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Is darkness good for our health?

November 10, 2023
The clocks have changed for winter and, once again, we must become accustomed to shorter days and dark evenings, whether we like it or not.
But despite night falling early, we rarely spend any time in the dark. Cities never sleep, pavements are illuminated by street lamps, and rooms are lit by the dim glow of a phone screen.
Constant light can have detrimental effects on our circadian rhythms, which makes us more likely to suffer from ill health - and thanks to the 24-hour nature of our healthcare system, its workers often feel these effects the most. 

Why is darkness important?

We have acclimatised to 24-hour light. The industrial age transformed cities into beacons of light. Las Vegas can even be seen from space. In fact, about 80% of us live in an area that is bathed in artificial light: a recent report from the London Assembly showed the UK’s capital is 24 times brighter than the darkest region of the South West.

This assimilation has seeped into all aspects of our lives - online shopping is a 24-hour activity; restaurants open at 10pm; television now runs through the night. This world is no longer set up to accommodate our circadian rhythms, and according to research, losing these constraints of day and night can have a profound effect of our heath.

Geologist Michel Siffre’s 1962 cave experiment exposed our biological clocks and our innate need for natural light and darkness. Disturbing these rhythms can significantly affect our metabolism, which reduces our immunity and increases the risk of developing diabetes, obesity, and cardiovascular diseases. Scientists discovered that our bodies can only produce melatonin when it’s truly dark. Melatonin fights diseases such as prostate and breast cancer.

Who is most affected by this lack of darkness?

Sticking to our body’s natural light and dark cycle becomes particularly tricky for those who work long hours or night shifts – like healthcare workers. Disturbed circadian rhythms can promote stress and fatigue, which in turn can have hazardous effects on work, creating errors in the care provided, which negatively affects patients.

The sleeping patterns and work schedules of healthcare shift workers are often in conflict with this light and dark cycle, which instinctually promotes sleep at night. A French study found no matter how long staff members had been working night shifts – weeks, months or years – the body did not adapt. “There’s still an assumption that if you do night work, you adjust at some stage. But you don’t,” said Professor Bärbel Finkenstädt from the University of Warwick Department of Statistics.

Dr Julia Brettschneider, who also worked on the study, added: “I think there’s a misunderstanding that night-shift work is just an inconvenience – it can be linked to serious health risks.”

Can the situation be improved for healthcare workers?

Stretching the boundaries of daytime has repercussions on our world. Animal migration and plant reproduction suffers. Nocturnal insects can’t see their prey. Alterations of the pigmentation in dark-dwelling animals can even determine their sex.

For humans, at its most base, a lack of darkness is certainly affecting the way we sleep. It’s impacting the quality and quantity of our resting hours. We aren’t supposed to live in perpetual illumination – our biological rhythms evolved before artificial light existed.

So, how can we improve the lives of night workers in healthcare, whose evenings are darkness-deprived and drenched in artificial light? The Sleep Foundation has some tips, such as gradual delaying your sleeping pattern, or opting for rotating shifts.

But Dr Brettschneider says it's about investing in more research and implementing realistic constructs around those results. “We can’t avoid night work for healthcare workers, so we should be thinking about what can be done in terms of real-world adjustments to improve working conditions and schedules of shift workers. A better understanding of the biological mechanisms helps to find answers to this question.”

Studies show we develop a fear of the dark from the age of two, and this anxiety ebbs and flows as we age. We remain aware of the terrors that darkness can bring, more alert to crime and wrongdoing. The dark has always had negative connotations – black magic, black death. But we should learn to embrace the dark. Darkness is in everything: it’s integral to poetry, science, medicine, literature, space, our sprawling ecosystem. And, crucially, it’s essential to our wellbeing.