What makes me tick…tock? June 2012Lesson 6: What happens to humans when normal rhythms are disrupted?

Sleep or work? Circadian influences on hospital shift work

Many professions require working long hours during the periods of the day when most people sleep. It may be hard to imagine, but many people end their work shift as many of us are just beginning our day. Health professionals such as nurses often work irregularly long shifts throughout a given week. A nurse could potentially work a shift during regular daytime hours, and then in the same week work a night shift until the next morning. While the need for constant patient care is often unavoidable, variable work shifts such as the kind nurses often work can cause significant circadian disruptions.

One study examined the impact of work shifts on the sleep schedule, sleepiness, and accident rate of nurses. Work shifts were generally classified as day/evening, night, or a variation of the two. Day or evening shifts start during regular daytime hours such as 7:00 AM – 7:00 PM or 11:00 AM – 11:00 PM Night shifts begin during the night and end the next morning, such as 11:00 PM – 11:00 AM

Nurses often have to quickly adjust their daily lives to varying work schedules. For example, what would the typical sleep schedule of a nurse working a day shift on Monday and then returning to work an evening shift on Tuesday look like? The nurse would need enough sleep before each shift to properly prepare for the potentially intensive work routine of patient care. The nurse may sleep Sunday night at 10:00 PM, wake up at 6:00 AM on Monday, and begin his or her shift sometime at 7:00. The Tuesday evening shift at 11:00 PM would begin during his or her regular period of sleep. A nurse may start sleeping at 1:00 PM Tuesday afternoon to get enough sleep to prepare for the night shift.

This may be a more challenging task then it appears. External cues such as sunlight cue many of the natural endogenous rhythms of our bodies. These circadian rhythms strongly influence the onset and duration of sleep. Humans are diurnal and typically sleep during the night when the amount of sunlight is low. So while the nurse in the previous example needs to sleep during the day to prepare for the night shift, this time period would strongly oppose his or her optimal sleep schedule and would conflict with his or her endogenous circadian rhythms. Of course in reality, nurses must develop a routine which allows them to prepare for their irregular work schedules. Often times, this does in fact require them to sleep during unusual periods of the day, forcing them to overcome their body’s natural opposition to daytime sleep. Interestingly, the study found that the sleep schedule varied between

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What makes me tick…tock? June 2012Lesson 6: What happens to humans when normal rhythms are disrupted?

work days and days off (Figure 1). Most nurses reported sleeping between 5–7 hours the night before a work day and more than 7 hours the night before a day off. Likely, the nurses slept more on their days off to recover from the strenuous work shift hours.

Sleeping is one of many natural processes influenced by circadian rhythms. Nurses can disrupt this natural cycle in several ways. First, nurses may sleep during the day to prepare for a night shift. While routine may help normalize the effects, sleeping during the day opposes the body’s natural sleep pattern and can potentially have side effects other than fatigue. Second, nurses may also sleep irregular schedules during a given week. Even if a nurse does typically sleep during the day due to work, a nurse may sleep during the day to prepare for a Monday nightshift and then return to a more normal sleep schedule on their day off to prepare for a Wednesday day shift. The irregularity of these schedules may be necessary to prepare for a long work shift, but it can also disrupt the body’s natural rhythms. Third, the study found that the surveyed nurses tended to sleep more on their days off than on workdays. This may seem negligible, but it’s important to remember that many of the body’s processes function in rythmic patterns. So while staying up through the night to complete an assignment may seem to be erased by more sleep the following night, sleep disruptions aren’t fixed easily as if they were a bike chain which slipped from its gear. Stretching it out will not simply spring it back into place because these are naturally recurring rhythms; and disruptions can cause many of these rhythms to fall out of sync with one another. All of these factors can potentially cause circadian disruptions, which could potentially have health consequences for shift workers such as nurses and impact their work performance. The study found that nurses with rotating work shifts were 2.5 times as likely to report an accident or error when compared to typical day/evening shift nurses. Rotating and night nurses were also more likely to nod off while driving compared to day shift nurses. The effects of irregular sleep schedules can have potentially serious consequences on daily life.

Obviously the demands of daily life occasionally require many of us to maintain an irregular sleep pattern. And while stressful, its likely many of us do recover from the occasional all-nighter. But the career of a nurse requires several routine all nighters throughout the week. The demands of a particular hospital could potentially change from day to day. And medical professionals such as nurses not only must adjust to these irregular work shifts, but also must be prepared to address the constant concerns of patient care. These nurses subject themselves to irregular sleep schedules which could potentially cause circadian disruptions. Additionally considering that the study reported the use of medication and/or alcohol by many of the nurses to aid in sleeping, shift work can subject nurses to complications from circadian disruptions, medication side effects, or frequent alcohol use. The interactions between these complications could potentially create long term health consequences for the nurses. Hospital administration which applies circadian principles to hospital shift-work policies could limit the amount of alternating work schedules and potentially improve the health of medical professions such as nurses and the safety of the patients.

Figure and information fromGold DR., Rogacz S., Bock N., Tosteson TD., Baum TM., Speizer FE., Czeisler CA. (1992) Rotating shift work, sleep, and accidents related to sleepiness in hospital nurses. American Journal of Public Health 82: 1011–1014.

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