number of ovulation cycles that a woman has in her reproductive life is correlated with the risk of ovarian cancer. Anything that decreases the number of ovulations is associated with decreased risk of ovarian cancer. This includes pregnancy… breastfeeding… and use of the oral contraceptive pill. The benefits of oral contraceptive pills fade with time after the woman is no longer using the pill,” Dr. Gary Scott Leiserowitz, chair of the department of obstetrics and gynecology at the University of California at Davis, told Healthline.
Previous research has found women who use oral contraceptives have a 30 to 50 percent lower risk of developing ovarian cancer than women who have never taken the pill.
This protection increases with the amount of time a woman takes birth control pills.
Past studies on older forms of the birth control pill suggest this protective benefit can last up to 30 years after a woman stops taking it.
Iversen’s study didn’t determine the duration of protective effects of contemporary versions of the birth control pill, as the study didn’t examine older women. But Iversen says the findings should still be of value to younger women.
“Our findings of a reduced risk of ovarian cancer associated with contemporary combined oral contraceptives are reassuring for women currently of reproductive age,” she said.
With the exception of cervical cancer, there’s no way to reliably and simply screen for any gynecologic cancer.
Many ovarian cancers aren’t found until they’ve spread, as symptoms such as back pain, bloating, vaginal bleeding, and discharge can often be mistaken for other things.
“There is no good screening test for ovarian cancer, which is the deadliest gynecologic cancer. We need to use whatever tools we have available to prevent it from developing. Oral contraceptive pills are one of these tools that is often overlooked,” Dr. Dineo Khabele, director of the division of gynecologic oncology at the University of Kansas Medical Center, told Healthline.
Newer versions of the birth control pill provide more protective benefits against ovarian cancer than older versions of the pill.
The reduced risk was strengthened the longer oral contraceptives were used.
The benefit was seen several years after stopping the pill.