Women Over 45 Experience Longer, More Irregular Menstrual Cycles

The largest study ever conducted on menstrual cycle patterns throughout a woman’s life found that women experience a significant increase in cycle length and variability starting at age 45.

At a time when research into women’s health is still sorely lacking, studies on perimenopause and the menstrual cycles of older women are even more scant. A new study aims to fill this gap.

The study, published in Scientific Reports and conducted by period tracking app Flo Health, aimed to describe the differences in menstrual cycle characteristics at different ages and the symptoms they cause, using Flo’s dataset of 19 million users.


Based on self-reported menstrual cycle and symptom information in a sample of Flo application users between the ages of 18 and 55, the study found that leading up to age 45, cycles progressively get shorter. But as of this age, as women approach menopause, their cycles become longer and more erratic.

“The importance of this study lies in the chronicling of menstrual cycle and symptom data for a large and diverse population of women spanning in age from early adulthood into perimenopausal years,” said Dr. Lubna Pal, a professor of obstetrics and gynecology at the Yale School of Medicine, who helped conduct the study.

Specifically, the study found that the proportion of individuals with irregular cycles was highest in participants aged 51-55 (44.7%), and lowest in the 36-40 age group (28.3%). Menstrual symptoms including cramps and acne were found to be less common in older participants, while headache, backache, stress, and insomnia were higher in older respondents.

Perhaps most significantly, it found that length of the menstrual cycle and related symptoms show clear age associated patterns: periods are longest in women aged 18 to 25, lasting an average duration of 5.20 days. They then get gradually shorter until age 40-44 before becoming longer again around age 45, which is when they also become much more erratic and variable — suggesting the beginning of the transition into menopause.

Irregular cycles were unsurprisingly found to be most common among older women, with nearly half of women aged 51-55 and nearly one in three aged 46-50 reporting cycle irregularity.

Up until the age of 45, the most common menstrual symptoms were cramps, breast tenderness, and fatigue. After that age, headaches became more common than fatigue.

Interestingly, mood swings were highest among the youngest and oldest respondents, but older women aged 50 and below often reported a happy mood.

While all women and individuals who menstruate inevitably go through perimenopause and menopause, the subject is massively under researched, with more than 13 times fewer studies conducted on menopause than erectile dysfunction. This knowledge gap often leads to a gap in care, preventing health care professionals from being able to understand women’s symptoms and suggest appropriate treatment.


“The wide-ranging populations’ perspectives offered in this study can help enhance population awareness of what symptoms, if being experienced by a majority, could even be construed as ‘norm,’” Pal said. “[They] may even help lessen the trepidations and stigma attached to aging, and can enhance preparedness of healthcare givers in their approach to enquiry, assessment, and efforts at optimizing care of women across the lifespan.”


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