Stress Exhibited in Night Shift Workers and Possible Interventions

By Mark Starmach  (19/4/2009)

Physiological, Psychological and Social Effects of Stress on
Night Shift Workers and Possible Interventions

In the 24-hour society we currently inhabit, shiftwork has become an increasingly prominent fixture for businesses to accommodate for continuous output and productivity. In his examination of this new practice, Giovanni Costa notes this developing social trend, by citing a recent EU Survey on Working Conditions which found only 24% of employees undertake a standard 8 hour shift, indicating that ‘non-standard’ working hours, including night shift work, were scheduled to the majority of the workforce (G. Costa, 2003). According to the Australian Bureau of Statistics, in Nov 2006, 1.2million employees usually worked shift work. With this recent change in human resource management, studies into the possible health risks and factors of working through the night have been rigorously produced. Overwhelmingly, research found that significant increases in the probability of heart disease, digestive problems, diabetes and a greater risk in developing cancer were exhibited in night workers. Studies have indicated that these increased health risks can be attributed to the disruption of homeostatic functions such as circadian rhythms, as the body and brain cope with the stress of this imposed behavioural schedule by erratic and sustained non-typical hormonal discharges (D.Ribeiro et al, 1998), (L.C. Coffey et al, 1988).

Additionally, the stress generated in adapting to night shiftwork has adverse psychological and social effects, including decreased mental performance, alertness, quality of sleep and social participation, and an increase in dependence to nicotine and caffeine, and susceptibility to depression, as pituitary-adrenocortical dysfunctions can be correlated between undergoing night work and Chronic Fatigue Syndrome (G. Leese et al, 1996). These findings have prompted greater interest in monitoring the health and wellbeing of night shift workers and have proposed interventions of coping with circadian disturbance and a physiologically demanding workload.

Of all the sources for stress in undertaking night shift work, perhaps the most impending cause is adapting to an imposed behavioural schedule against the body’s natural circadian rhythms of hormone secretion and suppression. The stress of adapting to working nocturnally, coupled with the stressful nature of work itself, is highly depreciative to the mind and body, and the longer the person takes up this form of work, the more stressed they become, as coping mechanisms are rapidly compromised.

Typically, night shift work facilitates for rapid-paced work with a heavy workload in a stressful environment, such as emergency services, hospitals, mining, factories, manufacturing and hospitality. The environment requires consistent attention and intervention, for example a nurse needs to prioritise patients and a convenience store clerk is constantly alert for hold-ups. Consequently, workers exert themselves over a prolonged period of time and suffer from a lack of breaks. As the stressful work environment triggers the ‘flight-or-fight’ response, this in turn places an extraneous conflicting load onto the hypothalamus, as it must manage both circadian functions whilst ensuring the body remains energised. As a direct result of depriving the body of sleep and instead exposing it to such demanding labour, the worker begins to show symptoms of short-term physical and long-term mental stress. The response to this stress elicits undesirable coping mechanisms, such as irregular hormonal and metabolic responses, which have a number of negative physiological, psychological and social implications.

Due to this prolonged confusion between the priority to sleep and to work, the endocrine system begins to secrete hormones into the blood stream to cope with the stressful environment. The pineal gland begins to release melatonin at roughly 9pm to induce drowsiness and sleep, in order to sustain the homeostasis of the circadian rhythms and the light/dark cycle. These rhythms dictate the approximate 24-hour biological cycle by which our chemical, psychological and behavioural functions operate, and can be endogenously regulated by the presence and absence of daylight. It is important to note that even though this cycle is disrupted, it is not altered by nonphotic activities at night such as exercise or exertion (that is, it does not shift backward or forward permanently) because it is strictly light-mediated to enable for behavioural flexibility without compromising circadian phases (SW. Cain et al, 2007), and therefore continues to function irrespective of the person’s activity. When undertaking night shift work over a long period of time (greater than 2 years), this prolonged disruption of the circadian rhythms can be linked to sleep disorders, migraines, CFS, SAD, depression and recently, breast cancer (R G Stevens, 2005).

