Shift work means businesses and organizations can be productive 24 hours a day. With the development of artificial lighting, manufacturing, service and retail sectors have used shift work to increase productivity and profitability. It also allows for the provision of continous healthcare and emergency services.
I found out that the Cold Storage in Holland Village across the road from our clinic pays a monthly rent that is in excess of $200,000 a month. That's probably one of the reasons why they are open 24 hours. To maximise what they already pay for rental.
So I was not surprised to read that shift work, in particular night work is associated with chronic musculoskeletal pain (Matre et al, 2021). The mentioned study had 23,223 subjects which was adjusted for sex, age and education reviewed significant associations between shift work and chronic musculoskeletal pain and chronic pain sites.
It is estimated that 20 percent of the workforce are now shift workers, with 25 to 30 percent of those working nights.
Evidence now shows that working when you're supposed to sleep and rest disrupts your normal physiology. Growing evidence points to the disruption of the circadian clock caused by being awake or active at nigt when we're supposed to sleep.
All living species since evolution, from bacteria, plants to animals have acquired a circadian clock to optimize body processes in an environment that changes throughout the day. We are rhythmically organized to anticipate these daily changes.
Our immune system, muscular system and cognitive performances are higher in the day when the body is also storing nutrients from food. The functions decrease at night when the body starts to use he stored nutrients during this period of fasting.
Just like a conductor of an orchestra, our central clock in the brain synchronises all the circadian clocks along with environmental light. If these clocks get input from other sources like food or other light sources at night, this synchrony is lost.
Shift work simulation has been shown to affect the immune system. This contributes a higher risk of infection among shift workers, notably Covid-19.
Circadian disruption is also associated with disturbance of our the autonomous nervous system which controls breathing and our heart beat. This affects the connection between the brain and its surrounding tissues and their proper function.
This contributes globally to weight gain, Type II diabetes, increased blood pressure, compromised immune response and chronic musculoskeletal pain. This lost synchronicity also leads to a increased incidence of breast cancer, faster tumour growth and also exacerbates Alzheimer's disease. This is seen even in cases of low intensity light in the bedroom coming from a TV screen.
What can we do about it? The first step should be to limit rotating shift work as much as possible. It is somewhat possible to adapt to work at the "wrong" time but impossible to adapt to schedules that constantly change.
Some studies showed that bright light increases alertness during the night and helps adaptation to night work by shifting the circadian clock. However, long term impact on health is still unknown.
Controlling and limiting the time during which we eat (e.g. 10 hours during the day and not eating overnight) appears to be beneficial for heart and metabolic health (Sutton et al, 2018). This may be compatible with shift work.
There is probably no optimal solution for this unless we limit shift work to just essential hospital services. This may then help reverse the global trend towards a 24 hour society to decrease shift work for better health.
Are we able to take that huge step? Especially when most countries are opening up again after Covid-19.
References
Dun A, Zhao X, Jin X et al (2020). Association Between Night-shift Work And Cancer Risk: Updated Sysyematic Review And Meta-analysis. Front Oncol. 10:1580. DOI: 10.3389/fonc.2020.010006
Manouchehri E, Taghipour A, Ghavami V et al (2021). Might-shift Work Duration And Breast Cancer Risk: An Updated Systematic Review And Meta-analysis. BMC Women's Health. 21: 8. DOI: 10.1186/s12905-021-01233-4
Matre D, Christensen JO, Mork PJ (2021). Shift Work, Inflammation And Musculoskeletal Pain -The Hunt Study. Occu Med (Lond). 71(9): 422-427. DOI: 10.1093/occmed/kqab133.
Sutton EF, Beyi R, Early KS (2018). Early Time-restricted Feeding Improves Insulin Sensitivity, Blood Pressure, And Oxidative Stress Even Without Weight Loss In Men With Prediabetes. Cell Metab. 27(8): 1212-1221. DOI: 10.1016/j.cmet.2018.04.0
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