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"Body's Clock May Increase Risk For Fainting During the Nighttime"

March 7, 2011

An article in the March issue of Circulation reveals new findings suggesting that vulnerability to fainting (or vasovagal syncope, VVS) is related to circadian rhythm. The study, entitled "Endogenous circadian rhythm in vasovagal response to head-up tilt" revealed that the risk of fainting is nine times higher at the circadian times between 10:30pm and 10:30am compared to between 10:30am through 10:30pm. The highest risk occurred at the circadian time corresponding to 4:30am.

Lead study author Kun Hu, PhD, of the Division of Sleep Medicine 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”. 

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