Understanding the negative effects of night work and how to mitigate them

Article Information

Author: Pallab Ghosh, Role: Science Correspondent

Published: 3 hours ago

Reading time: 9 minutes

It is 4 a.m., and the hospital ward is quiet. A young doctor has been on her feet for nine hours; she feels exhausted, her muscles ache, and her eyes are strained. Yet, when she finishes her shift at 6 a.m. and finally returns home, she finds it extremely difficult to sleep.

Her biological clock—shaped by hundreds of thousands, perhaps millions, of years of evolution to regulate human vital processes according to sunrise and sunset—insists that it is morning, time to wake up, and time for alertness and activity. No amount of darkness, earplugs, or blackout curtains can completely silence that clock.

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This is not a personal failing, but a collision between her work demands and one of the deepest biological mechanisms in the human body. It is a phenomenon that repeats, unseen, in the lives of millions of shift workers—including nurses, paramedics, engineers, truck drivers, and factory workers—who keep working to ensure the wheels of life continue to turn while others are fast asleep.

Caption: Night shift workers find it extremely difficult to sleep.

It has become hard to ignore the mounting scientific evidence regarding the high price workers pay for this ongoing battle with their biological clocks and modern lifestyles. The consequences range from heart attacks and strokes to cancer, mental health issues, and perhaps even the loss of cherished memories.

Currently, scientists are beginning to explore whether changing sleep patterns could help mitigate the damage caused by night shift work, and potentially alleviate the negative effects of sleep disruption. Their studies are also testing a surprising theory: that splitting sleep into two separate periods, rather than trying to force the body to sleep for one continuous block, might actually be the most effective sleep pattern for those who work at night.

Caption: A group of workers on a night shift.

The cost of shift work

To understand the impact of shift work on the body, it is worth looking at what recent research indicates about sleep itself. Sleep performs functions that go far beyond just providing the brain and body with a rest.

When we sleep, the brain consolidates the day's memories, processes emotions, and solves problems that eluded us during waking hours. Sleep also strengthens immune defenses and repairs muscle tissue.

Professor Russell Foster, a sleep research scientist at the University of Oxford who has dedicated his career to studying the neurobiology of the brain during sleep, says: "Sleep is a fundamental pillar of our health, just like diet and exercise, so we must pay special attention to controlling and regulating it."

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In light of this, the scale of the burden imposed by shift work becomes clear. It is not just about feeling tired; it may involve the frequent disruption of a vital system that performs hidden functions far exceeding what most people realize.

One of the most prominent discoveries in recent years is that the brain performs a self-cleaning process during sleep. Deep within the gray matter, there is a drainage network known as the "glymphatic system," where fluids flow through tiny channels alongside blood vessels in the brain to wash away and remove waste that accumulates during waking hours.

So, what happens to these toxins when sleep is disrupted?

Professor Hugh Markus, a neurologist who leads the Stroke Research Group at the University of Cambridge, has begun to answer this question.

Markus and medical student Yutong Chen analyzed brain scans of more than 40,000 people. Data was drawn from a massive database of health records and medical imaging collected over more than ten years in the "UK Biobank." All these individuals were healthy at the time of the examinations.

The researchers found that they could identify people whose drainage systems were underperforming. More importantly, they discovered that individuals who experienced the greatest dysfunction in their drainage systems were significantly more likely to develop dementia years later, according to Markus.

Markus says: "Disruption of this flow played an important role in predicting who would develop dementia, within large numbers of the general population."

Caption: When we are asleep, our brain is consolidating the day's memories.

Among the waste products removed by this system are proteins known as "amyloid and tau," which are deposits that accumulate in the brains of Alzheimer's patients. A single night without sleep leads to a noticeable rise in amyloid protein levels in the fluid surrounding the brain. If this happens year after year, the consequences are worrying.

A Swedish study conducted by researchers at the Karolinska Institute, which tracked more than 13,000 shift workers (including night shift workers) over a period of up to 41 years, revealed that shift work in midlife is associated with a 36 percent increased risk of dementia, with the risk increasing the longer a person spent working in shift patterns.

Foster is careful not to overstate this relationship, saying: "We cannot say that lack of sleep causes dementia, but if a person is predisposed to developing it, lack of sleep is a potential risk factor."

Markus's data shows a potential correlation, but he cautions that it is still just a hypothesis at this stage, and there are likely many other factors at play.

Does adjusting sleep habits reduce your exposure to diseases? How so?

He adds: "Sleep is important, but there are also important factors like blood pressure, smoking, and diabetes. What is not usually mentioned is the scale of the risk associated with Alzheimer's disease resulting from these factors, which are things we can actually take action to address."