If you spend much of the night tossing and turning, you're not alone. Between 50-70 million Americans suffer from chronic sleep problems, according to estimates from the Institute of Medicine.
Women tend to fare worse than men in the quest for a good night of ZZZs. Roughly 1 in 4 women report trouble staying asleep and other symptoms of insomnia. While researchers suggest fluctuations in reproductive hormones may explain women’s fitful sleep (1), we can't gloss over the sleep-zapping effects of pre-dawn wake-up calls from kiddos, erratic work and school schedules, and the rest of life's demands.
Since experts say 7-9 hours of sleep nightly is good for our health, it's no surprise that missing out on much-needed rest can mess with your menstrual cycle — and even your fertility.
Here, we unpack the latest reproductive science on sleep in women and explain how too much or too little sleep may make men less fertile.
U.S. labor statistics show nearly 15 million Americans work night shifts or some type of irregular schedule. Clocking in at odd hours or at night may lead to menstrual cycles that are shorter, longer, or irregular, per research published in the American Journal of Epidemiology that tracked the cycles of 74,436 nurses over time (2). The chief takeaway: Menstruation is "adversely affected by rotating shift work."
Why? The research team theorized that working rotating night shifts exposed the nurses to light at night, when their bodies least expected it. This schedule disrupted the nurses' internal circadian rhythm, which in turn changed their physiological functions in some fashion that affected their periods.
A study published this month in Fertility and Sterility explored these very questions. The researchers tracked 6,873 women for 6 months as they tried to conceive and found no sign that shift work made the women less fertile (3). However, the authors did note a slight link between getting fewer than 6 hours of sleep nightly and reductions in fertility.
Previous studies have also probed the potential link between problematic sleep and fertility, although the research was limited to women at infertility clinics, rather than a broad sample of women. One study showed that women with non-apnea sleep disorders had a higher risk of developing female infertility (4), while another found that fitful sleep was "significantly associated" with a diminished ovarian reserve (5).
The number of hours spent sleeping also affects male fertility, according to a recent paper in Fertility and Sterility (6). By tracking 1,176 men and their partners during a 6-month period as they tried to get pregnant, researchers found when men got fewer than 6 hours of sleep, it affected the couples' rates of conception. The effect was true even among men who'd already had children, suggesting sleep deprivation, which is common in the early years of parenting, may play a role.
Earlier research also linked sleep problems withand sperm count and quality. A paper published in The American Journal of Epidemiology reported lower sperm counts, less sperm concentration, and fewer healthy sperm among men with sleep disturbances (7). Sleep disturbances were defined as "sleeping less than 4 hours or waking frequently at night."
Meanwhile, a study in the journal Sleep suggested too few ZZZs and over-sleeping may harm sperm count and volume (8). Sleeping more than 9 hours was associated with a 21.5% reduction in sperm volume and 39.4% decline in sperm count, while sleeping fewer than 6.5 hours nightly was linked to a 4.6% drop in sperm volume and a 25.7% slide in sperm count.
A sleepless night here and there is nothing to fret about (apart from feeling like a zombie the next day). But if insomnia is becoming the norm, try a few hacks to your bedtime routine. Snooze notifications on your phone, read a physical book before turning in, or listen to a calming app to get you in the right frame of mind for a good night's sleep. For more tips, click here.
Bear in mind, sleep problems also affect your basal body temperature (BBT) because you need at least three consecutive hours of sleep for an accurate BBT reading. If you're curious how to mark your temp after a sleepless night, read this post.