Be aware of the potential health risks of rotating work.
One of the defining features of Emergency Departments is that they are always open: 24/7/365. However, research shows that providing care at all hours of the day and night comes with a cost. The physicians and staff who give up their sleep and their circadian rhythms may also be sacrificing their health.
While there are no large-scale, randomized, controlled trials of shift work that definitively identify all the potential risks, there a number of large observational studies that have attempted to tease out the health risks associated with either rotating shift work or night shift work. In this Rx Pad, we will discuss what is known about the health risks of rotating or night shift work, which, for simplicity, we will refer to as “shift work.”
Acute Respiratory Illness
Do you feel like you are always sick or coming down with something? Shift work is associated with a 20% increase in the risk of influenza-like illness or acute respiratory infections (odds ratio of 1.2, CI 1.01-1.43).
Diabetes
A number of studies have looked at the risk of developing specific chronic diseases due to shift work. In a large study of US cohorts of female nurses that enrolled 143,410 participants and had 22-24 years of follow up, Shan et al found a hazard ratio of 1.31 (CI 1.18-1.44) for developing type two diabetes for every five-year increment of rotating shift work.[1]
Shift work was defined as at least three night shifts per month, in addition to other day or evening shifts. They also found a risk of 2.3 (CI 1.88-2.83) for each unhealthy lifestyle factor that the subject had. They defined these as currently smoking, low quality diet, physical activity of less than 30 minutes per day and BMI of 25 or more. Interestingly, the combination of an unhealthy lifestyle factor with shift work increased the risk of developing diabetes by more than the expected combination of the two risks, with an excess added risk of 0.2 compared with the expected risk from combining the two risk factors (p<0.001).
Cardiovascular Disease
Shift work confers higher risks of hypertension and cardiovascular-related morbidity and mortality. A systematic review and meta-analysis of nine cohort studies found the odds ratio of developing hypertension was 1.34 (CI 1.08-1.67) for rotating shift workers.[2] Another study found a relative risk of morbidity from coronary heart disease of 1.26 (CI 1.01-1.43), as well as a relative risk of mortality from cardiovascular disease of 1.22 (CI 1.09-1.37).[3] They also studied a dose response, and found for every five years of exposure to night shift work, there was a 7.1% increase in risk of cardiovascular events.
Cancer
There may be a higher risk of certain cancers among night shift workers. In men, shift work carries a hazard ratio of 2.29 (CI 1.43-3.67) for development of prostate cancer over a 10-year study. As with the other chronic diseases above, the hazard ratio increased with the years employed in shift work.[4] Other studies have looked at the risk of breast cancer with shift work and found either no effect or an extremely small effect.[5]
Dementia
Finally, shift work appears to also increase the risk of dementia. A European study of two population-based cohorts found an overall hazard ratio for every having done shift work of 1.36 (CI1.15-1.60).[6]
A Scandinavian study of a Danish registry of 28,731 female nurses recruited in the mid- to late-90s examined cause-specific and all-cause mortality with shift work, and compared day, evening, night and rotating shift workers. They found that night shift and evening shift workers had a hazard ratio of 1.26 (CI 1.11-1.49) and 1.29 (CI1.11-1.49) respectively for all-cause mortality, compared with day shift workers. Consistent with the other studies listed above, they found night shift workers had higher rates of cardiovascular disease (HR 1.71, CI 1.09-2.69) and diabetes (HR12, CI 3.17-45.2), but no increased risk of cancer-related mortality. Though the numbers of deaths related to dementia were low, they did find a statistically significant increase in risk for evening (HR 4.28, CI 1.62-11.3) and rotating shift workers (HR 5.9, CI 2.35-12.3).[7]
Putting it All Together
While the hazard ratios for all of the conferred risks are relatively small, they become much more significant with the recognition that about 6% of working adults in the US work in shift work.8 Many industries other than health care employ shift workers. Therefore on a public health scale, these small or modest risks can have large effects. A review of the social and economic burden of shift work summarized the available literature, noting increased risks attributed to shift work of: hyperlipidemia, hypertension, heart disease, metabolic syndrome, peptic ulcers, gastrointestinal problems, certain cancers, pregnancy or fertility problems, higher BMI, anxiety, depression and fatigue.[8]
Should you keep your day job?
