The Biological Cost of 24/7 Living

We live in a 24/7 society and the ability we now have to book a holiday in the middle of the night or to manage our finances on a Sunday feels like a luxurious convenience. But none of this convenience comes without a cost and this cost is frequently underestimated.

The provision of 24 hour a day services necessitates increasing amounts of shift work and more work being done during unsociable hours. Nearly a third of workers in America and Europe now work some kind of shift pattern (1) and some estimate that as few as one in four Europeans now work regular daytime hours (2).

We are no different from other animals. We are a product of the wild environment in which we evolved and the world around us has sculpted every detail of our biology. The natural human state is to be active in the day and rested at night and our bodies have elegant biological mechanisms that make us alert and ready for action during the day and drowsy at night.

It is no coincidence that the risk of accidents at work is 60% higher for those who work non-day shifts (3), and that most road accidents occur between two and six o’clock in the morning with almost a third of HGV crashes occurring during this time period even though far less trucks are actually on the road at this time of the night than at other times of day (4).

Our sleep-wake cycle is governed by our circadian rhythms, the rhythmic changes in hormone levels that take place in our bodies all the time. Key to our sleeping patterns are the hormones cortisol, which peaks in the morning when we are supposed to be at our most alert, and melatonin, levels of which rise in the evening to ready us for sleep.

The rhythm is not absolutely fixed but can be altered by various environmental cues known as ‘zeitgebers’ (time givers), chief amongst which is exposure to daylight. Perhaps the commonest example of this re-aligning of our natural rhythms is after long haul flights when our bodies adjust to the new time zone. The experience of jet lag, which can include sleepiness, feeling unwell, disturbed sleep and mood changes, is essentially what many of those who work in variable shift patterns experience all the time.

Shift workers are routinely battling against their own biology and, because of continually changing sleep patterns, shift workers often don’t adapt their circadian rhythms in the same way as those recovering from jet lag. This has all kinds of knock on psychological and physical effects and there is now a recognised diagnosis of ‘shift work sleep disorder’ which affects about 10% of shift workers (5).

This disruption of our hormonal rhythms has been shown to alter the way that the body handles fat, sugar, and inflammation, and this has implications for rates of type two diabetes, obesity, certain forms of liver disease, high blood pressure, heart disease, and strokes (6). Melatonin, in particular, has been found to be important for the process of repairing damaged DNA inside the body’s cells. If left unrepaired, damaged DNA can cause cells within the body to develop into tumours and so shift workers suffer with higher rates of cancer.

Numerous studies have shown increased cancer rates, particularly with respect to breast cancer, amongst those who work on rotating shifts. In 2007 the International Agency for Research on Cancer decided that the evidence was so strong linking shift work to cancer that they categorised shift work as a carcinogen, and the Health and Safety Executive published research in 2010 which asserted that 54% of breast cancer registrations were attributable to shift work (4). One study found that regularly working just three night shifts each month on a long term basis demonstrably increased the risk of breast cancer in women (7).

Just as shift work is bad for your physical health so too is it bad for your mental health. The effect on mental health may be relatively low level, manifest by irritability, feelings of stress, or a general loss of a sense of well-being, but shift work and the poor quality sleep associated with it, has also been shown to be a risk factor for depression, anxiety, bipolar disorder and possibly psychotic illnesses such as schizophrenia (8, 9, 10, 11). We have an epidemic of mental ill-health in this country and, when looking for the root causes of this problem it is without doubt important that we address the rising levels of shift work.

The convenience of 24-hour services and next day delivery is not possible without people working increasing numbers of unsociable hours that force them to work against the biological drives of their body. Convenience feels good when it works in our favour but how many of us are now working in these unhealthy ways for the convenience of others? And at what point does the cost of this convenience become too high?