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 is increasingly difficult to ignore, with links to heart attacks, strokes, cancer, mental illness, and possibly even memory loss. Now, scientists are exploring whether changing how we sleep can play a role in mitigating the toll of night shifts and potentially alleviate the ill-effects of disrupted nights. One surprising theory is that splitting sleep into two separate blocks may be the most effective sleep pattern for people working through the night.
Sleep is a pillar of our health, and the strain of shift work becomes easier to see when we consider the biological processes that occur during sleep. The brain cleans itself while we sleep, and disruption to this process can lead to the accumulation of toxins, including proteins associated with Alzheimer's disease. A Swedish study 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.
There are also tentative but growing indications of how sleep disturbance might increase the risk of heart disease. Disrupted sleep raises the stress hormone cortisol, which promotes insulin resistance and pushes the body toward a diabetic state. The World Health Organization's International Agency for Research on Cancer has classified night shift work as 'probably carcinogenic to humans', citing evidence for links to breast, prostate, colon, and colorectal cancers.
For those who have little choice but to disrupt their sleep, researchers are beginning to pinpoint what might actually help. One study found that shift workers who slept in two distinct blocks, from nine in the morning until one, then again in the afternoon before the next shift, had a more natural rhythm. This pattern, known as biphasic sleep, has been linked to reduced sleepiness and improved alertness, and may be a more natural rhythm for humans.
The eventual aim of this research is to develop clear clinical guidelines that might help shift workers and others with disrupted sleep patterns. The study of biphasic sleep is still in its early stages, but it has already shown that existing research on the topic is fragmented, with no agreed definition of what constitutes biphasic sleep. However, the potential benefits of this research are clear, and it may help to alleviate the hidden cost of the night shift for millions of workers.
