The Night Shift
Few nurses seem to really love working the night shift. Sure, we all know nurses who thrive on the night shift or who choose it for personal reasons. Some prefer to work when the ambience is quieter, there are no visitors, rules are less strictly enforced, and interruptions are fewer. Some work nights for family reasons -- perhaps they have young children at home and working the night shift allows them to share caretaking responsibilities with husbands/partners who work conventional daytime hours. For some, the night-shift differential is incentive enough to choose nights. However, many nurses work nights not out of choice but because they are required to do so. Usually, these nurses are farther down on the seniority list, and most will gravitate to the day shift as soon as they get the chance.
Of course, nurses are not the only night workers. It is estimated that 15%-20% of workers in industrialized countries work nontraditional hours. Intolerance to working nights even has its own label -- shift work disorder. People who have this often undiagnosed and undertreated problem have trouble getting to sleep and waking up and often experience excessive sleepiness during their shifts. Chronic fatigue in these individuals can impair productivity, safety, health, and quality of life.[1]
A Hazard to Your Health?
The health of the night-working population has not been ignored in epidemiologic research. Numerous studies have investigated the possible health consequences of working the night shift. Judging by the number of studies alone, it seems that these health consequences are significant and could represent a huge public health problem in our increasingly 24-hour society. Some of the health problems found to be associated with working nights include the following:
- Increased risk for breast cancer[2,3] and colorectal cancer[4];
- Increase in inflammatory markers (IL-6, C-reactive protein, white blood cells, neutrophils, lymphocytes, and platelets)[5];
- Irregular menstrual cycles[6]and reduced fertility[7];
- Increased risk for ischemic stroke[8];
- Increased wrist and hip fractures[9];
- Pronounced insulin response to eating[10];
- Increased development of the metabolic syndrome[11];
- Increase in type 2 diabetes[12];
- Increased blood pressure[13];
- Increased cardiovascular disease[14]; and
- Increased risk for mental health disorders, including anxiety and depression.[15]
It's a miracle that anyone is willing to work nights. The night shift does pay a little more, but can you put a price on your health?
Of course, observational studies that have linked serious health effects with working nights do not establish causation. Furthermore, a publication bias prevalent in the health literature can mean that studies with positive findings make it into print, whereas those finding no association may not. Yet, many of the negative health outcomes associated with working nights are considered biologically plausible. This plausibility, combined with evidence for one of the most serious shiftwork-related health effects -- cancer -- although limited in humans, prompted the International Agency for Research on Cancer to declare that "shiftwork that involves circadian disruption isprobably carcinogenic in humans."[16]
A phrase that jumps out here is "circadian disruption," because this is the putative link, and possibly the critical exposure variable, in the chain of causation.[17] What constitutes circadian disruption, and is it an inevitable consequence of working nights?
Circadian Disruption
Circadian disruption -- also known as chronodisruption -- is a disturbance of the circadian organization of human physiology, endocrinology, metabolism, and behavior.[17] A master biological clock, located in the suprachiasmatic nuclei of the hypothalamus, controls circadian rhythms generated by feedback loops that involve multiple "clock genes."[18] Core body temperature, blood pressure, sleepiness/wakefulness, mental performance, alertness, and secretion of hormones (such as melatonin, cortisol, prolactin, and growth hormone) are all linked to circadian rhythms.
The major synchronizers of circadian rhythms are exposure to environmental patterns of light and dark.[19] These patterns control biological cycles that repeat roughly every 24 hours (the solar day), and we are entrained to these rhythms. They allow us to have regular oscillations between sleep and wakefulness, and fasting and eating, that are critical to health. When our rest-activity cycles match the light-dark cycles of the environment, we are said to be "in phase." If a person is exposed to inadequate or irregular amounts of light at certain times of the day, circadian rhythm can be disrupted, causing asynchrony between the circadian system and the solar day.[20] This is believed to be the root of long-term negative health outcomes, such as cancer.
