Cancer, depression and obesity risks for night shift workers higher because of disruption to body clocks
Nobel Prize in Medicine winners’ research into circadian rhythm shows how ignoring or trying to change your body’s day/night cycle can have serious effects on your health
Messing with your body’s clock is dangerous business, in fact it could make you sick – or worse.
The inner timekeeper dubbed the “circadian clock”, governs the day-night cycle that guides sleep and eating patterns, hormones and even body temperature.
It is important enough that the Nobel Prize in Medicine was awarded on Monday to three US scientists whose work illuminates the fundamentals of how it ticks.
The trio identified genes that regulate the clock, and the mechanism by which light can synchronise it.
Yet humans have a long history of overriding the circadian-driven need for sleep, says Russell Foster, a professor of circadian neuroscience at Oxford University – the most obvious example being night work.
Such tinkering can have serious consequences, ranging from impulsive behaviour to life-threatening conditions such as obesity and cancer, the experts say.
Just look at the poor health records of shift workers such as nurses or factory labourers.
The World Health Organisation has already raised the red flag, with a 2007 report noting that “circadian disruption” is “probably carcinogenic”.
The trouble is that the human body never really adapts to operating outside the normal cycle of working by day and sleeping at night.
Like everyone else, shift workers’ biological clocks are set by the rising and setting of the sun – not their work schedule.
“There is no medicine in the world that allows you to ... speed up or slow down your body clock,” says Claude Gronfier, a neurobiologist at France’s Inserm research institute.
When workers force themselves to stay awake they trigger the release of stress hormones such as cortisol. It may keep you on your feet, but it comes at a cost.
For example, cortisol works to suppress the immune system and in the long run can make you more susceptible to a range of diseases, including cancer.
Such a lifestyle also opens one up to eating outside normal times, when the body’s metabolism might be lower and the calories are more likely to be converted into fat instead of being burned up.
“You’re raising your heart rate, your blood pressure and insulin levels at a time that you would not ordinarily do that,” says Hugh Piggins, a neuroscience professor at the University of Manchester. “Your body is basically not ready for it and you’re giving it a bit of an insult.”
Even short-term disruptions of the circadian clock can wreak havoc on your body. Just think jet lag.
Flying from Paris to Los Angeles puts travellers back in time by nine hours, disrupting eating and sleeping patterns.
The results can be blunted interaction with the world and a lack of empathy, complex thinking and even clear memories.
In such a state, people can do “overly impulsive things – jump a red traffic light and fail to see the consequences of actions,” says Foster.
Circadian dysfunction has been linked to depression, bipolar disorder and problems with cognitive function, memory formation and even some neurological diseases.
Over the past two decades, scientists have been studying how the timing of administering a medicine can affect how well it works.
Already they have found that changing the timing can reduce the toxicity of some compounds.
“Now we are moving to the exciting stage where we can start translating some of this knowledge into understanding what happens when these systems go wrong and more importantly to develop new therapeutic interventions,” says Foster.