A study published in NPJ Digital Medicine by researchers at Stanford University and WHOOP indicates that less sleep may lead to less predictable menstrual cycles. The research involved 2,596 women aged 18 to 50 who were neither pregnant nor using hormonal contraceptives and were not in peri/menopause. The findings reveal that reduced sleep duration correlates with greater variability in menstrual cycle lengths.

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Participants wore a wrist device that recorded sleep data and metrics like resting heart rate variability, breathing rate, skin temperature, and blood oxygen saturation, accumulating approximately 1.2 million days of data over 42,759 menstrual cycles. Dr. Lourdes DelRosso, director of Inspire Health Sleep Medicine and a professor at UCSF, noted, "This study shows an important association between lack of sleep and period regularity," while emphasizing that the study indicates correlation, not causation. Dr. DelRosso cautioned that various factors, including social stressors and physical discomfort, might influence the results.

The study found that women sleeping an average of six hours experienced more menstrual cycles that deviated by three or more days from their typical patterns, in comparison to those who slept eight hours. Additionally, cycle lengths were more consistent among those averaging over 7.3 hours of sleep. The American Academy of Sleep Medicine recommends that adults get at least seven hours of sleep, while children and adolescents need even more, generally between eight to ten hours.

Dr. DelRosso highlighted the significance of sleep for hormone regulation during the early stages of menstruation, stressing that parents should be aware of the importance of adequate sleep for their daughters who begin menstruating around age 10 or 11. To improve sleep, she recommends maintaining consistent sleep practices, including regular bedtimes and wake-up times, and minimizing exposure to electronics and bright light before sleep.

The study also identified a weak association between sleep duration and the actual length of menstrual cycles.