Struggling with night shifts? Study says your body’s internal clock is to blame

The study explained the connection between the body’s way of adjusting to seasons, to how one can adjust to night shifts.

People who work night shifts often face sleep disruptions. Interestingly, some individuals adapt to schedule changes more easily than others. According to a recent study, published on May 28, 2025 and led by Daniel B. Forger and Ruby Kim from the University of Michigan, the biological systems that help us adjust to seasonal changes may also play a key role in adapting to irregular work hours.

The biological system that help us adjust to changing seasons might be responsible for adjusting to shifting schedules. (Shutterstock)

Findings of the study

The study, published in npj Digital Medicine, stated that our evolutionary programming that can handle seasonal changes is responsible for working against us in the modern world.

The study observed 3,000 medical interns and found a link between seasonal adaptability and sleep schedule disruptions. Those who exhibited greater seasonal variation, such as significant differences in activity levels between summer and winter, struggled more with adjusting to shifting sleep patterns. In contrast, individuals whose step counts remained relatively consistent year-round were better able to cope with night shifts and irregular schedules.

Unable to adjust to changing work shifts? Here's why. (Unsplash)

Study author Ruby Kim from the University of Michigan, in a statement said, “Humans really are seasonal, even though we might not want to admit that in our modern context. Day length, the amount of sunlight we get, it really influences our physiology. The study shows that our biologically hardwired seasonal timing affects how we adjust to changes in our daily schedules.”

The study is a wake-up call

Scientists have long known the importance of an internal clock in humans that connect their biological functions to daylight. Referred to as the circadian rhythm of the body, this internal clock helps in maintaining bodily functions with the timings of day and night. However, this is the first study of its kind to connect the circadian rhythm of the body to changing work shifts.

Study author Daniel Forger from the University of Michigan, added, “A lot of people tend to think of their circadian rhythms as a single clock. What we’re showing is that there’s not really one clock, but there are two. One is trying to track dawn, and the other is trying to track dusk, and they’re talking to each other.”

Note to readers: This article is for informational purposes only and not a substitute for professional medical advice. Always seek the advice of your doctor with any questions about a medical condition.