Night work accounts for approximately 151% of total work in industrialized countries. It affects diverse sectors ranging from transportation to healthcare, the food industry, and many others. However, night work is not without risk to cardiovascular health. Several studies have linked night shifts to a higher risk of heart disease.
The cause is circadian desynchronization, meaning the body's central circadian clock is no longer synchronized with the wake-up and sleep cycles. But meal timing could be one of the keys to reducing these negative effects. A recent study published in the journal Nature Communications shows that in night workers who only eat during the day, and therefore do not eat at night, the heart seems to be protected from the negative effects of night shifts.
It is too early to say whether daytime meals truly negate the negative effects of night work. But the work carried out at Mass General Brigham in the United States are moving in the right direction, even though they were not conducted directly on night workers. To do this, 20 participants underwent a two-week experiment, during which they were all kept in an environment devoid of natural light and external cues about the time of day. There was no dawn, no access to watches or electronic devices. These conditions made it possible to isolate the effects related to circadian rhythm from other factors that could disrupt the experiment.
Read alsoHow Circadian Rhythms Regulate Our Health
A very strict monitoring protocol
The participants first followed a "constant routine protocol," a method used in circadian rhythm research to control for external variables such as sleep, light, or physical activity. During this phase, they remained awake for 32 hours in dim light, maintained the same posture, and ate snacks every hour. After this phase, they began simulating night shift work. While one group ate during both the night and day, the other ate only during the day. To eliminate all variables, even naps were taken at the same time in both groups.
The control group was not suddenly switched to sleeping during the day and waking at night, but was shifted gradually, so that their internal circadian clocks were gradually desynchronized. Each day, the participants' sleep-wake cycle was shifted by four hours until the rhythm between the two groups was 12 hours apart, with one group working during the day and the other at night. We were thus able to reproduce different scenarios of night shift work until the difference was maximal.", tells Science and Future Dr. Frank Scheer, neuroscientist and researcher at Harvard University.
Read alsoNight work increases mortality risk
Altered nervous system and inflammation levels
Several indicators of cardiovascular risk were observed during the experiment, including blood pressure, activity of the autonomic nervous system (which regulates functions such as heart rate, breathing or digestion) as well as plasminogen activator inhibitors type 1 (PAI-1, a protein that can increase the risk of blood clots).
“ In people who ate both day and night, the parasympathetic nervous system was less activated, which has a protective effect on the body. (It is this system that Slows heart rate and reduces blood pressure. It stimulates the digestive tract to digest food and eliminate waste. The energy from digested food is used to restore and build tissues, editor's note). The “fight-or-flight” response (“fight or flight response”), which regulates stress in the face of danger, was also disrupted. Finally, C-reactive protein (CRP), which plays a role in inflammation, was also higher", explains Dr. Scheer. But in those who ate only during the day, these variables remained stable. This was despite the fact that both groups ate the same foods at the same time.
However, this research has several limitations, such as a very small sample size and a short experimental duration. Given these parameters, it is impossible to draw conclusions about the long-term effects of night work on cardiovascular health. The team is currently conducting a more realistic follow-up study, with a protocol closer to the rhythm of real night shift workers. This time, they also want to take into account the effects of genetics to explain the differences between participants.
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