Shift Work Could Be Making You Infertile, According to Science

We are always told how important a consistent sleep schedule is for our mental and physical well-being. But, in our 24-hour society, not everyone can afford this luxury. Research has highlighted the impact of shift work on human health, with effects on heart health and metabolism, including the increased risk of certain types of cancer. Jade Leanne, a 33-year-old flight attendant from Dorset in the U.K., has experienced this first-hand. Jade has worked as a flight attendant for 9 years, but it was only when she started working on long-haul flights that she began to notice something was wrong. "I first began tracking my cycles due to my erratic moods," Jade told Newsweek. "I felt overwhelmed with emotion, from teary to rather angry with no rhyme or reason."

Along with the mood swings, Jade noticed that her menstrual cycle had become less regular. "Having previously flown short haul I had no problems there," she said. "It was only when I began being awake during my normal sleep cycle and flying through different time zones that these problems came about." Jade was not alone in this: she said many of her colleagues have spoken openly about the impact of flying on their monthly cycles and fertility. In 2014, Jade and her partner began trying for their first baby. It was then that she realized the extent of the issue. "We didn't have our daughter until the last day of 2017," she said. "When we were first told I'd need to have IVF, I felt overwhelmed with shame. As if my body didn't work properly and something was wrong with me." Jade found no history of infertility issues in her family and her doctors were stumped as to what had caused her situation.

According to the World Health Organization, roughly 1 in 6 adults worldwide experience infertility. In the U.S., this is defined as not being able to get pregnant after at least one year of unprotected sex. Infertility in women can be caused by a range of biological conditions, including polycystic ovary syndrome (PCOS), hormonal imbalance, blocked fallopian tubes, and uterine disorders, to name but a few. However, fertility can also be impacted by lifestyle and environmental factors, including excessive exercise, extreme weight loss or gain, emotional stress, smoking, and lack of sleep. Marine Simonneaux, a Ph.D. researcher at the Institute of Cellular and Integrative Neuroscience, told Newsweek: "It is well established that disruption of circadian clocks has a negative impact on health. Change in light exposure and sleep debt due to rotating/shift work are associated with a higher risk of metabolic and cardiovascular diseases, cancers, and reproductive function disorders, [such as] irregular menstrual/ovarian cycles, increased risk of endometriosis, reduced mature oocyte yield, reduced fertility, and early onset menopause." Our bodies run on a series of internally driven cycles that rise and fall over the course of a 24-hour day. These rhythmic processes regulate our digestion, alertness, body temperature, and a range of other biological functions that fluctuate throughout the day and night. "Almost all physiological functions and behaviors are regulated by circadian clocks—sleep/wake cycle, hormone release, core body temperature," Simonneaux said. "The reproductive function is not an exception to this rule."

Our circadian cycles are kept in sync by a master clock that sits in the brain, which itself is reset every morning by sunlight, according to the National Institute of General Medical Sciences. However, changes to this daily exposure can throw our biological clocks off balance. In a recent study, Simonneaux and her colleagues subjected mice to shift work-like changes in light exposure. Within just four weeks, the hormonal surges that trigger ovulation had largely disappeared, reducing fertility in the study mice. The findings were announced at the European Congress of Endocrinology in Istanbul, Turkey, on May 16. "Our research shows that four weeks of chronic shift exposure impairs the transmission of light information from the master biological clock to the kisspeptin neurons, known to drive the timing of the pre-ovulatory luteinizing hormone surge," Simonneaux said. "Of course, it is important to be cautious in translating the data of animal studies to potential clinical applications. However, [...] regarding the reproductive system, many aspects are the same between women and mice. Female mice display an estrous cycle that can be compared to the menstrual cycle even though it lasts only four to five days."

Read more

• "I had a baby after IVF. There are challenges people don't talk about"
• Let's Change How We Talk About Motherhood and Pregnancy
• Early Warning Signs of Thyroid Problems and When You Should See a Doctor
• How Abortion Bans Could Make IVF Even More Expensive

It is important to note here that shift work does not only impact women's fertility. "Circadian disruption can also affect the men's reproductive function—for example, erectile dysfunction, deterioration of sperm quality parameters—leading to reduced fertility," Simonneaux said. The extent to which shiftwork impacts reproductive health will, of course, depend on the extent of circadian disruption. "Depending on the shift direction [i.e. whether the daylight cycle shifts backward or forwards...], the number of days between shifts, and the shift duration, the negative impacts on fertility will be more or less important and more or less reversible," Simonneaux said. "Furthermore, the effects could also differ regarding the period of life to which the women are exposed to shift work." More studies will be required to understand the mechanisms behind these effects and to investigate potential treatments for those who suffer from the consequences. On hearing about the study, Jade said that she was not surprised by its results. "I really do love what I do, [but] a career in flying is extremely strenuous on the body," she said. "I think I always knew deep down that flying was impacting my reproductive health."

Being diagnosed with infertility does not mean that you cannot have children, but it does make the road harder, more painful, and more expensive. However, after two rounds of IVF, Leanne and her partner managed to have a baby girl. "When we found out our second round of IVF worked, we were overwhelmed with happiness," she said. "I can't remember ever feeling as happy as in that moment." Jade, who goes by the name @themindsetmumma on Instagram, took to social media to share her story in the hopes that her experiences would provide inspiration and solace to others fighting similar battles. "I'd just like to take a moment to acknowledge and offer support to anyone who is currently struggling with infertility of any kind," she said. "I'm a passionate advocate for the demographic as I know first-hand just how intense it is. Infertility never leaves us." Is there a health issue that's worrying you? Do you have a question about infertility? Let us know via health@newsweek.com. We can ask experts for advice, and your story could be featured on Newsweek.