Night work, on-call duty, and Sunday work are various types of shift work.

ANSES (the French Agency for Food, Environmental and Occupational Health & Safety) published a report in 2016 on night work¹. It identified the proven effects of night work on the quality and quantity of sleep, on drowsiness and on waist circumference associated with signs of poorer vascular health.

Other effects on physical and mental health were likely, potentially exacerbated by difficulties in maintaining a social life.

But how can these risks be managed? Several factors need to be taken into account: circadian rhythm, amount of sleep, and social interactions.

Circadian rhythm (the internal clock)

As you may know, our bodies function like a biological clock. Hormonal changes occur throughout the day, causing changes in our behavior and how our bodies function. An obvious example is the secretion of melatonin, the sleep hormone that controls at least two things: body temperature and the sleep-wake cycle².

This secretion of melatonin is regulated by exposure to light, which would explain why many blind people have sleep disorders².

This is why you have heard about the risks of blue light for sleep and may have seen apps on your phone to reduce it, or even glasses with blue light filters to prevent our smartphones from delaying our melatonin secretion and therefore our bedtime.

Make no mistake, it is light in general that affects our biological rhythm³. There are reasons to believe that blue light may be the component of light that most affects sleep, but blue light filters are far from proven⁴, so until we have more practical information, it may not be worth worrying about.

Why talk about the internal clock? Well, it's simple! Exposure to light is one of the strategies that help manage shift work disorders: A bowl of intense light in situations where you are supposed to be awake and alert, and much dimmer light at times when you are supposed to be close to sleep, are strategies that could be effective in improving sleep and reducing sleepiness in people working shift work⁵. If you work at night, for example, even artificial light will help you create the alertness you need to perform well at work and at home, while reducing the brightness by closing the shutters will help you fall asleep more easily.

Regulating your internal clock may have other benefits, as it affects obesity, mental health, and the health of the nervous system, heart, and arteries⁶.

The amount of sleep

Just as it probably came as no surprise to you that shift work can trigger sleep disorders, you probably won't be surprised to read that sleep is good for your health.

To be precise, the National Sleep Foundation has established a range of recommended sleep schedules⁷ based on your age:

But what can you do to improve this, apart from managing your exposure to light as mentioned earlier? There are what are known as Cognitive Behavioral Therapies for Insomnia, which may be effective in improving various aspects of your sleep⁵.

What are they? CBT-i generally consists of three main elements:

• - Sleep hygiene advice: on the environment and substance use
• - Stimulus control: Making your bed a stimulus for sleep
• - Sleep restriction: deliberately restricting your sleep time in certain circumstances so that you are exhausted and fall asleep straight away when the time is right, to avoid spending too much time in bed without sleeping.

Psychologists are the most effective practitioners of CBT for insomnia, and it is now reimbursed by social security under certain conditions.

However, if you are unable to improve your sleep, there is always the possibility of compensating for it. In fact, some of the effects of sleep deprivation on our health can be attributed to low-grade inflammation, i.e., molecules that promote inflammation circulating in the blood⁸. And that's good news, because physical activity plays a key role in this⁹. To give you an example, we know that people with sleep disorders tend to experience more pain¹⁰ and that improving sleep with iCBT can improve pain¹¹.

And yet, when we put people with pain and sleep disorders on an exercise program, their pain improves. However, adding CBT-i to the exercise program, although it improves sleep, does not further improve pain¹².

This is interesting because it opens up a range of possibilities for good health.

Social interactions

It may not seem obvious, but social interactions appear to be essential to good health. Of course, you should keep in mind that an isolated person does not necessarily have good mental health, but even physically, social interactions keep us in shape. To give you an example, all-cause mortality was associated with social isolation.

This can be explained in several ways, from changes in our stress response system to simply poorer lifestyles: alcohol consumption, smoking, less physical activity, not taking medication... a kind of letting go.

So, if you have the opportunity, don't neglect social interaction; take time to see a loved one every week. Call people from time to time, and if you feel you don't have enough people around you, why not join a hobby or exercise club to meet new people?

Summary

When you work irregular hours, there are a few options to help you stay healthier and live better:

• - Manage your biological clock through exposure to or avoidance of light.
• - Improve sleep quality with CBT-i, which will help you make your bed a place for sleeping.
• - Exercise for its compensatory effects on your body chemistry if you are sleep deprived.
• - Remember to maintain social interactions.

Sources :

1. 1. Expertise collective ANSES. Évaluation des risques sanitaires liés au travail de nuit. Preprint at https://www.anses.fr/fr/system/files/AP2011SA0088Ra.pdf.
2. 2. Zisapel, N. New perspectives on the role of melatonin in human sleep, circadian rhythms and their regulation: Melatonin in human sleep and circadian rhythms. Br. J. Pharmacol. 175, 3190–3199 (2018).
3. 3. Cho, Y. et al. Effects of artificial light at night on human health: A literature review of observational and experimental studies applied to exposure assessment. Chronobiol. Int. 32, 1294–1310 (2015).
4. 4. Singh, S. et al. Blue-light filtering spectacle lenses for visual performance, sleep, and macular health in adults. Cochrane Database Syst. Rev. 8, CD013244 (2023).
5. 5. Jeon, B. M., Kim, S. H. & Shin, S. H. Effectiveness of sleep interventions for rotating night shift workers: a systematic review and meta-analysis. Front. Public Health 11, 1187382 (2023).
6. 6. Fishbein, A. B., Knutson, K. L. & Zee, P. C. Circadian disruption and human health. J. Clin. Invest. 131, e148286 (2021).
7. 7. Hirshkowitz, M. et al. National Sleep Foundation’s updated sleep duration recommendations: final report. Sleep Health 1, 233–243 (2015).
8. 8. Irwin, M. R., Olmstead, R. & Carroll, J. E. Sleep Disturbance, Sleep Duration, and Inflammation: A Systematic Review and Meta-Analysis of Cohort Studies and Experimental Sleep Deprivation. Biol. Psychiatry 80, 40–52 (2016).
9. 9. Metsios, G. S., Moe, R. H. & Kitas, G. D. Exercise and inflammation. Best Pract. Res. Clin. Rheumatol. 34, 101504 (2020).
10. 10. Runge, N. et al. The bidirectional relationship between sleep problems and chronic musculoskeletal pain: a systematic review with meta-analysis. Pain 10.1097/j.pain.0000000000003279 (2022).
11. 11. Selvanathan, J. et al. Cognitive behavioral therapy for insomnia in patients with chronic pain - A systematic review and meta-analysis of randomized controlled trials. Sleep Med. Rev. 60, 101460 (2021).
12. 12. Malfliet, A. et al. Cognitive behavioral therapy for insomnia in pain management for nonspecific chronic spinal pain. JAMA Netw. Open 7, e2425856 (2024).
13. 13. Wang, F. et al. A systematic review and meta-analysis of 90 cohort studies of social isolation, loneliness and mortality. Nat. Hum. Behav. 7, 1307–1319 (2023).