Night Shift Health Risks: Revisited

Abstract

A worker who consistently works night shifts over a substantial period of time faces a significant increase in overall risks to their physical and mental health. The principal ways in which night shift work serves as a detriment to the health of the worker are through circadian misalignment, sleep deprivation, and suppression of melatonin. Research findings indicate that these conditions place night shift workers at a greater risk for the development of compassion fatigue, cardiovascular disorders, cancer, diabetes, obesity, reproductive problems and pregnancy complications, gastrointestinal disorders, suppression of the immune system, hormonal imbalance, and depression. The time frame required for the development of these disorders varies depending on the particular health risk involved. Night shift workers are more likely to sleep at irregular intervals, fail to maintain adequate nutrition, neglect to exercise, and become sedentary. Night shift workers are also more likely to experience mental health problems involving social isolation, diminished exposure to family and social life, and a declining sense of well-being. Night shift workers should seek to compensate for these concerns by obtaining as much sleep as possible, maintaining a healthy diet and exercise regimen, and consulting regularly with a primary care provider.

Introduction: The Definition and Prevalence of Night Shift Work

Night shift workers are commonly defined at those employees whose regular working hours are normally scheduled outside of the conventional “nine to five” format. Such employees may consistently work a specific amount of hours while beginning and ending work at set intervals. An example would be someone who works the “graveyard shift” by coming in to work at midnight and leaving at 8 a.m. in the morning. A night shift worker may also work a rotating schedule and may work during different hours on particular days. The schedule of such a worker may even include some “normal” day shifts. Such an employee may work “nine to five” hours two days a week and be placed on an evening or late night shift on other days. Others may work two shifts back-to-back followed by additional time off.

It is unclear how many Americans work night shifts as defined above. However, it is estimated that the number of night-shift workers is somewhere between eight and fifteen million people in the United States. The occupations most likely to employ night shift workers include medical services, public transportation, emergency services, shipping, hospitality, food service, law enforcement, and military service. As service industries have come to dominate the American economy in recent decades, a greater number of workers in the United States are working night shifts. Therefore, potential health risks associated with night shift work have become an issue of increasing concern.

The Health Risks to Night Shift Workers: An Overview

The evidence indicates that both the psychological and physical health of a worker can be impaired by ongoing night shift work. Night shift workers are more likely to suffer from depression and a feeling of loneliness or isolation resulting from diminished contact with others. Night shift workers may also use alcohol or drugs more frequently or in higher quantities. An unconventional or irregular work schedule may diminish an individual’s interest or involvement in family, social, or recreational activities because of less available time for participation in such activities. Normal eating and sleeping habits may be interrupted and less attention may be given to matters of nutrition, avoiding weight gain, personal hygiene, and other issues of self-care.

The social relationships of a night shift worker may also suffer because of their abnormal work schedule. A person who keeps irregular hours will likely spend less time with their spouse, children, significant others, or friends. The relationship between a night shift worker and their spouse or significant other may suffer from a lack of physical or emotional intimacy and the other party to the relationship may begin to experience feelings of neglect. The relationship between a night shift worker and their children can also be negatively impacted in comparable ways. 

Outward symptoms experienced by night shift workers whose physical health has been compromised can include persistent feelings of fatigue or sickliness, depression, increased sensitivity to cold and other issues of adapting to the surrounding environment. Disorders relating to eating and digestion can emerge including nausea, diarrhea, and other matters of improper functioning of the bowels or digestive tract. Disruption of the sleep patterns of the night shift worker may make the overall attainment of sleep more problematical as the individual worker may find it more difficult to sleep even when sleep time is available. This, in turn, increases the impact of sleep deprivation.

Research Findings on the Health Risks to Night Shift Workers

It is clear enough that from the available research that working the night shift has consequences for an individual’s health, family life, and wellness. According to Mark R. Smith and Charmane I. Eastman of Rush University Medical Center in Chicago (2012), there are three mechanisms that may contribute to health, performance and safety problems associated with night-shift work.  These include (1) circadian misalignment between the internal circadian clock and activities such as work, sleep, and eating; (2) chronic, partial sleep deprivation; and (3) melatonin suppression by light at night (p. 1). The authors provided countermeasures and adaptation techniques on how to overcome the negative health risk for these workers. They provided explanations of how to manage risk, how to reset circadian misalignments, issues involving day-night sleep schedules, and the possibility of melatonin use to help manage the symptoms. These reviews were done by experts in their fields and are essential studies that provide useful information regarding the health risks for night shift workers and adaptation techniques that will help reduce or eliminate the associated risks.

Shift work that includes a nighttime rotation has become an unavoidable attribute of today's twenty-four-hour society. The related disruption of the human circadian time organization leads in the short-term to an array of jet-lag-like symptoms, and in the long-run it may contribute to weight gain/obesity, metabolic syndrome/type II diabetes, and cardiovascular disease (Haus, Smolensky 2012). It has also been suggested that night-shift work may increase the risk of an individual’s developing cancer. Women who work night shifts are at higher risk of developing breast cancer. Circadian rhythm is orchestrated by cellular oscillators that are present in most of the nucleated cells in the body that regulate in a time-specific manner and thus control sleep and wake time. If these cells are misaligned as in the case of circadian misalignments, it will result in the incoherent time organization of bodily processes. 

