Researchers are investigating “biphasic sleep”—splitting daily rest into two segments—as a potential strategy to mitigate the health risks of shift work. Evidence suggests that chronic disruption of the body’s internal clock, common among night-shift employees, is linked to increased risks of dementia, cardiovascular disease, and certain cancers.
The Physiological Toll of Shift Work
For millions of night-shift workers, the struggle to sleep during daylight hours is not a failure of willpower, but a biological reality. The human body is naturally programmed to remain alert during the day, creating an inherent conflict for those working against their circadian rhythms.
Russell Foster, a sleep scientist at the University of Oxford, emphasizes that sleep is a fundamental pillar of health, comparable to nutrition and exercise, and requires active management. When that management fails due to shift work, the consequences extend beyond mere fatigue. Research indicates that chronic sleep disruption is associated with heart disease, stroke, cancer, and mental health disorders. Furthermore, the World Health Organization’s International Agency for Research on Cancer (IARC) has classified night-shift work as having a probable carcinogenic risk, placing it in a category similar to red meat due to its links to breast, prostate, and colon cancers.
Brain Health and the Glymphatic System
One of the most alarming areas of recent research concerns the brain’s ability to maintain its own hygiene. During sleep, the glymphatic system
—a network of channels deep within the brain’s gray matter—uses fluid to flush out metabolic waste. If this process is repeatedly interrupted, toxic proteins such as amyloid and Tau, which are associated with Alzheimer’s disease, can accumulate.
Hugh Markus, who leads a stroke medicine team at the University of Cambridge, analyzed data from more than thousands of health records in the UK Biobank. The findings suggest that individuals with poor metabolic waste clearance face a significantly higher risk of developing dementia. The correlation is stark: a study by the Karolinska Institute in Sweden, which tracked over thousands of shift workers for 41 years, found that shift work increased the risk of future dementia by 36%. The risk climbed in tandem with the number of years spent in shift-based roles.
Biphasic Sleep as a Potential Intervention
To address these systemic health risks, researchers are looking toward “biphasic sleep”—a pattern where rest is split into two distinct periods. Line Victoria Moen, a researcher at the National Institute of Occupational Health in Oslo, Norway, began studying this pattern among workers in the Arctic Circle. In the summer, the region experiences near-constant daylight, forcing workers to navigate their sleep schedules in an environment where the sun never sets.
Moen’s data revealed that many of these workers do not attempt to sleep in one long block. Instead, they often sleep from 9:00 a.m. to 1:00 p.m., then supplement that rest with a second period of sleep before their evening shift. Historians point out that this is not a modern invention; before the advent of the Industrial Revolution and widespread artificial lighting, humans commonly practiced biphasic sleep.
While current scientific data on the efficacy of split-sleep schedules remains fragmented, the goal is to develop clinical guidelines that reduce "sleep anxiety" among shift workers.
Managing the Biological Clock
Beyond the potential for biphasic scheduling, smaller interventions have shown promise. Research indicates that even short naps—ranging from 20 to 50 minutes—during a shift can improve alertness and reduce the risk of fatigue-related incidents. These strategies are part of a broader effort to provide workers with what Moen describes as a “permission” to align with their body’s natural signals rather than forcing a constant, losing battle against the brain’s internal timing.
As the scientific community continues to explore these patterns, the focus remains on mitigating the physiological stress of night work, which includes elevated levels of the stress hormone cortisol—a factor that can lead to insulin resistance and chronic inflammation. For those currently navigating these schedules, consultation with a healthcare professional regarding sleep hygiene and potential clinical strategies remains the most prudent course of action.
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