Randomized trial simulating shift work
For the study, the researchers recruited 19 participants, including 12 men and 7 women with an average age of 26.5 years old.
To prepare for the study, the participants maintained a fixed bedtime of 8 hours for 2 weeks. They then underwent a 14-day lab stay.
After several days of acclimatizing to the lab and providing baseline measurements, the participants underwent a forced synchrony (FD) protocol in dim light for 4 28-hour “days.”
The protocol allowed participants to gradually shift to a “nighttime work schedule.” By the fourth day, they were misaligned from the first day by 12 hours.
During the FD phase of the study, participants were randomly assigned to receive meals either in the daytime alone or during the daytime and nighttime together, which is typical for night workers.
Other conditions remained the same among the participants, including caloric and macronutrient intake, physical activity, sleep duration, lighting conditions, and night work.
The researchers assessed participants’ depression-like and anxiety-like mood states every hour during the FD days
After analyzing the results, the researchers found that those who ate during the night and day had a 26.2% increase in depression-like mood, and a 16.1% increase in anxiety-like mood, compared to the beginning of the study.
By comparison, those in the daytime eating group experienced no change in levels of depression-like or anxiety-like mood.
By assessing the participants’ glucose and body temperature rhythms, the researchers found that the degree of circadian misalignment was robustly linked to more depression-like and anxiety-like moods.
They further noted that daytime eating only despite mistimed sleep was linked to maintenance of internal circadian alignment.
Effects of meal timing on circadian rhythms
When asked how meal timing might interact with circadian rhythms, collapse Ph.D., from the Department of Nuclear Medicine at the University of Cologne, Germany, and co-corresponding author of the study told MNT:
Our circadian system is composed of a master circadian clock in the brain and peripheral clocks in most tissues throughout the body. While the master clock is synchronized primarily by the daily light-dark cycle, many peripheral clocks are most strongly synchronized (e.g., the timing of food intake).
Therefore, eating meals during the night can cause an uncoupling between peripheral circadian rhythms and the central clock. [For example], the central clock may be on [the] Boston (United States) time zone, while the peripheral clocks are on [the] Cologne (Germany) time zone, Dr. Chellappa added.
This disruption in the circadian alignment between different clocks throughout our body (called internal circadian misalignment) may account for the increased physical and mental health risks among night shift workers who often eat during the night.
– Sarah Chellappa, Ph.D., co-corresponding study author
Impact on mental health
Gregory Nagaland, Ph.D., a clinical psychologist at the University of Kansas Health System, not involved in the study, told MNT that clinicians are aware of the potential for depression and anxiety to produce circadian Dysregulation as patients’ sleep patterns are often disrupted. Dysregulation can produce disconnection from the outside world as an individual perhaps sleeps through commitments only to wake and experience increased depression/anxiety or self-loathing as a result. “This fuels a vicious cycle that exacerbates their experience of depression or anxiety in terms of feeling hopeless or helpless about their situation,” Dr. Nawalanic said.
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