In most hospitals, emergency physicians cannot choose to only work day shifts, so instead, we should try to work to mitigate the negative health risks of night shifts or provide additional support for shift workers. Unfortunately, there is little the data can recommend, other than reducing one’s exposure to night shifts. From studies such as Shan et al, which found an excess additive effect when combining shift work with negative lifestyle factors, we can infer that if avoiding those negative lifestyle factors, we will at least avoid some of the added risk of chronic diseases that are compounded by shift work.
There are some studies on how to reduce fatigue and errors due to sleep-deprivation during night shifts. A Cochrane review looked at 17 different studies of interventions such as bright light exposure, napping and other sleep or exercise-related interventions on sleepiness in shift workers, but did not find any approach that was definitively beneficial. There is even a Cochrane review confirming what all emergency physicians know: caffeine can help improve cognitive function and performance in shift workers, a finding also borne out by the authors’ personal experience.[9]
Conclusions
The burden of shift-work for individuals and as a health-care system is significant. Night shifts take a major toll acutely, for most people, with feelings of fatigue and difficulty concentrating. But they also take a chronic toll on the shift worker. In many hospitals, physicians working night shifts are paid more, or receive some other benefits in order to incentivize night shifts. Some people prefer night shifts for the relative autonomy they provide and the camaraderie among night-workers. Other individuals work nights to facilitate family schedules packed with children’s activities, childcare, home-duties and school.
While we cannot close emergency departments at night in order to ensure all staff get adequate, regular shut-eye, shift-workers should understand the risks that they are taking on. We may be able to reduce or at least mitigate our higher risk of some of the chronic diseases, by minimizing other modifiable risk factors such as diet and exercise. Beyond that, more research is needed on how we can reduce the health risks associated with shift work. Until then, venti macchiatos and healthy lifestyles may be our best lines of defense.
References
- Loef B, van Baarle D, van der Beek AJ, Sanders EAM, Bruijning-Verhagen P, Proper KI. Shift Work and Respiratory Infections in Health-Care Workers. Am J Epidemiol. November 2018. doi:10.1093/aje/kwy258.
- Shan Z, Li Y, Zong G, et al. Rotating night shift work and adherence to unhealthy lifestyle in predicting risk of type 2 diabetes: results from two large US cohorts of female nurses. BMJ. 2018;363:k4641. http://www.ncbi.nlm.nih.gov/pubmed/30464025. Accessed January 10, 2019.
- Manohar S, Thongprayoon C, Cheungpasitporn W, Mao MA, Herrmann SM. Associations of rotational shift work and night shift status with hypertension. J Hypertens. 2017;35(10):1929-1937. doi:10.1097/HJH.0000000000001442.
- Torquati L, Mielke GI, Brown WJ, Kolbe-Alexander T. Shift work and the risk of cardiovascular disease. A systematic review and meta-analysis including dose-response relationship. Scand J Work Environ Health. 2018;44(3):229-238. doi:10.5271/sjweh.3700.
- Behrens T, Rabstein S, Wichert K, et al. Shift work and the incidence of prostate cancer: a 10-year follow-up of a German population-based cohort study. Scand J Work Environ Health. 2017;43(6):560-568. doi:10.5271/sjweh.3666.
- Travis RC, Balkwill A, Fensom GK, et al. Night Shift Work and Breast Cancer Incidence: Three Prospective Studies and Meta-analysis of Published Studies. J Natl Cancer Inst. 2016;108(12):djw169. doi:10.1093/jnci/djw169.
- Bokenberger K, Sjölander A, Dahl Aslan AK, Karlsson IK, Åkerstedt T, Pedersen NL. Shift work and risk of incident dementia: a study of two population-based cohorts. Eur J Epidemiol. 2018;33(10):977-987. doi:10.1007/s10654-018-0430-8.
- Jørgensen JT, Karlsen S, Stayner L, Andersen J, Andersen ZJ. Shift work and overall and cause-specific mortality in the Danish nurse cohort. Scand J Work Environ Health. 2017;43(2):117-126. doi:10.5271/sjweh.3612.
- Culpepper L. The social and economic burden of shift-work disorder. J Fam Pract. 2010;59(1 Suppl):S3-S11. http://www.ncbi.nlm.nih.gov/pubmed/20074508. Accessed December 10, 2018.
- Ker K, Edwards PJ, Felix LM, Blackhall K, Roberts I. Caffeine for the prevention of injuries and errors in shift workers. Cochrane Database Syst Rev. May 2010. doi:10.1002/14651858.CD008508.
