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Researchers in Israel may have discovered why myocardial infarction and other cardiac events occur more frequently during early morning hours.
Using a new, noninvasive finger probe, researchers at Technion–Israel Institute of Technology in Haifa evaluated peripheral blood flow overnight in 17 adults with mild-to-moderate sleep apnea and in nine healthy controls. In both groups they found that peripheral arteries were most constricted during rapid eye movement (REM) sleep.Along with the intense brain activity and eye movements of REM sleep, the researchers said activation of the sympathetic branch of the autonomic nervous system during REM sleep increases heart rate and blood pressure. "In these studies, we saw robust changes in vasoconstriction and resistance to blood flow during REM sleep. Such marked changes strongly suggest an association between REM sleep and increased cardiac events," said Peretz Lavie, PhD, head of the Technion Sleep Laboratory.
Voelker R. Blood Flow During REM. JAMA. 2000;284(2):169. doi:10.1001/jama.284.2.169-JWM00005-3-1