SAN DIEGO — Women whose menstrual periods are irregular, such as those who go more than five weeks between periods, may be at increased risk of dying from ovarian cancer, a new study suggests.
In the study, women with irregular menstrual cycles at age 26 were about twice as likely to die from ovarian cancer in their 60s compared with women with regular periods. The researchers counted menstrual cycles as "irregular" if they lasted more than 35 days (typically, cycles last 21 to 35 days). The study also counted cycles as irregular if an egg was not released, known as anovulation.
The findings held even after the researchers took into account factors that may affect women's risk of ovarian cancer, such as age, weight, and use of fertility drugs or birth control pills. The researchers also ruled out infertility as an explanation for the findings, since all of the more than 14,000 women in the study had given birth to a child. [5 Things Women Should Know About Ovarian Cancer]
If future research confirms the link, women with irregular periods could be recommended for ovarian cancer screening, the researchers said.
“Unfortunately, there is no reliable method for early diagnosis or screening [of ovarian cancer], and symptoms like abdominal pain and bloating often do not come to a woman's attention until the cancer has spread," said study researcher Barbara Cohn, director of Child Health and Development Studies at the Public Health Institute in Berkeley, Calif.
The new findings "may help [with] earlier diagnosis and perhaps lead to a strategy to prevent ovarian cancer," said Cohn, who presented the findings here today (April 9) at the meeting of the American Association for Cancer Research.
Previously, some researchers suggested that less-frequent ovulation would reduce the risk of ovarian cancer, but the new findings contradict this hypothesis.
Researchers don't know why irregular menstrual cycles might increase the risk of dying from ovarian cancer. It's possible that hormones play a role; for example, the ovaries in these women may be exposed to lower amounts of the hormone progesterone, which is released after ovulation and may protect against ovarian cancer, Cohn said.
The researchers hope the findings will prompt more studies to both replicate the results and investigate the potential role of irregular menstrual cycles in ovarian cancer risk. Such research may help scientists understand more about how ovarian cancer develops, Cohn said.
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Rachael is a Live Science contributor, and was a former channel editor and senior writer for Live Science between 2010 and 2022. She has a master's degree in journalism from New York University's Science, Health and Environmental Reporting Program. She also holds a B.S. in molecular biology and an M.S. in biology from the University of California, San Diego. Her work has appeared in Scienceline, The Washington Post and Scientific American.