Table 1.

24 hours in the life of Dr. S.W. on night shift.

1 PM	When Dr. S.W. went to bed after her second night shift it took a while until she fell asleep. Her thermoregulation is out of phase, and she consumed several cups of coffee. Both aspects likely interfere with sleep initiation, maintenance and deep sleep (34). Normally, she would have lunch now, her stress systems would be active, and the bright light of the midday sun would suppress her melatonin levels (35). In bed however, the light that breaks through the window sealings and the noise from outside fragment and shallow her sleep.
5 PM	Dr. S.W. woke up but does not feel well rested or refreshed. Presumably, she lacked slow wave sleep (SWS), the deepest form of sleep that normally helps to flush away metabolites from the brain parenchyma (36) and to clear sleep regulatory substances like adenosine, tumor necrosis factor (TNF) and interleukin-1 (IL-1) that induce fatigue and sleepiness (37). When she looks into the mirror, she notices that her skin is pale and that she has an unhealthy appearance. These are findings that also emerge after experimental sleep deprivation (38). Sleep supports anti-oxidative and regenerative processes and a lack thereof impairs skin integrity (39). Moreover, sleep loss is associated with systemic chronic inflammation (SCI) that is a likely mechanism of fatigue, sleepiness, bad mood, cognitive impairments and other feelings and symptoms of sickness (40). It is getting dark already and Dr. S.W.’s breakfast consists of three cups of coffee and, as she failed to buy groceries, a chocolate bar. She comforts herself that caffeine not only antagonizes the sleep-inducing substance adenosine (41) but may also counteract SCI that evolved due to sleep loss (42). Maybe she should take some vitamin D as well to fight against the inflammatory processes (43).
9 PM	Dr. S.W. heads to the clinic for her third night shift and takes the car instead of her bicycle. In the doctor’s room she switches on all the lights and drinks a cup of coffee to become alert (34). Normally, her melatonin would rise, and her stress systems would calm down at this time of the day (35). These changes would induce an increase in skin temperature, a decrease in core body temperature and in this way her body would get prepared for the sleep period (34, 44, 45).
1 AM	In the patient rooms and the ward corridor the light is dimmed, and the volume of the alarm sounds were turned down. The intensive care unit (ICU) staff generally agrees that the patients should sleep at night to recover (46). On a regular wake-sleep cycle also Dr. S.W. would be in deep SWS now. Her immune system would be boosted by increases in growth hormone, prolactin and aldosterone and very low cortisol and catecholamine levels (35, 47, 48). These hormonal changes presumably also support anabolic processes like cell proliferation and cell growth, as well as anti-oxidative and regenerative processes (49, 50). However, Dr. S.W.’s hormone secretion is disturbed.
5 AM	Dr. S.W. is freezing. Normally, her core body temperature would be at minimum now and her internal clock would increase the propensity of rapid eye movement (REM) sleep. Neurotransmitters of the sympathetic nervous system (SNS) such as the catecholamines epinephrine and norepinephrine now would reach nadir levels (51). For the staff of the ICU this night, the opposite holds true. Dr. S.W. hears a red alarm. A patient has a cardiac arrest, and she starts resuscitation. After stabilizing the patient, the ICU team sits together, they drink coffee and eat potato chips. They agree that night shifts favor unhealthy diets (18, 52), substance abuse (23), social isolation (20) and TV time and that these adverse lifestyle habits may increase mortality (53).
9 AM	Dr. S.W.’s internal clock activated her stress systems, leading to reduced feelings of fatigue and sleepiness. She drives back home and reflects her life. She loves being at the ICU. It is a meaningful work and there is no doubt about the necessity of 24/7 shifts in contrast, to e.g., night shifts in the supermarket. However, increasing economic pressure in health care leads to displacements of routine procedures into the evening and night hours with adverse consequences for health care workers, their performance and their stress levels and for patient outcomes (54, 55). When she gets out of the car, she wonders whether seeking a specialization in dermatology or rheumatology would be a healthier career option.