If you doubt that working the night shift seriously disrupts circadian organization, consider this: Working a typical night shift schedule creates biological clock stress that is analogous to the jet lag of flying back and forth between Tokyo and San Francisco every few days.[21] It is no coincidence that airline personnel who criss-cross time zones have health consequences similar to those of night-shift workers.[21]
The basis for night shift chronodisruption is exposure to light at night, when humans are supposed to be sleeping. The pineal gland-secreted hormone melatonin is the "messenger of time" that transmits information about environmental light and darkness, obtained from ganglion cells in the retina, through the hypothalamus to all tissues of the body.[15]Melatonin is synthesized and secreted at night, acting as a signal for the length of day and night. Melatonin is also a well-known oncostatic hormone that inhibits tumor growth. Light suppresses melatonin secretion in a dose- (or intensity-) dependent manner. Night sleep normally occurs during the rising phase of melatonin secretion. If a person tries to sleep during the declining phase of melatonin secretion, sleep can be shorter with more awakenings.
A Good Day's Sleep
The other significant health risk comes from the nature of sleep itself when one works at night and sleeps during the day. Fatigue in night-shift workers is the result of a classic one-two punch: shorter duration and poorer quality of sleep. Daytime sleep is more fragmented and less restorative than nighttime sleep. Night workers are not only deprived of more restful sleep, their sleep deprivation is compounded by sleep loss that builds over successive shifts because their sleep times are shorter, often by 1-4 hours, compared with night sleepers.[22] This results in a cumulative "sleep debt" and feelings of chronic fatigue that can't easily be erased with "catch-up" sleep.[23]
More than half of night-shift nurses (56%) in a study using sleep diaries were found to be sleep-deprived.[24] Night nurses more often report low-quality sleep and are more likely to use medication to get to sleep.[25] Those who work long stretches or more than 4 shifts per week are more likely to report sleep disturbances.
To make matters worse, many night-shift workers are already sleep-deprived on their first shift. This is a consequence of the tendency to switch back to a "normal" (day) schedule on their days off, so that many nurses rise early on their first work day, go to work that night, and end up staying awake for up to 24 hours or longer.
Sleep expert Ann Rogers differentiates between "fatigue" and "sleepiness." Sleepiness is a tendency to fall asleep, whereas fatigue is an overwhelming sense of tiredness, lack of energy, and exhaustion.[26] Both affect night workers. Night-shift nurses report struggling to stay awake during their shifts, and studies show that nurses do, indeed, regularly fall asleep for brief periods during the night shift or in the car on the way home in the morning.[27,28] Fatigue, on the other hand, is associated with impaired physical and cognitive functioning[26] and contributes to the increased tendency for errors.
Sleep, Fatigue, and Safety
It bears reminding that many of the worst industrial accidents in history have taken place on the night shift.[18] Over the years, nurse researchers have put their own profession under the microscope and studied the effects of fatigue on performance in nurses. The results have been equivocal, but most point to reduced performance and increased risk for errors and accidents, influencing both patient and personal safety, on the night shift.[23,29-31]
Following are some of the effects of fatigue:
- Slowed reaction time;
- Attention lapses;
- Less attention to detail;
- Compromised problem-solving;
- Impaired psychomotor skills;
- Reduced coordination; and
- More errors of omission.
Fatigue isn't the only subjective symptom experienced by nurses working the night shift. Irritability, forgetfulness, stress, chills, nausea, and eye strain are other common complaints of night-shift nurses that could affect performance or physical and mental well-being.[32] A survey of critical care nurses found that 26% had experienced personal work injuries or near injuries, 16% had been involved in patient safety incidents, and 20% had accidents or near accidents on the drive home -- all believed to be related to fatigue.[32]
Research confirms that the ability to perform tasks declines throughout the night shift, especially during the second half of the shift. The worst performance coincides with the time when body temperature is lowest, at 0400-0600,[33] a finding supported by lower levels of perceived alertness during these hours.[34] Medication errors that occur on the night shift vs the day shift are more often reported to be a consequence of sleepiness.[31]
Even partial sleep deprivation is associated with an increased likelihood of making an error and a decreased likelihood of catching someone else's error.[28] Rotating shifts, especially more rapidly rotating schedules, are associated with increased error rates in nurses.[35] Moreover, the risk for making an error or being involved in an incident increases with of the number of successive night shifts. The risk for an incident at work is 6% higher on the second night shift, 17% higher on the third, and 36% higher on the fourth.[29]
Whether these findings are due to increasing sleep deficits on the part of night shift nurses or other factors associated with working nights is not known. Increased errors on the night shift could reasonably result from several factors, such as staff shortages, increased patient-to-nurse ratios, and reduced support and resources during off hours. Admi and colleagues[36] did not find a difference in performance or rates of error between day and night shift nurses, including nurses who were less well-adapted to working nights.
