At 4.02am on 2 November 1892 near Thirsk railway station in Yorkshire, an express train crashed into a goods train. Ten people were killed and 39 injured. Nearly 100 years later, at 1:23am on 28 April 1986, the No 4 reactor at the Chernobyl Nuclear Power Plant exploded, killing two people instantly followed by multiple deaths from radiation. Highly radioactive fallout was sent into the atmosphere and the long-term cancers are still being assessed. Understanding how these seemingly unrelated tragedies are connected requires an understanding of biological time.
Our lives are ruled by time. But the alarms that drive us out of bed in the morning or tell us that we are late for a meeting are recently-arrived chronometers. Life answers to more ancient beat that probably started to tick early in evolution. Embedded within our genes are the instructions for a biological or “circadian clock” that regulates our sleep patterns, alertness, mood, physical strength, blood pressure and much more. Normally we experience a 24 hour pattern of light and dark, and this signal is used to align our day to the Earth’s rotation. The clock is then used to anticipate this rotation and fine tune physiology and behaviour in advance of the changing conditions. Temperature, blood pressure, cognitive performance all decline in anticipation of sleep. Before dawn, these processes are slowly reversed in anticipation of the new day.
The daily cycles of sleep and waking are the most obvious of these rhythms. While asleep we don’t eat, drink, make money or have sex. Such apparent pointlessness has relegated sleep to a lowly position on our list of priorities. At best, we grudgingly tolerate sleep and at worst we regard it as an illness that needs a cure. Such attitudes are not only wrong, but dangerous.
Although sleep may be the suspension of most physical activity, the brain is consolidating memories and solving problems; it coordinates the removal of toxins; promotes cell division and tissue repair; and rebuilds metabolic pathways. In short, without sleep our performance and health deteriorate rapidly.
Our species has declared war on the night and sleep has been the victim. The unintended consequences of cheap electric light are twofold. More light at night, combined with entertainments including social media, have eroded sleep time by up to two hours every night. On top of this, many of us are trying to sleep at the wrong time. Night shift workers work when they are sleepy and try to sleep when they are not. The body clock fails to adjust to the nocturnal regime and remains synchronised to the natural light/dark cycle.
Shortened sleep, along with working against biological time, has been linked to multiple health problems. These include lapses in attention and uncontrollable micro-sleeps; impulsivity and loss of empathy; memory impairment and reduced creativity; immune suppression; higher risks of infection and cancer; increased cardiovascular disease, type two diabetes; weight gain; and the susceptibility to depression, anxiety and mood instability are all associated with disrupted sleep.
In our quest for instant gratification, it is unlikely that we are going to stop doing what we like when we like. However, understanding the consequences of bad sleep will surely help us to reprioritise sleep. Perhaps one day, the self-inflicted tired will be viewed with the same contempt as smokers huddled outside a building. Employers need to recognise that employees with disrupted sleep will be less productive and more likely to become ill. Why not introduce higher frequency health checks and provide advice for those at risk? As night shift workers are more likely to have heart disease, type two diabetes and be obese, why not provide food that reduces these risks? Finally, why not use emerging technologies to alert an individual that they are falling asleep both in the workplace and during the drive home?
So what happened at Thirsk railway station in 1892 and Chernobyl in 1986? These disasters, and many other like them, were linked to excessive tiredness, people working at the wrong biological time, and a break-down in procedure. Tiredness and circadian disruption do not cause such tragedies; they simply make them much more likely. James Holmes was the signalman at Thirsk. The day before the crash he had been awake for 36 hours, caring for his daughter who subsequently died, trying to find a doctor and looking after his grief-stricken wife. He reported to the stationmaster that he would be unable to work the next night, but no replacement was sent and he was forced to do his shift. Holmes fell asleep, and forgot that the goods train was on the line when he allowed the express through. After the crash, Holmes was charged with manslaughter and found guilty, but given an absolute discharge. The railway company was blamed for ignoring Holmes, and for failing to use procedures that would have detected he had fallen asleep.
Professor Russell Foster CBE, FRS is Professor of Circadian Neuroscience, Chair of the Nuffield Laboratory of Ophthalmology, Director of the Sleep and Circadian Neuroscience Institute and Fellow of Brasenose College at the University of Oxford, and co-author of the new book “Circadian Rhythms: A Very Short Introduction”.
Russell will give the keynote speech “Sleep – Freedom to Think” at the BBC Radio 3 Free Thinking Festival at Sage Gateshead on Friday 17 March, broadcast that day at 10pm on BBC Radio 3
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