It is four in the morning, and the ward is quiet. A junior doctor has been on her feet for nine hours. She is tired, her muscles are sore and her eyes are straining, but when her shift ends at six in the morning and she finally gets home, she struggles to sleep. Her internal clock, built over millions of years of evolution to tune human biology to the rising and setting of the Sun, is insisting it is morning. No amount of darkness, earplugs or blackout blinds can entirely silence it.
This is not a personal failing. It is a collision between the demands of her job and some of the deepest machinery in the human body. And it is playing out, invisibly, in the lives of more than three million people in the UK who work night shifts — among them nurses, paramedics, engineers, lorry drivers and factory workers, who keep the country running while everyone else sleeps.
“Three million UK night workers face health risks; split sleep may help.”
The scientific evidence about what this relentless battle with our own internal clocks costs them is increasingly difficult to ignore. Studies link night shift work to heart attacks, strokes, cancer, mental illness, and quite possibly the loss of precious memories. Sleep, as Prof Russell Foster, a sleep scientist at Oxford University, puts it, "is a pillar of our health, in the same way we think about diet and exercise. We have to take control of it."
But what is often overlooked is that sleep does far more than give the brain and body a rest. When we sleep, the brain consolidates memories, processes emotions, and solves problems that defied it in the waking hours. It also strengthens immune defences and repairs muscle tissue. One of the most remarkable discoveries of recent years is that while we sleep, the brain cleans itself — deep within the grey matter, fluid runs along tiny channels beside the brain's blood vessels, washing away waste products that accumulate during the day.
Now scientists are beginning to explore whether changing how we sleep can play a role in mitigating the toll of night shifts. Their studies are testing a surprising theory: that splitting sleep into two separate blocks — rather than attempting to force one long stretch during the day — may in fact be the most effective sleep pattern for people working through the night. If proven, it could offer a practical way to alleviate the ill-effects of disrupted nights, though the research is still in its early stages.