As the worker is operating against their circadian rhythms, the adrenal glands need to counteract the heightened melatonin levels by discharging more adrenaline than usual, aiming to increase blood flow to the heart and keep up energy levels. Additionally, the adrenal cortex needs to release more cortisol in order to convert proteins and fats into glucose, which serves to keep the body active and fuelled. The problem with these hormonal reactions is that they aim to deal with short-term stress, however as night shift work is often intense and uninterrupted, these increased hormone levels are sustained over long periods of time, which depletes the body’s coping resources and can begin to degenerate and harm the body itself. The effect of adrenaline in constricting blood vessels, together with the effects of cortisol can cause blocked arteries, clots, deep vein thrombosis, heart disease and digestive problems (such as diabetes), which supports research and traits in night shift workers.

As well as irregular hormonal responses to stress, metabolic anomalies have also been observed in night shift workers. In his 1998 journal article, Ribeiro et al expanded on previous studies of altered postprandial hormonal and metabolic responses to meals taken during a simulated shift work environment. Of what this experiment found, the most insightful discovery was the shifting of mean melatonin peak levels from approximately 0350hr at baseline levels to the greatest shift of 1950hr after 6 days, before reaching a midway point after 8 days at 2330hrs (D. Ribeiro et al, 1998, p307.), suggesting a temporal shift in melatonin production. Also of interest are the significantly higher levels of TAG (from the thyroid gland) after the shift, which are hypothesised to operate on a diurnal system, suggesting that these concentrations have shifted and accumulate during the day, as insulin levels are lowest at night. Heightened TAG levels may explain a higher incidence in coronary heart disease in night shift workers (D. Ribeiro et al, 1998, p310). These irregular metabolic responses to meals in shift workers can be derived from placing an immense amount of conflict and stress unto the body’s circadian rhythms and coping mechanisms. 

Of interest, is that over time, these physiological and hormonal responses to stressors can begin to infiltrate and degenerate the worker’s psychological well-being. The mental stress placed on employees to maintain optimal productivity whilst depriving their body of sleep can result in reduced mental performance, an inability to relax and a lowered level of self-esteem. Because the body is working against its inbuilt light/dark cycle, the brain limits its neurocognitive ability as it aims to reduce thought and induce sleep. Capacity levels of the working memory, which typically hold only 5-9 chunks of meaningful information, average more toward the lower capacity when in the sleep-inducing phase of the circadian cycle. The brain can be said to ‘shunt’ its higher cognitive process during this period. This trait of conscious cognitive deficit can also be seen in sufferers of ‘jet lag’ (K. Cho et al, 2000). This results in significant mental strain placed on the worker as information processing is limited, due to stress on specific neurocognitive domains such as attention and higher cognition, and mistakes often take longer to comprehend and rectify, as neural systems are highly susceptible to sleep deprivation (J.S. Durmer et al, 2005). As a result, night shift workers are more prone to accidents, workplace injury and mental “burn-outs”. 

Because of increased and prolonged adrenaline release, many workers find it very difficult to relax after their shift, and many choose to rely on smoking as a method of relaxation. Similarly, caffeine is a common addiction in forcing the body to work and to maintain the level of energy needed. These substance dependencies can have negative social and health impacts on the worker. However, perhaps the most alarming psychological stress is the links between night shift work and Chronic Fatigue Syndrome. In his 1996 article, Graham Leese et al examines the correlations between pituitary-adrenocorticol dysfunctions in CFS sufferers and night shift workers, such as high blood plasma ACTH concentrations (adrenocorticotropic hormone), low serum cortisol concentrations and reduced ACTH responses. These hypothalamic defects are shared in both sufferers of CFS and SAD, and suggest that night shift workers are vulnerable to clinical depression and other mental health problems (G. Leese et al, 1996, p1870).

