Long Term Effect of Working the Night Shift

Written by Sabine Downer

It is easy to forget about the 15-million night shift workers that staff our hospitals, police and security, gas stations, restaurants, and manufacturing facilities [1]. These workers play an essential role in keeping us safe, healthy, and helping companies be more profitable. However, it has long been suspected that there are long term health effects of working the night shift. While there is little doubt that fatigue is a common issue for overnight worker, there are other concerns to also be aware of.

Circadian rhythms are 24-hour cycles that run in the background of our daily lives. These biological functions are part of what makes up the body’s internal clock. Long term night shift work disrupts these rhythms, and in turn disrupts our body’s natural functions.

A 2018 study by Yuan, et al. found that female long term night shift workers had significantly higher cancer risks [6]. Breast cancer, digestive system cancer, lung cancer, and skin cancer risks increased 3.3% for every 5-years of night shift work performed in the women they studied. Further evidence by Papantoniou, et al. in their own 2018 study explains further and also suspects an increased risk of colon cancer, saying [2]:

“Circadian disruption, sleep deprivation, light induced suppression of melatonin, and lifestyle changes are important mechanisms that have been suggested to explain the possible link between shift work and colorectal cancer risk. Disruption of the circadian clock may lead to deregulation of cell proliferation and mistiming of basic cell functions, such as DNA damage repair.”

In addition to increased risks of cancer, long term night shift work may also increase the risk of type 2 diabetes and cardiovascular disease [3, 5]. These risks are likewise attributed to circadian disruption and DNA damage. Permanent night shift workers have also demonstrated a 29% increase in obesity [4]. While lifestyle, genetics, and environment can also influence these conditions, researchers widely agree that long term night shift work increases chances of experiencing a variety of serious adverse health effects.

With 20% to 30% of North Americans and Europeans involved in shift work, it is important for workers to be aware of these increased risks so they can take precautions like more frequent cancer screenings or encouraging employers to rotate night shift workers to reduce long-term impacts.



  1. Price M. The risks of night work. Published 2011. Accessed May 18, 2021.,the%20Bureau%20of%20Labor%20Statistics.
  2. ‌Papantoniou K, Devore EE, Massa J, et al. Rotating night shift work and colorectal cancer risk in the nurses’ health studies. International Journal of Cancer. 2018;143(11):2709-2717. doi:10.1002/ijc.31655 Accessed May 18, 2021.
  3. Kervezee L, Cuesta M, Cermakian N, Boivin DB. Simulated night shift work induces circadian misalignment of the human peripheral blood mononuclear cell transcriptome. Proceedings of the National Academy of Sciences. 2018;115(21):5540-5545. doi:10.1073/pnas.1720719115 Accessed May 18, 2021.
  4. Sun M, Feng W, Wang F, et al. Meta-analysis on shift work and risks of specific obesity types. Obesity Reviews. 2017;19(1):28-40. doi:10.1111/obr.12621 Accessed May 18, 2021.
  5. Vetter C, Dashti HS, Lane JM, et al. Night Shift Work, Genetic Risk, and Type 2 Diabetes in the UK Biobank. Diabetes Care. 2018;41(4):762-769. doi:10.2337/dc17-1933 Accessed May 18, 2021.
  6. Yuan X, Zhu C, Wang M, Mo F, Du W, Ma X. Night Shift Work Increases the Risks of Multiple Primary Cancers in Women: A Systematic Review and Meta-analysis of 61 Articles. Cancer Epidemiology Biomarkers & Prevention. 2018;27(1):25-40. doi:10.1158/1055-9965.epi-17-0221 Accessed May 18, 2021.


Image: by dayamay from Pixabay

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Sabine Downer

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