Personal safety is a significant concern for nurses who are fatigued and/or sleepy. Working the night shift has been associated with an increased risk for percutaneous needle punctures, lacerations, and consequent exposure to blood-borne pathogens.[37] Extreme drowsiness while driving or cycling home, including near-miss accidents, has been reported by nurses who work nights.[28, 38] The effects of sleep deprivation on mental alertness are similar in magnitude to those seen in people with blood alcohol concentrations over the legal limit.[18]
Substantial interindividual differences in the level of cognitive and performance impairment induced by fatigue are known to exist,[39] making it difficult to predict how much sleep an individual requires to make him or her "safe." Nor is there any consensus on the extent of impairment resulting from a given amount of sleep loss.[18]
Chronotype: Which Bird Are You?
People often describe themselves as being either a "morning person" or a "night person." Some people feel better and are more alert and energetic at different times of the day, a characteristic known as "chronotype." Putting an avian twist on chronotype, people are often characterized as "larks" or "owls."
If you prefer to rise early, feel most alert and perform best in the morning, and go to bed early, you are an early chronotype, or lark. If you prefer to sleep late, work best later in the day, and stay up well past midnight, you are a late chronotype, or owl. Those who are somewhere in between (which is most of the population) are hummingbirds. Experts say about 1 in 10 people are larks, 2 in 10 are owls, and the rest are hummingbirds.
Of course, these labels are slightly misleading. Even "owls" don't stay up all night like some species of owls. It is simply not natural for humans to do so, and human "owls" have difficulty resetting their internal clocks if compelled to stay awake all night.
Adaption to the Night Shift
Recently, a research team at Vanderbilt University examined how chronotype, along with an individual's sleep strategies, might influence how well a nurse adapts to the night shift.[40] Gamble and colleagues hypothesized further that genetics, and in particular the body's "clock" genes, might play a role in how well a nurse adapts to working nights.
They recruited a convenience sample of 388 nurses who worked 12-hour shifts (days or nights) at a university hospital. Most (331) were women, and their average age was 36.5 years (range, 22-76 years). Participants completed self-reported surveys on sleep-wake patterns and had blood drawn for genetic analyses. "Adaptation" was a composite of variables, such as how the nurses felt, fatigue levels, regularity of sleep patterns, how long it took them to get out of bed, how much caffeine they ingested, and how likely they were to fall asleep during the day.
The researchers found that night-shift nurses reported significantly poorer adaptation to their work schedules than day-shift nurses. The former group had significantly later chronotypes than the latter. Examining the relationship between chronotype and adaptation to shift work, they found that earlier chronotypes had higher adaptation scores for the day shift and lower scores for the night shift. Later chronotypes had intermediate adaptation scores for both day and night shifts.
Although previous research has found that night-shift nurses get fewer hours of sleep than day-shift nurses,[27] sleep duration in this study did not differ between day- and night-shift nurses. However, that night shift nurses had poorer adaption to their work schedules suggests that adaption is affected not only by how much sleep a nurse gets but when he or she sleeps relative to working. This, in turn, is influenced by an individual's sleeping patterns -- the strategies an individual uses for switching back to a normal sleep schedule on days off from work and for reverting back to nights.
In the genetic analyses of the nurses, some changes in the "clock" genes were associated with alcohol and caffeine consumption and sleepiness, as well as sleep characteristics. Many of these results were specific to the type of shift, suggesting an interaction between the genes and the environment (in this case, the "environment" was shift work).
This study was unique in identifying and describing both the working and off-working sleep strategies of night shift nurses. A few nurses remain on "nights" even on their nights off -- staying up all night and sleeping during the day, a strategy favored by older and more experienced nurses. Far more common, however, was trying to switch to a "normal" sleeping schedule (eg, sleeping at night) on one's off days, a strategy followed by half of the study participants. These nurses generally tried to sleep in as late as possible on the day of their first night shift to ease the transition to nights. In contrast, a quarter of nurses deprived themselves of sleep by rising at an early hour on the day of their first night shift and forcing themselves to stay awake for 24 hours. It is perhaps no surprise that these nurses were the most poorly adapted to working nights and were more likely to report dozing off at work during sedentary activities.
