Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Body's clock may lead to increased risk for fainting during the nighttime

08.03.2011
Fainting, or syncope, is quite common. About 50% of people will experience fainting at some point during their lifetime.

The most common type of fainting is vasovagal syncope (VVS) that is caused by a sudden drop in blood pressure resulting in reduced blood flow to the brain. VVS can occur in healthy people due to inappropriate cardiovascular responses to certain behavioral or emotional triggers such as fear, needle prick or even standing up. VVS has a daily pattern with more occurrences during the morning. This daily pattern is possibly due to the daily distribution of behavioral and emotional stimuli or perhaps due to influences from the internal circadian system, or 'body clock'. In a new study, researchers at Brigham and Women's Hospital (BWH) provide strong evidence that the circadian system may contribute to the daily pattern of VVS via its influences on physiological responses to changes in body posture. These findings are published on March 8, 2011 in the journal Circulation.

Lead study author Kun Hu, PhD, of the Division of Sleep Medicine at BWH said that "the susceptibility to VVS is probably present in all healthy humans. Fainting can cause an individual to fall which can result in severe trauma, including skull and limb bone fractures. Recurrent VVS can also affect quality of life due to reduced activities and social adjustment. Understanding the causes of VVS is important for diagnosis, prevention and treatment of people with a history of recurrent VVS".

In this study, repeated tilt-table tests were used to determine the susceptibility to VVS across the day and night in twelve healthy participants who stayed in a controlled laboratory environment for almost 2 weeks. To measure the influence of the internal body clock on VVS while controlling for other factors including the sleep/wake cycle, meals and the environment, the researchers scheduled all behaviors of participants while they lived on a recurring 20-hour "day" (with 6.7 hours scheduled for sleep and 13.3 hours for wake). The study was performed in dim light so that the internal body clock still oscillated with an approximate 24-hour period. Core body temperature was measured throughout to indicate the times of the internal body clock. To stop the participants from actually fainting, signs of imminent VVS (presyncope) were closely monitored and tilt-table tests were immediately aborted whenever there were notable symptoms of nausea, dry mouth, dizziness, or low blood pressure or rapidly falling blood pressure.

The researchers found that the vulnerability to presyncope has a strong connection to the internal body clock, with susceptibility nine times higher at the circadian times between 10:30 PM and 10:30 AM compared to between 10:30 AM through 10:30 PM. The highest risk for presyncope occurred at the circadian time corresponding to 4:30 AM. "This vulnerable period may have relevance to individuals who remain awake or wake up frequently during the night, such as shift workers, parents feeding their infants and elderly people with increased nocturia or insomnia. These people may be at higher risk for syncope due to their postural changes during the night" said one of the investigators, Dr. Steven Shea of the Division of Sleep Medicine at BWH.

In addition, this study highlights the importance of performing tilt-table tests at similar circadian times when comparing responses of different individuals or the same person before and after treatments for syncope. The results also suggest that a higher sensitivity may be achieved by performing tilt-table testing during early morning hours or the night.

The research was funded by grants from the National Institutes of Health and the Harvard Catalyst.

Brigham and Women's Hospital (BWH) is a 793-bed nonprofit teaching affiliate of Harvard Medical School and a founding member of Partners HealthCare, an integrated health care delivery network. BWH is the home of the Carl J. and Ruth Shapiro Cardiovascular Center, the most advanced center of its kind. BWH is committed to excellence in patient care with expertise in virtually every specialty of medicine and surgery. The BWH medical preeminence dates back to 1832, and today that rich history in clinical care is coupled with its national leadership in quality improvement and patient safety initiatives and its dedication to educating and training the next generation of health care professionals. Through investigation and discovery conducted at its Biomedical Research Institute (BRI), BWH is an international leader in basic, clinical and translational research on human diseases, involving more than 900 physician-investigators and renowned biomedical scientists and faculty supported by more than $ 537 M in funding. BWH is also home to major landmark epidemiologic population studies, including the Nurses' and Physicians' Health Studies and the Women's Health Initiative. For more information about BWH, please visit www.brighamandwomens.org.

Holly Brown-Ayers | EurekAlert!
Further information:
http://www.brighamandwomens.org

More articles from Life Sciences:

nachricht Embryonic development: How do limbs develop from cells?
18.05.2018 | Humboldt-Universität zu Berlin

nachricht Reading histone modifications, an oncoprotein is modified in return
18.05.2018 | American Society for Biochemistry and Molecular Biology

All articles from Life Sciences >>>

The most recent press releases about innovation >>>

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

Im Focus: Explanation for puzzling quantum oscillations has been found

So-called quantum many-body scars allow quantum systems to stay out of equilibrium much longer, explaining experiment | Study published in Nature Physics

Recently, researchers from Harvard and MIT succeeded in trapping a record 53 atoms and individually controlling their quantum state, realizing what is called a...

Im Focus: Dozens of binaries from Milky Way's globular clusters could be detectable by LISA

Next-generation gravitational wave detector in space will complement LIGO on Earth

The historic first detection of gravitational waves from colliding black holes far outside our galaxy opened a new window to understanding the universe. A...

Im Focus: Entangled atoms shine in unison

A team led by Austrian experimental physicist Rainer Blatt has succeeded in characterizing the quantum entanglement of two spatially separated atoms by observing their light emission. This fundamental demonstration could lead to the development of highly sensitive optical gradiometers for the precise measurement of the gravitational field or the earth's magnetic field.

The age of quantum technology has long been heralded. Decades of research into the quantum world have led to the development of methods that make it possible...

Im Focus: Computer-Designed Customized Regenerative Heart Valves

Cardiovascular tissue engineering aims to treat heart disease with prostheses that grow and regenerate. Now, researchers from the University of Zurich, the Technical University Eindhoven and the Charité Berlin have successfully implanted regenerative heart valves, designed with the aid of computer simulations, into sheep for the first time.

Producing living tissue or organs based on human cells is one of the main research fields in regenerative medicine. Tissue engineering, which involves growing...

Im Focus: Light-induced superconductivity under high pressure

A team of scientists of the Max Planck Institute for the Structure and Dynamics of Matter (MPSD) at the Center for Free-Electron Laser Science in Hamburg investigated optically-induced superconductivity in the alkali-doped fulleride K3C60under high external pressures. This study allowed, on one hand, to uniquely assess the nature of the transient state as a superconducting phase. In addition, it unveiled the possibility to induce superconductivity in K3C60 at temperatures far above the -170 degrees Celsius hypothesized previously, and rather all the way to room temperature. The paper by Cantaluppi et al has been published in Nature Physics.

Unlike ordinary metals, superconductors have the unique capability of transporting electrical currents without any loss. Nowadays, their technological...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

VideoLinks
Industry & Economy
Event News

Save the date: Forum European Neuroscience – 07-11 July 2018 in Berlin, Germany

02.05.2018 | Event News

Invitation to the upcoming "Current Topics in Bioinformatics: Big Data in Genomics and Medicine"

13.04.2018 | Event News

Unique scope of UV LED technologies and applications presented in Berlin: ICULTA-2018

12.04.2018 | Event News

 
Latest News

Supersonic waves may help electronics beat the heat

18.05.2018 | Power and Electrical Engineering

Keeping a Close Eye on Ice Loss

18.05.2018 | Information Technology

CrowdWater: An App for Flood Research

18.05.2018 | Information Technology

VideoLinks
Science & Research
Overview of more VideoLinks >>>