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Key takeaways:
- Withings data from 69,000 women across 11 countries shows sleep quality falls for 76% of women in the week before their period.
- The decline is characterized by a loss of deep sleep and a rise in night-time heart rate, driven by post-ovulation progesterone increases.
- Women in the US experience the most significant disruptions, recording the lowest premenstrual sleep scores and highest night-time heart rates in the study.
- Women using hormonal contraception show a noticeably smaller impact on sleep quality and heart rate compared to those with natural cycles.
A new analysis of 469,000 menstrual cycles from 69,000 women not using hormonal contraception reveals that sleep quality falls in the week before a period for 76% of women. The data, gathered by Withings connected devices, spans 11 countries and highlights consistent physiological shifts during the premenstrual week.
Globally, the average sleep score drops 3.4 points compared to the days immediately following a period. Nighttime heart rate rises in 90% of women by an average of 2.8 beats per minute (bpm). Among the 11 countries studied, women in the US fare the worst. In the week before their period, US women see their average sleep score fall to 68.5—the lowest in the study—along with an average of 5.4 sleep interruptions a night and a night-time heart rate of 68.6 bpm.
“Looking across 469,000 cycles, the same pattern appears again and again: in the days before a period, nighttime heart rate climbs and sleep becomes lighter, and the women whose heart rate rises most see the biggest drop in sleep quality,” says Livia Robic, women’s health expert at Withings, in a release. “These are small shifts, but they are remarkably consistent from one country to the next. Knowing the pattern is normal and predictable can help women make sense of a restless night or a heavier morning on the scale, rather than worry about it.”
The analysis indicates the sleep loss is primarily in quality rather than quantity. Women sleep only about five minutes less in the premenstrual week, but deep sleep falls by 1.8 percentage points (approximately 5% of usual deep sleep) and is replaced by lighter sleep. Heart rate variability, a marker of recovery, also drops by 3 milliseconds.
These disruptions align with known physiological changes across the menstrual cycle. After ovulation, the body produces progesterone, which raises core body temperature and shifts the nervous system toward a more alert state, pushing heart rate up and heart rate variability down. Because the body must cool down to enter deep sleep, this warmer state leads to lighter sleep. The data shows this dip begins just after estimated ovulation and bottoms out three to five days before the period.
The analysis also evaluated 3,362 women using hormonal contraception across the 11 countries, finding a much smaller impact on sleep. For this group, the average sleep score fell by only 1.4 points in the week before their period, compared with 3.4 points in natural cycles. Nighttime heart rate rose by 1.0 bpm rather than 2.8 bpm, and the drop in heart rate variability almost disappeared. This supports the role of natural cycle hormones in premenstrual sleep disruption, as most hormonal methods smooth out the natural rise and fall of progesterone and estrogen.
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