A study conducted in Japan by authors Kubo, Takahashi, Takeyama, Matsumuto, Ebara, Murata, Tachi and Itani showed the relationship between timing and length of night shift-related napping and sleep inertia. Napping is one strategy that may assist night shift workers striving to cope with sleepiness and fatigue (p. 1032). However, a major disadvantage of napping is that during the awakening process, sleep inertia is generated. Sleep inertia is described as grogginess, the transitional state of lowered arousal occurring after awakening from sleep. This process is said to impair performance. Sleepiness and fatigue are critical issues for the occupational safety of night shift workers (p. 1032). The study showed that night-shift workers are at higher risk of developing work-related diseases as compared to day-shift workers. The study provided countermeasures on how to overcome sleepiness and fatigue by means of napping, caffeine, bright light, and exercise. These countermeasures will help lessen the burden for these populations.

A second series of studies performed by Smith, Cullnan and Eastman at Biological Rhythm Research Laboratory in Chicago on shaping the light/dark pattern for circadian adaptation to night shift work, showed in laboratory studies that exposure to bright light and darkness is an effective method at reducing or eliminating the circadian misalignments produced by an abrupt shift of sleep schedule (2008). However, the study showed that while effectively scheduled bright light and darkness exposure may promote alignment of the circadian pattern to a nocturnal schedule, it also showed that very few workers maintained completely shifted schedules on their days off. The authors thus proposed a compromise in which the sleep schedule for a night worker on days off is later than for typical day workers, but earlier than sleep that occurs after a night shift.  “We propose using scheduled bright light and darkness to partially delay the circadian clock to reduce misalignment between night work and daytime sleep, but not delay the clock so far as to preclude late nighttime sleep on days off” (p. 449).

The study revealed that night shift work induces constant sleepiness and fatigue and leads to an increased incidence of cardiovascular dysfunction, gastrointestinal disturbance, cancer, productive dysfunction and is generally detrimental to physiological well-being. These symptoms or diseases are well documented in other similar studies. In addition to these symptoms, social, family and marital relationships can be disrupted due to night shift schedules (Smith, Cullnan, Eastman 2008). These social and family issues are important things to consider if the individual working the night shift has to provide a balance between work and family life.

ChronoPhysiology and Therapy published a report in 2012 regarding Circadian Rhythm sleep disorders in which Koola, Auger and Morgenthaler showed that misalignment between endogenous circadian rhythms can result in pathological disturbances in sleep patterns, erratic sleep timing, complete disassociation between the light/dark cycle, delayed sleep timing or advanced sleep timing. “Whereas these four conditions are thought to involve predominantly intrinsic mechanisms, circadian dysrhythmias can also be induced by exogenous challenges, such as those imposed by extreme work schedules or rapid transmeridian travel, which overwhelm the ability of the master clock to entrain with commensurate rapidity, and in turn impair approximation to a desired sleep schedule, as evidenced by the shift work and jet lag sleep disorders” (p. 19).  The authors further observe that “jet lag presents with both nocturnal sleep disturbances and impaired daytime alertness, in addition to other symptoms such as general malaise and gastrointestinal distress” (p.20).

Dangers to the Physiological Health of Night Shift Workers

A properly functioning Circadian Rhythm is vital to the overall health of the human body. The diminished functioning of the Circadian Rhythm increases the risks of the individual for cardiovascular disorders and heart disease. The potential suppression of the immune system also becomes more probable with disruptions in the Circadian Rhythm. A damaged immune system exposes the individual to a wide assortment of potential health risks.  Hormonal imbalance and digestive disorders can also accompany a damaged Circadian Rhythm. 

The risk of cardiovascular disorders is escalated by persistent night shift work over a long period of time. The potential for the development of heart disease increases between thirty-five to forty-five percent for a long term night shift worker. The rate of risk for stroke increases for those who have worked night shifts for a period of ten to twenty years or longer. Related physiological risks include the higher probability of high cholesterol, high blood pressure, excessive weight gain, and high blood sugar. It has been estimated that these ailments are as much as three to four times greater in night shift workers (Eastman, Lee, Smith, 2006). 

It is not entirely clear why increased weight gain is particularly problematical for night shift workers. Hormonal imbalance may play a role. Night shift workers are more likely to consume “junk” foods for the sake of convenience and take meals at inconsistent intervals. Irregular eating habits may result in an overall increase in the amount of food intake. Night shift workers are also less inclined to exercise regularly (for example, by jogging or visiting a gym) due to time and schedule constraints. 

As mentioned, gastrointestinal disorders are more likely to plague the night shift worker. These disorders can range from the comparatively mild (such as diarrhea or constipation) to the more serious (such as ulcers or intestinal infections). There is also a greater probability that a night shift worker will develop colorectal cancer. Indeed, consistent night shift work can significantly increase the risk of a variety of cancers. Night shift workers have also been found to be at higher risk for both prostate cancer in men and breast cancer in women and the longer one works on night shifts the more the risk factor for cancer increases.

