Page last updated: September 19, 2011
Heavy alcohol consumption can hinder the restorative function of sleep
Japanese researchers report that alcohol hinders the restorative functions of sleep. A study at the Akita University School of Medicine of the acute effects of alcohol on the relationship between sleep and heart rate variability (HRV) during sleep suggests that alcohol interferes with the restorative functions of sleep.
Researchers gave 10 healthy, male university students with a mean age of 21.6 years three different alcohol beverages at three week intervals: 0g (control), 0.5g (low dose), or 1.0g (high dose) of pure ethanol/kg of body weight. On the day of the experiment, a Holter electrocardiogram was attached to the subject for a 24-hour period; the subject was instructed to drink one of the three alcoholic beverages 100 minutes before going to bed; and polysomnography was then performed for eight hours. 
The study suggests that drinking leads to insomnia rather than quality sleep. As alcohol consumption increased, the heart rate increased and the spectral power of HRV measured at each frequency range decreased. Also, the low-frequency/high-frequency ratio that is considered an index of the balance between the sympathetic and parasympathetic systems was increased. This suggests that alcohol, in a dosage-dependent manner, suppresses the high-frequency component of HRV that is an indicator of parasympathetic nerve activity during sleep.
Source: Alcohol Has a Dose-Related Effect on Parasympathetic Nerve Activity During Sleep. Yohei Sagawaet al. Alcoholism: Clinical & Experimental Research.Article first published online: 16 Aug 2011.
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