
Shift work – the hidden human costs
Humans are diurnal creatures. Our internal clock is geared for daytime wakefulness and night-time sleep. However, modern civilization has become a 24-hour operation, forcing many people to work night shifts. The amount of shift work has increased dramatically in all industrialised nations during the past 30 years, with up to a quarter of all workers now doing shift work.
Whilst the odd sleepless night will have little or no consequences beyond a bit of fatigue, long-term night shift work is associated with a range of quite serious symptoms and risks. Night shift workers show an increase in irritability, moodiness, irrationality and forgetfulness. Emotional control is reduced, leaving shift workers more prone to ‘losing it’. Surveys have found that more relationships break up with shift workers, with partners claiming all of the above as reasons for the break up. And that is not all, common physical symptoms include sleep-awake problems (problems falling and staying asleep and sleepiness during work), fatigue, reduced concentration, increased susceptibility to infections, and gastrointestinal problems such as ulcers and constipation.
Shift workers also generally have more unhealthy lifestyle behaviours (such as smoking, poor diet, alcohol abuse and lack of exercise), increased stress levels, and a higher incidence of cardiovascular disease and hypertension. They are at increased risk of drug or alcohol addiction, because they frequently rely on such substances to help them sleep.
Circadian (from the Latin ‘circa’ meaning around and ‘diem’ meaning a day) rhythms are based on an internal 24-hour clock and are critical in determining many biological cycles including the sleeping and feeding patterns of all animals and humans. This endogenous biological clock regulates changes in brain wave activity, hormone production, cell regeneration, core body temperature and many other biological processes throughout the 24-hour period.
Circadian rhythms are linked to the cycle of day and night, and are constantly reset or entrained by this cycle. Difficulties in readjusting our biological clocks are primarily responsible for shift work problems, some types of sleep disorders and, of course, jet lag.
The two main ways of measuring the different phases of our circadian rhythms include melatonin production and core body temperature. Melatonin, a hormone, is undetectable during daytime. With the onset of darkness its presence becomes measurable in both blood and saliva around 9 pm. Melatonin prepares us for sleep and cell renewal. Even without shift work, the act of working late into the night with very bright lights and flickering computer screens can adversely affect melatonin production and therefore the quality of our sleep and cell regeneration, with possibly far-reaching health implications.
The average adult’s core body temperature reaches its minimum at around 5 am, roughly two hours before habitual wake-up time. This also happens to be the time (5-7 am) that shift workers often feel the sleepiest, and therefore make the most errors.
Truck drivers have the lowest daily sleep averages of all shift workers. This fact alone should wake us all up. In fact the most important factor in predicting a traffic accident is the duration of a driver’s last sleep period. This research led to the passing of ‘Maggie’s Law’ in the US in 2003, which was the first law to criminalise sleep-deprived drivers. It was named after Maggie McDonnell, who was killed by a driver who fell asleep at the wheel after going without sleep for 30 hours.
Many studies have demonstrated that performance errors increase significantly when continuous work periods exceed 12 hours, in all forms of shift work from drivers and operators of heavy machinery to medical personnel and pilots. Humans need periodic sleep for the restoration of both body and brain and prolonged periods of wakefulness lead to attention lapses; slower reaction times; and reduced cognition, judgement and performance, sometimes by up to 40%.
The aviation industry has long known how sleep deprivation affects performance and therefore accident risk. They have strict regulations regarding the period of continuous work for pilots, as do many other industries. However throughout the world, many shift workers, including medical personnel and truck drivers, continue to exceed these recommended limits on a daily basis, putting themselves and others at risk.
Dr Peter Hauri, in his best-selling book ‘No More Sleepless Nights’ gives the following advice to shift workers:
- Move the rotation of shifts forwards around the clock beginning with the morning shift, followed by the evening and finally the night shift
- Make shift rotation periods as long as possible as this leads to far less stress, sleep problems and daytime sleepiness. Instead of the common weekly shift rotations, three-weekly rotations are recommended
- If you work on a rotating shift try to prepare for the new schedule on your days off by, for example, going to bed a bit later if you are due for an evening shift
- Give yourself time to relax and unwind after work before trying to sleep
- Schedule your sleep time and defend it vigorously
- Make your bedroom as dark (for melatonin production) and sound proof as possible
- Hide the clock and rest quietly if you cannot actually sleep as this gives your body considerable recovery
- Limit consumption of caffeine from coffee, tea, cola drinks and chocolate to the beginning of your shift work, or avoid totally
- Avoid heavy, spicy, or hard-to-digest foods if you are eating in the middle of the night
- Plan some quality time with your family and friends for exercise, relaxation, fun, and catching up. Discuss your situation and needs with your family – support at home is one of the most important aspects of successful shift work adjustment
Light therapy can help people to reset their circadian rhythms to a new schedule in under three days instead of the two weeks it normally takes. This is why jet lagged travellers should spend time in bright light during the day when they need to be awake, and not succumb to the temptation to nap. They will adjust to the new light-day cycle much more quickly.
Finally Hauri advises the importance of a balanced diet and sufficient quantities of the nutrients that play an important part in antidoting stress and fatigue, and promoting uninterrupted, healthy sleep. These include: all the B vitamins, particularly vitamins B3, B6 and B12 and folic acid; vitamin D; calcium; magnesium; zinc; iron and copper. Some of these nutrients are critical for the manufacture of serotonin, the feel good brain neurotransmitter. In addition to mood control, serotonin helps to regulate sleep, body temperature, blood pressure and hormonal activity. It is also needed to make melatonin, the all important sleep hormone.
Shift work is here to stay, but with the right scheduling and nutritional support it is possible to minimise the adverse effects – preserving one’s health, maximising one’s efficiency on the job, and preserving harmonious marital and family relations.