How to Survive the Night Shift
The extent to which human circadian rhythms can adapt to a night shift is not known. Nor is it known whether such adaptation would negate the health consequences of working the night shift. However, the findings of such studies as that conducted by the Vanderbilt team suggest that on some level, at least some nurses can adapt to working nights.
A member of the Vanderbilt research team, Carl Hirschie Johnson, spoke with Medscape about the practical implications of the study. "With respect to adaptation, the best strategy is staying awake at night, and sleeping during the day, even on your days off, if your family obligations allow you to do that. To entrain yourself, you have to simulate a reverse day. Sleep in a very quiet, very dark room (or use a blindfold). At work, seek out brightly lit areas. You need bright light exposure, but most indoor lighting is insufficient. Don't nap during your shift. If you can't stay on this schedule (and fewer than 5% of nurses in the study did), the next best strategy is that of sleeping late before your first night shift, rather than going without sleep."
Some nurses seem to be unable to adapt to working nights, no matter how hard they try.[27]Suggestions for mitigating the effects of shift work and fatigue include the following[25]:
- If you work 8-hour rotating shifts, rotate clockwise (days, then evenings, then nights);
- Avoid rapid rotation (eg, working different shifts in the same week);
- Follow a regular sleep schedule regardless of which shift you are working;
- Use room-darkening or blackout shades in your bedroom;
- Spend as much time as possible in brightly lit rooms;
- Wear sunglasses to block blue light when driving home in the morning;
- Don't schedule appointments or activities during your routine sleeping hours;
- After your last night shift, sleep for 4 hours;
- Avoid eating large meals within 4 hours before sleeping;
- Avoid caffeine and nicotine before sleeping; and
- Seek exposure to bright light after waking.
Many other measures have been assessed for their value in helping workers adapt to shift work, including supplemental melatonin, chemical sleep aids, use of stimulants, and physical exercise.[41]With the exception of physical exercise, all of these measures have potential drawbacks. However, a regular exercise program can benefit night-shift workers not only by helping them tolerate the night shift but also in reducing the somatic symptoms associated with poor sleep and working nights.[41]
My Kingdom for a Nap
Naps are often recommended, and frequently practiced, as an effective strategy for staving off sleepiness on the night shift.[42] On the surface, napping makes sense. Many people nap, if they are lucky to have this rare privilege, to counter sleepiness at other times of the day. The National Sleep Foundation recommends "short naps breaks throughout the shift" for night workers, maintaining that napping can be essential for some shift workers.[43] Short, restorative naps at night are widely believed to help reduce sleepiness and fatigue and increase alertness. In a small study, 10 of 13 critical care nurses who napped regularly during breaks reported improved energy levels, mood, vigilance, and decision-making abilities.[44]
In a larger, Internet-based survey,[32] to which 536 critical care nurses in Canada responded, nurses were asked about their typical napping practices during the night shift napping practices. In this sample, 66% reported napping during their breaks, and 30% of those nurses believed that their care was safer after a nap. Most (80%) believed that napping was beneficial. Even though the primary reason for a nap might be sleepiness, nurses who are struggling to stay awake may also fear that without a brief nap they are unsafe to deliver patient care.
More objective research, in both the laboratory and work settings, has yielded moderate support for the benefits of night shift-napping in terms of performance and self-reported measures of fatigue and sleepiness,[45-49] even when the nap is short and the sleep is of poor quality.[50] These findings have been fairly consistent despite varying nap durations. Sleeping on the job during the night shift may also partially compensate for the shorter daytime sleep at home among night workers.[51]
Why Not Nap?
