ARTICLES

Shift work and doctors' health

Authors: John Hobson 

Publication date:  09 Oct 2004

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Thanks to new European legislation on working hours, more doctors will have to work unpopular shift systems. John Hobson spells out how shift work can affect your health and performance, and what you can do to protect yourself

Shift work is a recognised risk factor for ill health and can affect safety and social wellbeing. Although it has become a fact of modern life, shift work is certainly nothing new in medicine, which has always provided care around the clock. The implementation of European legislation is new, however, and since 1 August 2004 all doctors, including those in training, should be working within the guidelines, which stipulate a maximum 58 hour working week for doctors. The European Working Time Directive provides guidelines on breaks and continuous working and requires employers to assess the health of shift workers. The directive is causing problems throughout Europe, and most countries will be left with a shortfall of doctors if they apply the rules fully.

Traditional medical shifts

In the meantime, most doctors at some stage in their careers will experience an extended period of non-standard working hours because of their on-call duties. This is unlikely to be the classic rotational shift pattern worked by those in industry, nursing, or the emergency services. In medicine, historically, doctors have worked a normal day and then remained on call through the subsequent night or weekend. This has more far reaching effects than working a rotational shift pattern—not only is there disruption of the normal circadian rhythm, but fatigue or daytime sleepiness as a result of prolonged working periods can have significant effects on general efficiency.

Health hazards of night work

Even if doctors adopt classic rotational shift patterns, they and their employers need to be aware that these shifts can have an effect on health. [1] [2] Night work causes a mismatch between the circadian timing system and environmental synchronisers, and many psychophysiological functions, such as the sleep-wake rhythm, are disrupted.

Shift lag syndrome

In the short term, “shift lag” syndrome is characterised by feelings of fatigue, sleepiness, insomnia, disorientation, digestive trouble, irritability, poorer mental agility, and reduced performance efficiency. These are important contributory factors to human error and accidents at work, and are increasingly recognised as being common in healthcare workers compared with workers in other sectors, such as in the airline industry, where working patterns are more tightly controlled.

In the longer term shift work can lead to more severe disorders, although individual susceptibility varies considerably. Age, gender, personality traits, and behaviour such as neuroticism, rigid sleeping habits, and difficulty in overcoming drowsiness are all associated with difficulty in coping with irregular work schedules. Many people opt out of shift working because of these symptoms. [3]

Sleep disturbance

Disturbed sleep is the commonest effect of shift work on health, and shift workers report more sleep disturbances than day workers. [4] These effects vary depending on the shift timing but normally clear within two to three days of finishing shift work and there is no clear indication that long-term shift work results in chronic sleep problems. Night work is characterised by increased subjective and objective sleepiness, and studies frequently report full-blown sleep during night shift working, particularly in the early morning. After a night shift there are between two and four hours loss of REM sleep and it usually takes two nights of sleep after the last night shift before normal sleepiness is restored. Importantly, shift workers are more tired when driving to and from home than non-shift workers.

Other health effects

Gastrointestinal disorders are more common in shift workers, who complain of pain and alteration in bowel habit. There is strong evidence linking shift work to peptic ulcer disease, and rather strong evidence linking shift work to coronary heart disease. [5] Potassium, uric acid, glucose, cholesterol, and total lipids are all increased during night work but return to normal during day work, although the evidence for a link to diabetes is inconclusive. There is rather strong evidence in support of an association between shift work and pregnancy outcome in terms of miscarriage, low birth weight, and preterm birth (see box 1). There is no evidence that night work increases the risk of cancer or that shift work affects longevity.

Effects on performance and safety

In addition to its effects on health, shift work affects functioning and therefore efficiency and safety. [6] Alertness, performance, and metabolism all reach a nadir in the early morning and are at their peak (acrophase) 12 hours later. Multiple studies of practical ability and efficiency have shown significant dips between 10 pm and 6 am, with a trough at 3 am. A number of incidents, such as those at Bhopal, Three Mile Island, Chernobyl, and the Rhine and Exxon Valdez chemical spillages, all occurred at night.

Risk of injury is 30% higher on night shift compared with morning shift and is highest in the first two to three hours; the risk then increases over successive night shifts so that the fourth night shift carries 36% more risk than the first. With extended working hours, risk increases more or less exponentially and in the 12th hour of work it is twice what it was during the first eight hours. The risk of injury is also increased by not taking breaks and rises linearly and substantially with time from the last break; there is twice the risk of injury 90 minutes after the last break compared with immediately after a break.

How to protect yourself

If you want to minimise the effects of shift work on your health and performance, consider the design of your shift and take breaks, naps, and, possibly, melatonin.

The healthiest shift

The best rotating shift system is fast forward rotation, for example, two mornings, two afternoons, and two nights. [7] The worst is a backward rotation of a week of nights, a week of afternoons, and then a week of morning shifts. The optimal time for shift changeover is 7 am. There are good arguments for women to avoid shift work during pregnancy. [5]

When and what to eat

When working nights you should take your main meal break between midnight and 1 am, when a protein or health food meal should be taken, followed by a shorter break between 3 am and 4 am (see box 2). Exercise, adequate light levels, a cool workplace, music, and opportunities to interact with colleagues all enhance alertness on night shifts. The jury is still out on bright light exposure. [8]

Take power naps

Napping is thought to be the most effective countermeasure against sleepiness at work. Several studies have shown that “cockpit naps” (half an hour to two hours) taken during the first night awake counteract the profound fall in alertness around the circadian trough during the early morning. There is a period of impaired alertness (sleep inertia), however, lasting five to 15 minutes after awakening, which can have implications for doctors who have emergency responsibilities.

Melatonin might help you sleep better

Although there is good evidence that melatonin prevents jetlag after eastward travel, the evidence for sleep enhancement after night work is less solid. Taking 0.5 mg to 5 mg of melatonin before going to sleep may enhance sleep quality, [9] but it does little to improve alertness during shift work.

Keep fit, don't smoke, and use earplugs

After shift work, sleep is made easier if noise and light are reduced (for example, by using earplugs or blacking out windows with plastic) as well as by avoiding caffeine, smoking, alcohol, and sleeping pills. Good physical fitness and proper sleep hygiene can favour tolerance to shift work because they increase performance efficiency, lessen fatigue, and improve recovery mechanisms.

Training and assessment

Some companies offer training sessions for shift workers. These sessions deal with circadian rhythms, sleep disorders, impact on family and social life, alertness strategies, safe driving, nutrition, physical activity, and coping with stress. Shift workers are entitled to undergo a free health assessment before their assignment to night work and thereafter at regular intervals; this is normally implemented using questionnaires, which should be administered every three years for those under the age of 45 and every two years for those who are older. If this isn't happening in your corner of the NHS, ask why.

John Hobson editor Occupational Medicine, London NW1 4LB ( John.Hobson@mpcg.co.uk)