Night shift workers however, do not appear as stressed as they are. Although adrenaline is running through their blood stream at alarmingly high levels, the secretion of melatonin serves to partially obscure some of the adrenaline’s effects, and subsequently workers underestimate their stress levels whilst working. On the other hand, after the shift is over, workers feel very impatient, tense, irritable and stressed. Upon interviewing three workers at a bakery (see references), who work on average 5 days a week and a shift from 2am to 10am, my questionnaire found that all three felt full of energy when they undertook work, but at the same time felt stressed and restless. This can be attributed to the increased levels of adrenaline forced into their blood stream during work, and subsequently less cortisol is needed as melatonin serves to somewhat counteract adrenaline’s effects.

However, all subjects noted they felt an immense come-down and groggy period after they had finished their shift. This can be tied to the partial shifting of the body clock and the subsequent hormonal discharges to keep the body operating which have a negative downside once work is finished. On a social level, subjects indicated a generally lower level of happiness, with one worker (working at night for 7 years) indicated never feeling happy.

Fortunately, there are a number of interventions night shift workers can undertake to reduce the stress of depriving their body of sleep, and instead lead happy and healthy lives. A lot of these methods aim to increase the body’s ability to cope when it is deprived of sleep, and are centralized mainly around diet, nutrition and exercise. Paramount to all these interventions is the concept of consistency, as this promotes a steady and predictable homeostatic system and lifestyle for the body to maintain. The body needs time to rest, to restore and repair damage done to it during activity, however the problem with night shift work is that getting enough restful sleep can be a challenge. Of the workers interviewed, most indicated that they had trouble falling and staying asleep. When so much of our activity and energy levels is dictated by the amount of rest we get, it is imperative especially for night shift workers to maintain a consistent sleep pattern. By enforcing a shifted sleep pattern (eg. from 6pm-2am), when melatonin secretion only occurs naturally at approximately 9pm, this can be the difference between restful and restless sleep. Eating hearty and healthy meals has been proven to initiate melatonin secretion, and other nutrients such as carbohydrates and bases (such as milk) have a slowing and drowsy effect on metabolism and brain activity, thus allowing the worker to fall asleep easier. With proper rest, the body is more able to adapt to the imposed behavioural structure of night shift work.

Dually, a proper diet is necessary to improve and strengthen the body’s natural coping mechanisms. Avoiding processed foods, saturated fats, sodium and instead eating foods high in protein and iron is very beneficial in minimising the effects of working against circadian rhythms, and also decreasing the health risks aligned with night shift work. The risk of developing diabetes and coronary heart disease can be reduced by a high-carbohydrate pre-meal, which eliminates the effect of the diurnal rhythm of glucose tolerance (Ribeiro et al 1998), as this and lipid tolerance can be influenced by the nutrient composition of the previous meal (Service et al 1983). This can improve over all digestion and metabolism, and is also recommended by nutritionists. Keeping well hydrated before, during and after the shift is also crucial to replenish the body and avoid exhaustion.

Another key intervention to counteract the adverse effects of working at night is undertaking exercise. As the body comes down from the high adrenaline levels of working, it is important to use up excess adrenaline to avoid concentrations and tightened blood vessels, but also to allow the body to relax. After a night shift, the worker can counteract increased hormonal activity by exercising or working out before having a big meal as lunch. During the shift, it can also be beneficial to give the worker sufficient breaks. All of the workers interviewed agreed that they were not granted sufficient breaks, and often times, the nature of the work does not allow for a temporary stop in production. Instead, workers unable to take sufficient breaks can undergo short stress relief exercises, such as closing their eyes, breathing deeply whilst contracting and relaxing their muscles for 1 minute, before resuming work again. However, all the health-related impacts of night shift work accentuate the need for regular physical and mental health check-ups given to employees (G. Costa, 2003, p87).