Many of the studies conducted to date identified a potential disadvantage of napping -- a phenomenon known as "sleep inertia." Sleep inertia is a period of disorientation and performance decrement that can occur immediately upon waking from a nap.[52] If you have ever taken a nap in the middle of a night shift, you are familiar with this unpleasant, groggy feeling. Although sleep inertia is transient, some research suggests that the problem correlates with the length of the nap[53] and recommends short naps, of 15-20 minutes. A meta-analysis of studies of napping as a countermeasure for fatigue concluded that sleep inertia, if present, was not a significant concern because it was counteracted by the beneficial effects of the nap.[52]
Despite widespread desire for the option of napping on the part of night-shift nurses, a few considerations argue against this practice. Carl Johnson explains why napping during the shift might be a bad idea for some workers. "In contrast to the usual situation of taking a mid-day nap when you are on a more typical daily schedule, taking a nap when your body is telling you it is "sleeptime" is likely to not only prolong the nap into a full-blown sleep episode (which will lessen alertness on the job after the "nap" is over) but also to make the phase-shift to a night-active phase even slower." In other words, if you are trying to truly adapt to night work and day sleeping, taking a nap at night is counterproductive.
I'm Not Sleeping on the Job, I'm Napping on My Break!
The benefits of napping have not led to universal adoption of this practice during the night shift by nurses or encouragement of this practice by employers. Barriers to napping include lack of designated nap facilities, patient care demands, understaffing, interruptions, and perceived lack of management support.[54] Nurses are made to feel guilty for napping at night, and in some hospitals they are disciplined for doing so, even when the nap is taken during scheduled breaks.[54]
This guilt is not entirely unfounded. Most employers do not currently allow napping in the workplace, but this could soon change. The National Sleep Foundation maintains that napping can reduce fatigue-related accidents and workers' compensation costs, making a ban on napping a legal liability.[43] Efforts to make workplace policies nap-friendly will be increasingly important.
According to nurses, in addition to administrative support for napping, the following provisions would improve their ability to take a restful nap during the night shift[32,54]:
- A quiet, safe, clean "nap room" that is close to the unit and has a private area for each user (eg, not a multiuse room or staff lounge used for other purposes);
- Comfortable napping surfaces, such as beds, sofas, stretchers, or reclining chairs;
- Blankets and pillows, or storage areas for staff to bring their own items;
- Low lighting levels, preferably with dimmer switches;
- Timers with audible alarms to awaken nappers at the end of the nap (20 minutes is ideal); and
- Relief from patient responsibilities during nap breaks.
Still, whether napping should be a stop-gap measure to combat unanticipated sleepiness or part of a planned sleep-wake strategy to promote sleep health in regular night-shift nurses is not currently known. Nor is there much known about the effects of napping at night on subsequent sleep quality, or whether napping regimens can counteract the negative physiologic sequelae of working nights in the first place.
A Professional Imperative: 24-Hour Care
Nursing is, and always will be, a 24-hour business. We must find the healthiest and safest ways for nurses to work at night, or we might as well close the hospital doors.
The idea that some people might be genetically better suited to working nights is intriguing and supported by evidence suggesting that nurses who choose to work the night shift find it less disruptive.[55] Perhaps future research will better identify why certain individuals adapt more easily to nights and clarify the best methods for individual adaptation to shift work. Whether better adaption will overcome the negative health outcomes associated with working nights remains to be seen.
The Danish government recently awarded compensation to a number of women who developed breast cancer after years of working nights,[56] a signal that the public health problems associated with working nights are being taken seriously. In addition, the problem of fatigue in healthcare workers is receiving attention from many quarters, including the Joint Commission, which recently issued a sentinel event alert on this topic.[57] Although the focus of the alert is on fatigue caused by extended work hours, the recommendations offered have equal applicability to fatigue caused by night-shift-related sleep deprivation.
In the meantime, love it or hate it, if you have a tip for surviving the night shift, please share it in the comments below. I will compile your tips and publish a follow-up article here on www.uselessdesires.co.uk
References
- Thorpy M. Understanding and diagnosing shift work disorder. Postgrad Med. 2011;123:96-105. Abstract
- Schernhammer ES, Laden F, Speizer FE, et al. Rotating night shifts and risk of breast cancer in women participating in the nurses' health study. J Natl Cancer Inst. 2001;93:1563-1568. Abstract
- Hansen J, Stevens RG. Case-control study of shift-work and breast cancer risk in Danish nurses: impact of shift systems. Eur J Cancer 2011 Aug 16 [Epub ahead of print].
- Schernhammer ES, Laden F, Speizer FE, et al. Night-shift work and risk of colorectal cancer in the nurses' health study. J Natl Cancer Inst. 2003;95
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