Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Human circadian clocks couple to local sun time

24.01.2007
By assessing the daily activity patterns of thousands of individuals living in different geographical locations, researchers have found evidence that the human circadian clock becomes coupled to so-called local sun time despite the fact that people live and work according to a common "social time" that is determined by time zones.

The work also indicated that city dwellers appear to experience a relatively decreased influence of local sun time relative to those living in more sparsely populated areas.

The findings appear in the January 23rd issue of Current Biology and are reported by Till Roenneberg of Ludwig-Maximilians-Universität, Germany; C. Jairaj Kumar, of Kasturba Medical College, India; and Martha Merrow, of the University of Groningen, in The Netherlands.

Because our watches and clocks are set according to time zones, which are constant over multiple longitudes, rather than according to local sun time, which continuously changes across longitudes, there is often a discrepancy between the natural-light cues one receives as a result of local sun time and the "social" cues one receives as a result of clock time. The extent of such discrepancies depends on the time of year and one's location within a time zone, but can be substantial: In some cities, midnight (according to clock time) can fall well beyond an hour away from "mid-dark." The relative influences of these two types of cues on circadian rhythms are not fully understood by scientists, and in the new work, researchers sought to address this issue by comparing the circadian behaviors of people experiencing these influences to different extents in their daily lives.

... more about:
»Influence »Zone »chronotype »circadian

The measure used to assess patterns of daily activity is the so-called chronotype, which is determined by answers to questionnaires that assess patterns of habitual activity and rest during work days and free time.

In the present study, the authors compared the chronotypes of over 21,000 individuals living in different geographical locations across Germany. Individuals were compared according to the town size in which they lived: The first group included those in areas with a population size of 300,000 or less, while other groups corresponded to individuals living in towns and cities of larger sizes.

The researchers found that within the first group--individuals in more lightly populated regions--chronotypes were tightly coupled to sun time, while within groups corresponding to more densely populated towns and cities, chronotypes showed a progressively weaker coupling to sun time.

City dwelling potentially impacts the influence of sunlight as a zeitgeber because urban dwellers are typically exposed to less natural light than individuals inhabiting less densely populated areas. The authors propose that the gradual uncoupling of the circadian clock of city dwellers from local sun time may reflect the relative strength of natural-light and social cues in influencing activity patterns. When natural-light cues are more abundant--as seems to be the case in more sparsely populated areas--human circadian rhythm entrains to local sun time.

Past work has indicated that as influences on the circadian clock--known as "zeitgebers"--become weaker, chronotypes tend to become later--that is, daily activity is shifted later in the day. And indeed, the present study found that chronotypes became later with increasing population size.

Erin Doonan | EurekAlert!
Further information:
http://www.current-biology.com

Further reports about: Influence Zone chronotype circadian

More articles from Life Sciences:

nachricht Nanoparticle Exposure Can Awaken Dormant Viruses in the Lungs
16.01.2017 | Helmholtz Zentrum München - Deutsches Forschungszentrum für Gesundheit und Umwelt

nachricht Cholera bacteria infect more effectively with a simple twist of shape
13.01.2017 | Princeton University

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Designing Architecture with Solar Building Envelopes

Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.

As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...

Im Focus: How to inflate a hardened concrete shell with a weight of 80 t

At TU Wien, an alternative for resource intensive formwork for the construction of concrete domes was developed. It is now used in a test dome for the Austrian Federal Railways Infrastructure (ÖBB Infrastruktur).

Concrete shells are efficient structures, but not very resource efficient. The formwork for the construction of concrete domes alone requires a high amount of...

Im Focus: Bacterial Pac Man molecule snaps at sugar

Many pathogens use certain sugar compounds from their host to help conceal themselves against the immune system. Scientists at the University of Bonn have now, in cooperation with researchers at the University of York in the United Kingdom, analyzed the dynamics of a bacterial molecule that is involved in this process. They demonstrate that the protein grabs onto the sugar molecule with a Pac Man-like chewing motion and holds it until it can be used. Their results could help design therapeutics that could make the protein poorer at grabbing and holding and hence compromise the pathogen in the host. The study has now been published in “Biophysical Journal”.

The cells of the mouth, nose and intestinal mucosa produce large quantities of a chemical called sialic acid. Many bacteria possess a special transport system...

Im Focus: Newly proposed reference datasets improve weather satellite data quality

UMD, NOAA collaboration demonstrates suitability of in-orbit datasets for weather satellite calibration

"Traffic and weather, together on the hour!" blasts your local radio station, while your smartphone knows the weather halfway across the world. A network of...

Im Focus: Repairing defects in fiber-reinforced plastics more efficiently

Fiber-reinforced plastics (FRP) are frequently used in the aeronautic and automobile industry. However, the repair of workpieces made of these composite materials is often less profitable than exchanging the part. In order to increase the lifetime of FRP parts and to make them more eco-efficient, the Laser Zentrum Hannover e.V. (LZH) and the Apodius GmbH want to combine a new measuring device for fiber layer orientation with an innovative laser-based repair process.

Defects in FRP pieces may be production or operation-related. Whether or not repair is cost-effective depends on the geometry of the defective area, the tools...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

12V, 48V, high-voltage – trends in E/E automotive architecture

10.01.2017 | Event News

2nd Conference on Non-Textual Information on 10 and 11 May 2017 in Hannover

09.01.2017 | Event News

Nothing will happen without batteries making it happen!

05.01.2017 | Event News

 
Latest News

Multiregional brain on a chip

16.01.2017 | Power and Electrical Engineering

New technology enables 5-D imaging in live animals, humans

16.01.2017 | Information Technology

Researchers develop environmentally friendly soy air filter

16.01.2017 | Power and Electrical Engineering

VideoLinks
B2B-VideoLinks
More VideoLinks >>>