Pre-Bed Booze May Bust Rest

A nightcap may force the body to work harder at repair during sleep, making for a less restful night. Katherine Harmon reports

August 16, 2011, SciAm M&B

People often turn to wine, beer or cocktails to unwind at the end of the day. These drinks might seem to be relaxing and to aid sleep. But research has shown that people who drink alcohol in the evenings actually get less REM sleep and have less restful nights.

Now a study demonstrates that late-night alcohol might decrease the amount of necessary overnight repair work that the body can do.

Subjects in the study drank strong, weak or alcohol-free beverages an hour-and-40-minutes before going to bed. The more booze the volunteers imbibed, the higher their overnight heart rate. These rapid beats were an indication that their bodies were not in the most productive rest mode, say the researchers. The work appears in the journal Alcoholism: Clinical & Experimental Research. [Yohei Sagawa et al., "Alcohol Has a Dose-Related Effect on Parasympathetic Nerve Activity During Sleep"]

The findings might help explain why those who frequently drink often suffer from insomnia at night and sleepiness during the day, as well as more long-term health effects.

So if you're looking for better, more healthful sleep, maybe avoid the night-time nightcap.
—Katherine Harmon


For those interested, here is the study abstract:


Alcohol Has a Dose-Related Effect on Parasympathetic Nerve Activity During Sleep

• Yohei Sagawa,
• Hideaki Kondo,
• Namiko Matsubuchi,
• Takaubu Takemura,
• Hironobu Kanayama,
• Yoshihiko Kaneko,
• Takashi Kanbayashi,
• Yasuo Hishikawa,
• Tetsuo Shimizu

Article first published online: 16 AUG 2011

Keywords:

• Alcohol;
• Ethanol;
• Sleep;
• Autonomic Nerve Activity;
• Heart Rate Variability

Background: The aim of this study was to identify the acute effects of ethanol on the relationship between sleep and heart rate variability (HRV) during sleep.
Methods: Ten healthy male university students were enrolled in this study. An alcoholic beverage was given to each subject at a dosage of 0 (control), 0.5 (low dose: LD), or 1.0 g (high dose: HD) of pure ethanol/kg of body weight. All experiments were performed at 3-week intervals. On the day of the experiment, a Holter electrocardiogram was attached to the subject for a 24-hour period, and the subject was instructed to drink the above-described dosage of alcoholic beverage 100 minutes before going to bed; polysomnography was then performed for 8 hours. Power spectral analysis of the HRV was performed using the maximum entropy method, and the low- (LF: 0.04 to 0.15 Hz) and high-frequency (HF: 0.15 to 0.4 Hz) components along with LF/HF ratio were calculated.
Results: As alcohol consumption increased, the heart rate increased and the spectral power of HRV measured at each frequency range decreased. Higher doses of ethanol also increased the LF/HF ratio compared with the measured ratio of the control group.
Conclusions: Acute ethanol intake inhibits parasympathetic nerve activity and results in predominance of sympathetic nerve activity during sleep, in a dosage-dependent manner. The results of this study suggest that ethanol interferes with the restorative functions of sleep