A good night’s rest isn’t a cure-all when you are trying to conceive. However, it turns out, regular healthy sleep cycles have an impact on your fertility health. The American Society for Reproductive Medicine’s (ASRM) flagship journal, Sterility and Fertility recently highlighted a meta-analysis of sleep studies. The goal of the meta-analysis was to understand the links between sleep and reproductive health.

Understanding the Challenges of Sleep Studies

The science of sleep is still relatively new and thus carries some challenges in obtaining data and managing the variables. To understand the limitations and the conclusion of the study, it helps to know some of the common challenges of studying sleep and fertility:

  1. There are wide ranges of sleep indicators to be quantified:
    –chronotypes (are you a night or morning person?)
    –type or cycle of sleep (like REM cycle, etc.)
    –sleep interruptions
    –irregularities (like shift work)
    –pathologies (like narcolepsy, insomnia, etc.) to be quantified.
  2. Devices that objectively quantify sleep (like polysomnography or actigraphy) are not easily accessible. Sleep studies in tightly controlled environments like dedicated sleep clinics are more uncommon. Therefore researchers rely more on subjective reporting tools (sleep journaling, self-assessments, etc.).
  3. There are tangled and multi-faceted relationships between sleep, fertility, and co-morbidities (such as diabetes, obesity, cardiovascular disease, mental health, etc.).
  4. Those tangled relationships are further complicated by the demographics of the patients who are most often included in sleep studies. (For example, shift workers, health care providers, and infertility patients).

Understanding the Reason Behind the Studies

We’ve known for many years that our sleep cycles follow what are known as circadian rhythms. Circadian rhythms are the internal processes that occur in the human body every 24 hours or so. Our bodies’ systems run via internal clocks if you will. Our circadian rhythms are responsible for heart function, brain function, and hormonal function. The biological timekeeper inside of us is subject to our environment, the light and dark cycles of day and night, and other variables that we can control. And many others that we cannot.

In early sleep science, researchers discovered that our circadian rhythms regulate sleep-wake cycles and hormone production and release. Melatonin is the hormone that regulates sleep. There are melatonin receptors throughout the human body – including in both the male and female reproductive organs. Previous studies have revealed that disruptions in the circadian cycles can disrupt hormone cycles as well. Studying sleep duration, chronotypes, night or shift work to understand the link between sleep and fertility health seems like a logical connection.

June is Men’s Health Month. Listen to Male Infertility 101 to learn more about what impacts a man’s fertility health.

Understanding the Conclusions

After examining more than 1,200 articles, the authors narrowed down the body of research studies to 33 high-quality articles for their review. From those 33 articles, the authors drew a few general conclusions that short or interrupted sleep (that is, less than 5 or 6 hours) may interfere in the following ways:

  • Increased risk of menstrual cycle irregularity
  • Abnormally short or long menstrual cycles
  • Decreased sperm quality (motility)
  • Decreased sperm count and volume
  • Increased difficulty in natural conception in both male and females
  • Potential for poorer IVF outcomes, as well as varying impacts at the different stages of the IVF process

Reviews of these articles also confirmed an association between irregular sleep cycles or night shift work schedules and some degree of fertility dysfunction.

Understanding the Limits of the Review

In addition to the limited availability of studies on the matter, reviewers also found the methods to evaluate sleep factors were quite varied. This makes it difficult to compare results. For example, some data was gleaned from subjective sources like self-assessments or limited questionnaires.

It’s also worth noting that shift work factors were not measured equally or accurately. The terms of frequency of night work, duration of a shift, or specific work details of the participants were not quantified.

Finally, because sleep is so integral to, and enmeshed with, a person’s quality of life, mental, and emotional health, there are many “confounding factors” that have not yet been adequately studied. Age and Body Mass Index are commonly factored into the research about sleep and fertility but other factors like depression or anxiety disorders and stress leave room for much more study.

Additional Research Is Needed

It’s clear that there is indeed a link (or several) between sleep and fertility health. Given the many variables that exist and the rapidly evolving nature of the science of sleep, it will be interesting to see how the research unfolds.

The authors conclude their review by stating,

Sleep could represent an original and innovative parameter to consider in the reproduction field… additional large-scale investigations are needed to elucidate how sleep and fertility are interrelated and how sleep could represent a useful modifiable target in infertility management.


Image Credits: Kenneth Lu; Gauthier DELECROIX - 郭天; Seniju