Published in:
01-01-2009 | Original Article
Effects of low ambient temperature on heart rate variability during sleep in humans
Authors:
Kazue Okamoto-Mizuno, Kazuyo Tsuzuki, Koh Mizuno, Yasushi Ohshiro
Published in:
European Journal of Applied Physiology
|
Issue 2/2009
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Abstract
The effects of cold exposure on heart rate variability (HRV) during sleep were examined. Eight male subjects slept under three different conditions: 3°C, 50–80% relative humidity (RH) [3]; 10°C, 50% RH [10]; and 17°C 50% RH [17]. No significant differences were observed in HRV during rapid eye movement sleep (REM) and wakefulness. The ratio of the low frequency (LF) to high frequency component (HF) of HRV (LF/HF) significantly differed among the conditions during stage 2 and slow wave sleep (SWS) that decreased as the ambient temperature decreased. The normalized LF [LF/(LF + HF)] significantly decreased in 3 and 10 than in 17 during SWS. In low ambient temperature, predominant cardiac parasympathetic activity during stage 2 with no significant difference during REM and wakefulness may cause variations in HRV at transition from stage 2 to REM and wakefulness. These results may partly explain the peak in adverse cardiac events during winter.