Lets start with a statistic; 6.1 million American women have difficulty getting pregnant and struggle with their infertility. This is shocking and is on the rise.
Many men also have infertility issues linked to disrupted circadian rhythms.
Sleep dysfunction, in part brought about by poor light hygiene, is leading to an increase in infertility rates across the world. In this article I have taken the latest research on reproduction and circadian rhythms and presented it in several categories.
- Female Fertility
- Male Fertility
- Reproductive Health
- Pregnancy and Birth
A staggering 6.1 million American women struggle to get pregnant. Infertility is defined by the CDC as a period of 12 months or more of having unprotected sex without the result of conception. It appears from the literature that disruption to a woman’s circadian rhythm plays a huge role in fertility.
All hormones in our bodies are controlled by clock genes. These are genes that are influenced by environmental factors that either entrain or disrupt their natural rhythms. To have correctly oscillating clock genes we must manage light correctly, eat at specific times of the day and also exercise at the right time. All these factors when done correctly lead to a properly functioning circadian rhythm. For example, sunlight during the day, blocking artificial blue and green light after sunset, eating your largest meal between 9am and 2pm and performing cardiovascular exercise in the morning will also lead to correctly functioning and healthy circadian rhythms.
Circadian rhythms and “clock gene” expression are involved in successful reproductive cycles, mating, and pregnancy. Alterations or disruptions of biological rhythms are linked to significant disruptions in reproductive function.
These impairments include altered hormonal secretion patterns, reduced conception rates and increased miscarriage rates.
One hormone that plays a huge role in the reproductive system of women is Oestrogen (Estrogen). Oestrogen has been known to modify clock genes in the reproductive system.
If your Oestrogen levels become too high, too low or run on a mismatched circadian oscillation they may impact the clock genes in the reproductive system which can lead to issues such as Polycystic Ovary Syndrome (PCOS), which is one of the leading causes of infertility in women.
Studies have shown that Melatonin plays an important role in egg fertilisation and embryo viability.
Disrupted circadian rhythms and misaligned melatonin cycles make it more difficult to conceive.
Melatonin is a hormone produced in the pineal gland in the absence of blue and green light after sunset. To increase fertility rates in women it would therefore make sense to try to produce as much Melatonin as you can, natural after sunset. Wearing blue light blocking glasses that block all blue and green light between 400-550nm would be a great starting point.
Prolactin is another hormone that has been scientifically proven to influence fertility rates in women. Prolactin literally means “to produce milk” and is an essential part of the reproductive rhythms in women.
Prolactin influences fertility in woman and if their clock genes are disrupted they can then increase the risk of PCOS and lack of normal ovulation.
As with most other hormones linked to reproductive health, Prolactin is secreted at higher levels during sleep and is suppressed by inadequate sleep, in part caused by exposure to blue and green light after sunset.
A disrupted circadian rhythm is associated with disturbances in menstrual function. Female shift workers compared to non-shift workers are more likely to report menstrual irregularity and longer menstrual cycles.
Shift work is one of the major causes of disrupted circadian rhythms as we are exposing ourselves to artificial blue and green light when we should be sleeping. Shift work has been shown to increase all-cause mortality and dramatically impact fertility rates in men and women.
As with women, Melatonin has been shown to control reproductive hormones in men.
Disrupted circadian rhythms in men has been shown to decrease sperm quality and quantity.
A disrupted circadian rhythm brought about through poor light management can either make men sleep too much or not enough. Both very long and short sleep durations have been associated with male fertility problems.
Men who sleep too much or not enough are 42% less likely to conceive with their partner.
Poor quality and lack of sleep also leads to a reduction of testicle size in men. A reduced testicle size can make it more difficult to produce higher volumes of sperm.
The hormone involved in male fertility rates is Testosterone. Low levels of Testosterone have been shown to produce lower sperm counts. Two factors that have the biggest impact on testosterone is chronic stress (disrupted cortisol clock) and poor sleep (disrupted master clock).
Improving sleep quality for men is therefore very important in increasing fertility. Men need to address their light environment after sunset in order to potentially increase sperm count and quality.
Sperm production also has its own circadian rhythm. In a recent academic study, semen collected before 7:30am had a much higher sperm count and concentration when compared with semen collected much later in the day.
The study also showed that sperm collected before 7:30am had a higher proportion of healthy, normal sperm compared with later in the day.
Seasons also affect the quality and quantity of sperm. This seasonal circadian effect shows that sperm count increases throughout spring and decreases during the summer.
Anti-Sperm Antibody (ASA)
Anti-Sperm Antibody (ASA) has been shown to negatively impact fertility in men. This study showed that men who fall asleep past midnight had higher ASA levels than those who went to bed between 10pm and midnight.
The group that went to sleep post-midnight also recorded lower sperm counts and lower rates of sperm survival than the early to bed group.
Having a properly functioning circadian rhythm will allow for men to go to sleep at earlier times and wake at earlier times. It is very clear in the literature that early risers will have better sperm counts and be awake to take advantage of this with their partners. Those who go to bed earlier will produce better quality sperm thus increasing fertility and the likelihood of successful conception.
Reproductive health is not just important for fertility but also for the longevity of the Mother and Father.
Melatonin is produced in the ovary and in the placenta, where is protects against cellular damage arising from oxidative stress. The placenta is particularly susceptible to free radical generation so Melatonin secreted at this junction is essential for maintaining optimal placental health.
Poor Melatonin levels brought about by disrupted light/dark cycles will leave women more susceptible to ovarian cancer.
There is also substantial evidence that circadian disruption increases the risk of breast cancer in women due to altered light exposure and reduced melatonin secretion.
Poor quality and low duration of sleep has been shown in this study to increase rates of prostate cancer in men.
Men, as well as women, need to properly manage their light environment and circadian health in order to improve the chances of conception and to also look after their own reproductive health.
Pregnancy and Birth
I have already discussed that Melatonin is produced in the ovaries and placenta. Without adequate Melatonin production at these sites it could lead to complications during pregnancy.
The Mother’s circadian rhythm programs the developing master clock of the foetus. Studies have shown that a disturbed maternal circadian rhythm has negative consequences for the maturing foetal clocks which could lead to psychological and behavioural problems in the newborn.
To promote delivery of the baby Melatonin must synergise with Oxytocin. This is why the majority of births happen at night when Melatonin is highest. It is essential that blue and green light is managed appropriately after dark to ensure the correct time of delivery and reduce the likelihood of any complications during and after birth.
I have already analysed the below study on an older bog but it makes sense to finish with it again on this article. A Mother’s circadian rhythm will impact the milk produced during and post-pregnancy.
Milk secreted in the daytime is highest in Cortisol, the hormone that is needed during the day to keep us awake. Milk secreted after sunset is highest in Melatonin and Tryptophan. Melatonin and Tryptophan (along with Serotonin – obtained from sunlight) assist in sleep.
The two points I would like to make on this study is firstly ensure you feed your baby breast milk at the time of day it was pumped. If you feed your baby day pumped breast milk after sunset you could disrupt their circadian rhythm as you will be given them high doses of Cortisol which may case an awakening response.
The opposite is true if you give them breast milk pumped after sunset, during the day. It will make them sleepy when they should be awake.
Secondly, it can be hypothesised that if the mother has a term carrying the baby with her own circadian rhythm disrupted, breast milk may also be altered at a hormonal level. It could be beneficial to maintain correct circadian health during pregnancy.
Disclaimer; This article is not intended as medical advice. It is solely presenting results from certain academic studies for my own personal review. Do not attempt any of the advice in this article without consulting a qualified medical practitioner.