A greater threat of diabetes also exists for night shift workers. The study conducted in Japan referred to above also found that the risk for diabetes increases by more than one half for those who work night or rotating shifts. The study also found that the greater the amount of time a worker spends on the job per day, the more likely it is that the worker will develop diabetes.

Persistent night shift work can also be problematical for the reproductive health of the individual. Women who work night shifts are more likely to suffer from infertility. Miscarriage is more common among night shift workers. Pregnancy complications are also more frequent including low birth weights or premature birth, and a greater risk of complications during the childbirth process. Women night shift workers are also at greater risk for disruption of the menstrual cycle and other menstrual disorders. 

It has been mentioned that the psychological health of night shift workers is also more likely to be impaired and that such disorders as clinical depression are more common among those who work night shifts. This observation may be explained in part by the possible depletion of serotonin among night shift workers. The rapidity with which serious health issues are likely to develop among night shift workers is rather varied. Routine sleeping disorders, high blood pressure, and diabetic symptoms can develop rather rapidly. Other areas of concern, such as increased risks of heart disease or strokes, seem to require a longer period of time for the accumulation of substantial risks. Studies in this area are inconclusive (McCubbin, Moore, Pilcher, 2010).

Prevention

The potential dangers to the health of night shift workers are varied and extensive. Clearly, the preservation and maintenance of one’s health should be an area of primary concern for those who work night shifts consistently or over long periods of time. A night shift worker should necessarily increase their personal attentiveness to health issues. A healthy and consistent diet is vitally important to the health maintenance efforts of night shift workers. This would include eating meals at regular intervals and consistently striving for dietary balance. A night shift worker should be particularly conscientious regarding the avoidance of excessive weight gain. 

A night shift worker should also strive to maintain a regular exercise regimen to the degree that such efforts are permitted by the worker’s schedule and time considerations. The night shift worker should avoid developing a sedentary lifestyle and should seek to remain physically active to the greatest degree possible even if, for example, such an effort were to mean lifting weights or playing tennis at odd hours.  Sleep deprivation is particularly problematical for the night shift worker and difficult to avoid. To the greatest degree possible, the worker should attempt to sleep at regular intervals. For instance, someone who works from 12 p.m. to 8 a.m. might strive to sleep from 10 a.m. to 6 p.m. each day. If such a level of regularity is impossible, then the night shift worker should try to avoid segmenting their sleeping habits (i.e. sleeping only a few hours at a time at sporadic intervals) as much as they are reasonably able.

A worker who is required by professional or financial necessity to persistently work night shifts should also attempt to minimize the impact on their health by maintaining as much consistency in their life as possible. Preferably, a night shift worker should attempt to work shifts with regular stopping and starting times as opposing to “swing” shifts where their schedule can vary widely from week to week or even from day to day. If such an arrangement is not an option with the worker’s employer, then the worker should still strive for consistency in other areas such as diet, meal schedules, number of hours of sleep obtained per twenty-four hour period, exercise regimens, and so forth. It is also of increased importance that night shift workers consult with their primary healthcare provider on a regular basis. Their general practice physician will be able to monitor those areas in which the worker’s health is most deficient (for example, potential concerns about high blood pressure or an escalated risk of developing diabetes). 

Workers who are consistently suffering from sleep deprivation are also more likely to experience a reduction in their efficiency when performing professional or occupational duties. This can not only impact the efficiency and productivity of the corporation, business, or agency with which the worker is employed but can also increase the risk of on-the-job accidents and safety hazards. A night-shift worker who suffers from depression may also experience diminished morale during the course of their job performance. Many business corporations, public sector agencies, or professional organizations now have counseling services available to employees who are experiencing difficulties. An employee whose physical or mental health is at risk because of their night shift work schedule should seek out whatever assistance may be available to them through their employer for the sake of discovering how they can better manage the stresses and difficulties they encounter (Griep, Fischer, Rotenberg, Silva-Costa, 2011).

A Personal Note

In my own professional life, I have worked the night shift for five years in the emergency department in New York City and experienced some of these symptoms that were mentioned in the studies. The most noticeable ones are the lack of sleep, inability to sleep during nights or days off, eating disorders- eating on an untimely manner, constant fatigue, feeling cold with jet-lag symptoms and gaining a few pounds. I have managed to cope by taking a nap during my regular break if only for a few minutes, dimming the bedroom light when I sleep during daylight hours and turning off all electronic devices such as cell phones and televisions. I attempt to get at least five hours of sleep before going back to work. Of course, the goal of sleeping for five hours is sometimes unrealistic due to a very busy schedule that is divided between time spent at work and at school. As for my social and family life, I manage to see my loved ones on my days off and for an added bonus, my wife also works the night shift so we get to sleep and wake up at the same time.

References

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McCubbin, J. A., Pilcher, J. J., & Moore, D. (2010). Blood pressure increases during a simulated night shift in persons at risk for hypertension. International Journal Of Behavioral Medicine, 17(4), 314-320