Seasonal sunlight still shapes human sleep

Summary: Despite modern lighting and lifestyle, human sleep habits remain deeply influenced by seasonal changes in sunlight. New research reveals that our circadian rhythms are following daylight move through the seasons, an impact on mood, alignment of sleep and overall health.

Using data from medinel residents and genetic samples, the study revealed that the internal clocks of individuals are adjusted at dawn and twilight, and that some people can be more genetically sensitive to these changes. This double -blocking mechanism suggests a deeper physiological seasonality and opens up new ways to understand disorders such as seasonal emotional disorder.

Key facts:

• Double circadian clocks: Humans have two internal clocks – one follows dawn, the other twilight.
• Genetic sensitivity: Some people are more vulnerable to sleep disturbances in the quarter -season.
• Health implications: Disalizing with circadian rhythms can affect mood, metabolism and cardiovascular health.

Source: Michigan University

It is tempting to think that with our fancy electric lights and our interior rooms, humanity has evolved beyond the natural influence of sunlight with regard to our sleep routines.

But new research from the University of Michigan shows that our circadian rhythms are always wild in the soul, according to seasonal changes in daylight.

“Humans are really seasonal, even if we do not want to admit that in our modern context,” said study author Ruby Kim, postdoctoral assistant professor of mathematics.

“The duration of the day, the amount of sun we get, it really influences our physiology. The study shows that our biologically wired seasonal timing affects the way we adapt to changes in our daily hours. ”

This observation could allow new ways to probe and understand seasonal emotional disorder, a type of depression linked to seasonal changes. It could also open up new areas of survey in a range of other health problems linked to the alignment of our sleep schedules and our circadian clocks.

For example, researchers – including the main author of the study, Daniel Forger – have previously shown that our moods are strongly affected by the way our sleep hours align with our circadian rhythms.

“This work shows a lot of promises for future results,” said Kim about the new study published in the journal NPJ Digital Medicine.

“This can have deeper implications for mental health problems, such as mood and anxiety, but also metabolic and cardiovascular conditions.”

Research has also shown that there is a genetic component of this seasonality in humans, which could help explain the big differences in the strength of people affected by day length changes.

“For some people, they could be better suited, but for other people, it could be much worse,” said forge, professor of mathematics and director of Michigan Center for Applied and Interdisciplinary Mathematics.

The exploration of this genetic component will help researchers and doctors to understand where individuals are on this spectrum, but arriving at this point will take more time and effort. For the moment, this study is an early but important step which refreshes the way we conceive of human circadian rhythms.

“Many people tend to consider their circadian rhythms as a single clock,” said forging. “What we show is that there is not really a clock, but there are two. One tries to follow Dawn and the other tries to follow the twilight, and they talk to each other.”

Kim, forging and their colleagues revealed that the circadian rhythms of the people were settled on the seasonality of sunlight by studying the sleep data of thousands of people using portable health devices, such as Fitbits. The participants were all resident doctors finishing a one -year internship who had registered in the study on the health of interns, funded by the National Institutes of Health.

Trainees are offbeat workers whose schedules change frequently, which means that their sleep hours too do it. In addition, these schedules are often in contradiction with the natural cycles of the day and the night.

The fact that the circadian rhythms of this population have shown seasonal dependence is a convincing argument for the way this characteristic is difficult in humans, which is not entirely surprising, the researchers said.

There is a lot of evidence of studies on fruit flies and rodents that animals have seasonal circadian clocks, said forging, and other researchers have thought that humans’ circadian clocks can behave in the same way. Now, the UM team has provided part of the strongest support to date to date to observe how this seasonality takes place in a great study of the real world.

“I think that in fact has a lot of meaning. The physiology of the brain has been at work for millions of years to try to follow dusk and dawn,” said forge. “Then industrialization is presented in the blink of an eye on the Evolution eye and, at the moment, we are still running to make up for their delay.”

Participants in the study on the health of interns also provide a saliva sample for DNA tests, which allowed the Kim team and forge to include a genetic component of their study. Genetic studies led by other researchers have identified a specific gene that plays an important role in the way the circadian clocks of other animals follow seasonal changes.

Humans share this gene, which allowed the UM team to identify a small percentage of trainees with slight variations in the genetic composition of this gene. For this group of people, the quarter work work was more disruptive for the alignment of their circadian clocks and their sleep hours during the seasons.

Again, this raises many questions in particular on the implications for health and the influence of quarter -work work on different people. But these are questions that researchers plan to explore in the future.

About this genetics and news of research in circadian rhythm

Author: Matt Davenport
Source: Michigan University
Contact: Matt Davenport – University of Michigan
Picture: The image is credited with Neuroscience News

Original search: Open access.
“”Of the seasonal moment and interindividual differences in the adaptation of the lag workBy Ruby Kim et al. NPJ Digital Medicine

Abstract

Of the seasonal moment and interindividual differences in the adaptation of the lag work

Millions of quarter workers in the United States are faced with an increased risk of depression, cancer and metabolic diseases, but individual responses to change work vary considerably.

We note that a preserved biological system of oscillators morning and evening, which has evolved for seasonal timing, can contribute to these interindividual differences.

In this study, we analyze the seasonality in the trainees of medical trainees, revealing that the variation of the summer admissions is in correlation with an increase in the circadian disalember after the quarter work.

Mathematical modeling suggests that the seasonal time influences the adaptation rate to new schedules, predicting the differential effects on the oscillators morning and evening.

In addition, we examine the genetic polymorphisms linked to seasonality in animals and note that human variants can have an impact on the speed with which circadian rhythms respond to planning changes.

On the basis of our results, we hypothesize that the vast interindividual differences in the adaptation of quarter work – critic for the health of quarter workers – can partly be explained by biological mechanisms for the moment.