The night shift is a hidden cost that affects millions of workers, from junior doctors to lorry drivers, who keep the country running while everyone else sleeps. The scientific evidence about the toll of night shifts on health is increasingly difficult to ignore, with links to heart attacks, strokes, cancer, mental illness, and potentially even memory loss. Now, scientists are exploring whether changing how we sleep can play a role in mitigating these ill-effects, and potentially alleviate the ill-effects of disrupted nights. One surprising theory is that splitting sleep into two separate blocks - rather than attempting to force one long stretch during the day - may be the most effective sleep pattern for people working through the night.
The strain of shift work becomes easier to see when considering the biological processes that occur during sleep. Sleep is not just about being tired, but about repeatedly disrupting a system that's doing far more behind the scenes than many people realize. One remarkable discovery is that while we sleep, the brain cleans itself through the glymphatic system, which washes away waste products that accumulate during waking hours. Disruption of this system has been linked to an increased risk of dementia, with proteins like amyloid and tau accumulating in the brains of people with Alzheimer's disease.
A Swedish study of more than 13,000 shift workers found that shift work in mid-life was associated with a 36% higher risk of dementia, with the risk rising the longer someone had worked shifts. This highlights the importance of sleep in maintaining overall health and preventing chronic diseases. The study also found that disrupted sleep raises the stress hormone cortisol, which promotes insulin resistance and increases the risk of heart disease.
The World Health Organization's International Agency for Research on Cancer (IARC) has classified night shift work as "probably carcinogenic to humans," citing evidence for links to breast, prostate, colon, and colorectal cancers. This may be due to the disruption of the body's circadian system, which alters the timing of melatonin production and reduces vitamin D levels, leading to chronic low-level inflammation.
Despite these concerns, researchers are exploring potential solutions. Dr. Line Victoria Moen is investigating whether a planned nap may be part of the answer. Her research found that many shift workers sleep in two distinct blocks, from nine in the morning until one, then again in the afternoon before the next shift. This pattern, known as biphasic sleep, may be a more natural rhythm, even if the biological reasons for it are still debated.
The dearth of evidence around biphasic sleep is surprising, and Moen's research aims to develop clear clinical guidelines that might help shift workers and others with disrupted sleep patterns. Napping during shift work has been shown to reduce sleepiness and improve alertness, and studies of healthcare workers suggest that even a 20-to-50-minute nap during or after a shift can improve focus and reduce drowsy driving on the way home.
In conclusion, the night shift is a hidden cost that affects the health and well-being of millions of workers. While the scientific evidence is still evolving, it is clear that disrupted sleep patterns can have significant implications for overall health. By exploring potential solutions like biphasic sleep and napping, we may be able to mitigate the ill-effects of night shifts and improve the quality of life for shift workers.
