Tag: shift work

Categories : Cardiovascular Disease Diet and NutritionTags : Leave a comment

Daytime-only Meals Could Protect People from the Heart Risks of Shift Work

On By ModernMedia
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A new study from Mass General Brigham suggests that eating only during the daytime could help people avoid the health risks associated with shift work. Results are published in Nature Communications.

“Our prior research has shown that circadian misalignment – the mistiming of our behavioral cycle relative to our internal body clock – increases cardiovascular risk factors,” said senior author Frank A.J.L. Scheer, PhD, a professor of Medicine at Brigham and Women’s Hospital. “We wanted to understand what can be done to lower this risk, and our new research suggests food timing could be that target.”

Animal studies have shown that aligning food timing with the internal body clock could mitigate the health risks of staying awake during the typical rest time, which prompted Scheer and his colleagues to test this concept in humans.

For the study, researchers enlisted 20 healthy young participants to a two-week in-patient study at the Brigham and Women’s Center for Clinical Investigation. They had no access to windows, watches, or electronics that would clue their body clocks into the time. The effect of circadian misalignment could be determined by comparing how their body functions changed from before to after simulated night work.

Study participants followed a “constant routine protocol,” a controlled laboratory setup that can tease apart the effects of circadian rhythms from those of the environment and behaviours (eg, sleep/wake, light/dark patterns). During this protocol, participants stayed awake for 32 hours in a dimly lit environment, maintaining constant body posture and eating identical snacks every hour. After that, they participated in simulated night work and were assigned to either eating during the nighttime (as most night workers do) or only during the daytime. Finally, participants followed another constant routine protocol to test the aftereffects of the simulated night work. Importantly, both groups had an identical schedule of naps, and, thus, any differences between the groups were not due to differences in sleep schedule.

The investigators examined the aftereffects of the food timing on participants’ cardiovascular risk factors and how these changed after the simulated night work. Researchers measured various cardiovascular risk factors, including autonomic nervous system markers, plasminogen activator inhibitor-1 (which increases the risk of blood clots), and blood pressure.

Remarkably, these cardiovascular risk factors increased after simulated night work compared to the baseline in the participants who were scheduled to eat during the day and night. However, the risk factors stayed the same in the study participants who only ate during the daytime, even though how much and what they ate was not different between the groups—only when they ate.

Limitations of the study include that the sample size was small, although of a typical size for such highly controlled and intensive randomised controlled trials. Moreover, because the study lasted two weeks, it may not reflect the chronic risks of nighttime versus daytime eating.

A strength is that the study participants’ sleep, eating, light exposure, body posture, and activity schedule were so tightly controlled.

“Our study controlled for every factor that you could imagine that could affect the results, so we can say that it’s the food timing effect that is driving these changes in the cardiovascular risk factors,” said Sarah Chellappa, MD, MPH, PhD, an associate professor at the University of Southampton, and lead author for the paper.

While further research is necessary to show the long-term health effects of daytime versus nighttime eating, Scheer and Chellappa said the results are “promising” and suggest that people could improve their health by adjusting food timing. They add that avoiding or limiting eating during nighttime hours may benefit night workers, those who experience insomnia or sleep-wake disorders, individuals with variable sleep/wake cycles, and people who travel frequently across time zones.

Source: Mass General Brigham

Categories : HospitalsTags :

Study Shows that Not Everyone can Adjust to Shift Work

On By ModernMedia
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A new study of French hospital workers have challenged the widely held belief that shift workers adjust to the night shift over time, using data drawn from wearable sensors.

By monitoring groups of the hospital workers working day or night shifts during their working and free time, the researchers have shown that not only does night work significantly disrupt both sleep quality and circadian rhythms, also that workers can experience such disruption even after years of night shift work.

Their findings, reported in eBioMedicine, are the most detailed analysis of the sleep and circadian rhythm profiles of shift workers yet attempted, and the first to also monitor body temperature. This key circadian rhythm is driven by the brain pacemaker clock, and coordinates the peripheral clocks in all organs.

In addition, the research demonstrates the value of telemonitoring technology for identifying early warning signs of disease risks associated with night-shift work opening up intervention opportunities to improve the health of workers.

The study compared 63 night-shift workers, working three or more nights of 10 hours each per week, and 77 day-shifters alternating morning and afternoon shifts at a single university hospital near Paris. Both groups wore accelerometers with chest surface temperature sensors throughout the day and night for a full week.

The accelerometer measured movement intensity and served as an estimate for participants’ sleep duration, how regular were their circadian rhythms, and whether that sleep was disrupted by movement. Patterns in the chest surface temperature gave a further indication of the participants’ circadian rhythm, which coordinates rest-activity phases, varying core body temperature, and an array of other bodily rhythms.

Analysis of interruptions to sleep and rhythmic variations in core body temperature showed that night-shift workers had less than half the median regularity and quality of sleep of their day-shift colleagues. 48% of the night-shift workers had a disrupted circadian temperature rhythm.

Using information from questionnaires on the participants’ chronotypes, they also found that the centre of sleep for those working the night shift didn’t correlate with their respective chronotype, ie their morningness or eveningness orientation. This meant they were not sleeping in synch with their internal clocks.

Even workers with years of being on night shifts still showed these negative effects on circadian and sleep health. The more years of night work they had, the more severe the circadian disruption – contradicting widely held assumptions about night work adaptation.

This helps explain why previous studies have shown an association between disrupted circadian rhythms with long term health risks, such as cancer and cardiovascular disease.

Professor Bärbel Finkenstädt from the University of Warwick Department of Statistics said: “There’s still an assumption that if you do night work, you adjust at some stage. But you don’t. We saw that most workers compensate in terms of quantity of sleep, but not in terms of quality during the work time.”

Dr Julia Brettschneider of the University of Warwick Department of Statistics said: “I think there’s a misunderstanding that night shift work is just an inconvenience, whereas it can be linked to serious health risks. We can’t avoid shift work for many professions, like healthcare workers, so we should be thinking about what can be done in terms of real-world adjustments to improve working conditions and schedules of shift workers. A better understanding of the biological mechanisms helps to find answers to this question.

“Together with our PhD student Yiyuan Zhang, we have developed a statistical analysis framework that enables the discovery of patterns and predictive factors in the complex data sets created by wearable tech.”

Professor Francis Lévi from Université Paris-Saclay further added: “Nearly 20% of the night workers could not even adjust their circadian rhythms during their free time, with the severity of impairment tending to increase with the number of years of night work. The telemonitoring technology, and analysis methods we have set up make it now possible to objectively evaluate circadian and sleep health in night workers in near real time, and design prevention measures for individual workers whenever necessary.”

In future research, the team may look at more long-term outcomes, such as diseases such as cancer that have been linked to circadian disruption.

Source: University of Warwick