Scientists suggest split sleep cycles may help reduce night shift health…
New research suggests that adopting historical biphasic sleep patterns could help night shift workers manage the physical and psychological toll of their schedules. Scientists are now evaluating how splitting sleep into two blocks may improve alertness and long-term health outcomes.
Scientists are increasingly exploring how split sleep cycles — dividing sleep into two distinct blocks rather than one long stretch — may mitigate the health risks associated with night shifts. This approach, rooted in historical patterns of biphasic sleep, is being studied as a potential solution to the profound physiological and psychological toll of working against the body’s natural circadian rhythm.
The human circadian system, governed by the suprachiasmatic nucleus, is designed to align with the sun’s cycle. Night shift work disrupts this alignment, leading to chronic misalignment between the body’s internal clock and external demands. This mismatch has been linked to a range of health issues, including increased risks of dementia, cardiovascular disease, cancer, and mental health disorders. Studies suggest that the glymphatic system, which clears waste products from the brain, operates less efficiently during disrupted sleep, potentially contributing to neurodegenerative conditions like Alzheimer’s. A Swedish study found that mid-life shift work correlated with a 36% higher dementia risk, while the World Health Organization classifies night shifts as “probably carcinogenic to humans.”
Research into sleep patterns reveals that many night shift workers naturally adopt a biphasic rhythm, sleeping in two segments rather than one. Dr. Line Victoria Moen of Norway’s National Institute of Occupational Health, who studied Arctic shift workers, observed that individuals often slept from 9 a.m. To 1 p.m. And then again in the afternoon. This pattern, she notes, mirrors historical sleep practices before artificial lighting, when humans commonly slept in two halves. “The default is almost certainly not a single block,” says Prof. Russell Foster of Oxford University, who cites experiments showing that without instruction, people exposed to extended darkness naturally split their sleep.
Split sleep may offer practical benefits for shift workers. A 20- to 30-minute nap during a shift can improve alertness and reduce fatigue, while maintaining a consistent daytime sleep window helps stabilize the circadian rhythm. However, challenges remain. Daytime sleep is often fragmented and less restorative due to environmental factors like light and noise. Prof. Hugh Markus of the University of Cambridge warns that while disrupted sleep may correlate with dementia risk, other factors like vascular health also play significant roles. “Sleep matters, but so do blood pressure, smoking, and diabetes,” he emphasizes.
The mental health toll of night shifts is equally severe. Chronic circadian misalignment is tied to depression, anxiety, and cognitive decline. Studies show that long-term shift workers experience slower processing speeds and memory deficits that persist even after leaving night shifts. The neurolaunch.com article highlights how circadian disruption alters brain chemistry, increasing amygdala reactivity and weakening prefrontal cortex function, making individuals more prone to stress and emotional dysregulation. “Shift work sleep disorder,” a recognized condition, affects 10–38% of workers, with symptoms including insomnia and excessive daytime sleepiness.
Experts recommend strategies to mitigate these risks. Employers are urged to adopt forward-rotating schedules, provide access to mental health resources, and create conducive sleep environments. For individuals, consistent sleep timing, light management, and napping are critical. Dr. Moen advocates for “permission, backed by science,” to embrace biphasic sleep rather than fighting the body’s signals. “A good nap in the afternoon will help,” she says.
As research progresses, the need for systemic support becomes clear. Shift workers face a dual burden: the physical strain of disrupted sleep and the psychological weight of social isolation and stigma. While split sleep cycles offer a promising avenue, broader changes, policy reforms, workplace accommodations, and public awareness, are essential to address the hidden costs of night shifts. For millions of workers, the path to better health may lie not in resisting their biology, but in learning to work with it.
