Cold is a routine part of many occupations, from seafood processing to offshore operations.
At the same time, shift work is known to interfere with the body’s internal timing system, which regulates sleep, hormones and metabolic functions.
Researchers at the National Institute of Occupational Health in Norway (STAMI) set out to investigate whether these two realities intersect more strongly than previously assumed.
According to STAMI researcher Phong Khac Thanh Chau, the project grew from a simple question: Does cold feel different depending on what time it is?
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His doctoral work explored how circadian biology might shape how people experience and tolerate low temperatures.
Field notes from freezing workplaces
To investigate the idea, the research team combined laboratory experiments with real-world observations.
In the lab, mice were monitored for heat production and signs of discomfort at different times of day.
Out in northern Norway, the team followed seafood workers on rotating shifts, taking blood samples, tracking hand temperature and recording symptoms associated with cold exposure.
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Although the two environments could hardly be more different, Phong Khac Thanh Chau says the trend pointed in the same direction.
Workers’ physiological responses, and their reported discomfort, shifted according to the hour of exposure.
Those coming off night duty in particular appeared to recover more slowly, a pattern researchers link to disrupted circadian rhythms.
Timing may matter for the worker's safety
The findings suggest that cold is not merely a physical stressor but an environmental cue that interacts with the body’s internal clocks.
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For people who work outside regular daytime hours, this could mean additional strain on warmth regulation and pain sensitivity.
Phong Khac Thanh Chau believes the insights could inform better scheduling practices and improved protective measures.
Understanding how time of day interacts with cold, he notes, may eventually help workplaces design conditions that reduce discomfort and support healthier recovery for shift-based employees.
Sources: Forskning.no, National Institute of Occupational Health in Norway, and Journal of Occupational Medicine and Toxicology.
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