The risk too of psychological deficit also suggests undertaking mental exercises to train the brain. If the worker does become mentally overwhelmed, it is important to resist the temptation of smoking to relieve stress or relying on caffeine to improve alertness (as is a trait in night shift workers), and instead undertake activities during the day which improve memory and general mental ability. It is also suggested that avoiding day-time naps, especially in sun-lit rooms allows the circadian rhythms to cope more naturally with the shift (M Simeonova, 2003). As night shift workers are at risk of developing depression, CFS and SAD, it is also recommended that workers maintain an optimistic state of mind. This can be achieved through releasing endorphins into the blood stream, either through exercise (such as jogging), undertaking an enjoyable hobby, joining a social club, laughing and practicing positive thinking. Instead of dreading the alarm clock at 2am, it’s best for workers to adopt a less negative attitude. It is important that night shift workers do not detach themselves from social relationships and commitments, but instead maintain these with respect of their body’s need to sleep and recover.

As discussed, physiological, psychological and social stress exhibited in night shift workers derives predominantly from the disruption of the body’s circadian rhythms, sleep deprivation and instead undertaking physical work, and in adapting to this as a routine, the stress begins to scar and degenerate the worker’s mind and body itself. However, with consistent homeostatic maintenance and monitoring, by eating correctly, keeping a proper sleeping pattern, exercising and substituting behaviours, the stress associated with night shift work is drastically blunted and the body is armed with strong and efficient coping mechanisms.

1. G. Costa, “Shift Work and Occupational Medicine: An Overview”, 2003, Oxford Journal of Occupational Medicine, volume 53, issue 2, pp. 83-88

2. Australian Bureau of Statistics, catalogue #6342.0, “Working Time and Arrangements”, November 2006

3. LC. Coffey, JK. Skipper, FD. Jung, “Nurses and shift work: effects on job performance and job-related stress”, Journal of Advanced Nursing, 1988

4. DCO. Ribeiro, SM. Hampton, L. Morgan, S. Deacon, J. Arendt, “Altered Postprandial Hormone and Metabolic Responses in a Simulated Shift Work Environment”, 1998, Journal of Endocrinology,
volume 158, issue 3, pp. 305-310

5. G. Leese, P. Chattington, W. Fraser, J. Vora, R. Edwards, G. Williams, “Short-Term Night-Shift Working Mimics the Pituitary-Adrenocorticol Dysfunction in Chronic Fatigue Syndrome”, 1996, Journal of Endocrinology, volume 81, issue 5, pp. 1867-1870

6. SW. Cean, DW. Rimmer, JF. Duffy, CA. Cziesler, “Exercise Distributed across Day and Night Does Not Alter Circadian Period in Humans”, 2007, Journal of Biological Rhythms, volume 22, issue 6, pp. 534-541

7. RG. Stevens, “Circadian Disruption and Breast Cancer: From Melatonin and Clock Genes”, 2005, Epidemiology, volume 16, issue 2, pp. 254-258

8. K. Cho, A. Ennaceur, JC. Cole, CK. Suh, “Chronic Jet Lag Produces Cognitive Deficits”, 2000, Journal of Neuroscience, volume 20, pp. 1-5

9. JS. Durmer, DF. Dinges, “Neurocognitive Consequences of Sleep Deprivation”, 2005, Seminars in Neurology, volume 25, issue 1, pp. 117-129

10. FJ. Service, LD. Hall, RE. Westland, PC. O’Brien, VLW. Go, MW. Haymond, RA. Rizza, “Effects of Size, Time of Day and Sequence of Meal Ingestion on Carbohydrate Tolerance in Normal Subjects”, 1983, Diabetologia, volume 25, pp. 316-321

11. M. Simeonova, “Healthy Lighting, From a Lighting Designer’s Perspective”, 2003, Milena Lighting Design

12. Prepared own questionnaire and asked 3 night shift workers employed at Baker’s Delight in Cherrybrook to fill it out accurately and honestly. Please see a copy of the questionnaire linked here.