Night shifts, hormones and women’s health: what does the science say?

Hospitals, care homes and emergency services never sleep—and neither do many of the women who keep them running. 

Millions of healthcare professionals work evenings, nights and rotating shifts every year. While shift work is essential, research has shown that regularly working at night can affect the body’s natural circadian rhythm, influencing sleep, mood and several hormone-regulated processes. 

That doesn’t mean everyone who works nights will experience health problems, but understanding the potential effects can help you make informed choices about your wellbeing. 

Your body’s internal clock 

The body operates on a roughly 24-hour cycle known as the circadian rhythm. 

This internal clock helps regulate sleep and wakefulness, body temperature, digestion, hormone release and metabolism. Exposure to daylight plays a key role in keeping this rhythm aligned. 

Night shifts require people to stay awake when the body naturally expects sleep, and to sleep during daylight hours when the brain is naturally more alert. This mismatch can make restorative sleep more difficult to achieve. 

Why sleep quality matters 

After a night shift, many people sleep for fewer hours than they would after a daytime schedule. Daytime sleep is often interrupted by light, household noise, family responsibilities or simply because the body’s biological clock promotes wakefulness during the day. 

Over time, poor-quality sleep can affect: 

• Concentration. 

• Memory. 

• Mood. 

• Physical recovery. 

• Immune function. 

• Overall wellbeing. 

For healthcare workers making important clinical decisions, protecting sleep whenever possible is especially important. 

What about hormones? 

Hormones are closely linked with sleep and the circadian rhythm. 

Researchers continue to study how long-term night shift work may influence hormone-regulated systems, including reproductive health. Current evidence suggests that disrupted sleep and circadian rhythms may affect hormonal balance, but the relationship is complex and varies between individuals. 

Menstrual cycles 

Some studies have found an association between shift work and changes in menstrual patterns, including irregular cycles in some women. 

However, not everyone who works nights experiences these changes, and many other factors—including stress, age, body weight and underlying medical conditions—can also influence menstrual health. 

If your periods become significantly irregular, unusually heavy or stop unexpectedly (outside of pregnancy or menopause), it’s worth discussing this with your GP. 

Fertility 

Research examining shift work and fertility has produced mixed results. 

Some studies suggest there may be an association between prolonged night shift work and reproductive health, while others have found little or no significant effect. At present, there is no clear evidence that night shifts alone cause infertility. 

If you are trying to conceive and have concerns about your reproductive health, speak with your GP or fertility specialist, who can provide advice based on your individual circumstances. 

Mood and mental wellbeing 

Anyone who has worked a run of night shifts knows how difficult it can be to feel your best after poor sleep. 

Sleep disruption can contribute to irritability, lower mood, increased stress and difficulty concentrating. These effects are not unique to healthcare workers, but they can feel more challenging in busy clinical environments where attention and communication are critical. 

Looking after your mental wellbeing is just as important as looking after your physical health. 

Practical ways to reduce the impact 

While shift work can’t always be avoided, small changes may help support your wellbeing: 

• Keep your bedroom as dark, cool and quiet as possible using blackout curtains or an eye mask. 

• Wear sunglasses on the journey home if bright morning light makes it harder to fall asleep. 

• Maintain a regular sleep routine where your shift pattern allows. 

• Limit caffeine towards the end of your shift. 

• Stay physically active on your days off. 

• Eat balanced meals and stay well hydrated. 

• Speak with your manager if fatigue is becoming a safety concern. 

• Seek medical advice if persistent sleep problems are affecting your health. 

Caring for yourself after caring for others 

Healthcare workers spend countless nights looking after patients when the rest of the world is asleep. 

Looking after your own sleep isn’t a luxury—it’s part of protecting your long-term health, your wellbeing and your ability to continue caring for others safely. 

Medical disclaimer 

This article is provided for general information, personal research and editorial opinion only. It is not intended to replace professional medical advice, diagnosis or treatment. Research into shift work and women’s health is ongoing, and individual experiences vary. If you have concerns about your menstrual cycle, fertility, sleep or mental wellbeing, speak with your GP or another qualified healthcare professional. If symptoms are severe or affecting your ability to work or function safely, seek medical advice promptly.