“It’s generally believed that having a nightcap may aid sleep, especially getting to sleep” says Seiji Nishino, Director of the Sleep & Circadian Neurobiology Lab at Stanford University School of Medicine. “This may be true for some people who have small amounts of alcohol intake. However, it should be noted that large amounts of alcohol intake interfere with sleep quality and the restorative role of sleep.”
This was no surprise – For a long time researchers have known that large amounts of alcohol shortens the length of time that it takes you to make that transition from full wakefulness to sleep (or Sleep Latency); increases your slow-wave sleep (SWS) and suppresses rapid eye movement (REM) during the first half of your sleep. During the second half of sleep, REM increases and sleep becomes shallower.
How do they know what happens? A study just released that was done on the acute effects of alcohol and the relationship between sleep and heart rate variability (HRV) during sleep, has shown that alcohol interferes with the restorative functions of sleep. Alcohol directly affects overall sleep architecture,” said Yohei Sagawa, a physician in the Department of Neuropsychiatry at the Akita University School of Medicine.
For this study, they gave 10 healthy, male university students with (average age of 21.6), 3 different alcohol beverages at 3 week intervals: 0g (control), 0.5g (low dose) or 1.0g (high dose). On the day of the experiment, a holter electrocardiogram was attached for a 24-hour period; the student was instructed to drink one of the 3 alcoholic beverages 100 minutes before going to bed; and polysomnography was then performed for 8 hours while they slept. The researchers were focused on the relationship between the students’ heart rate variability and their sleep.
The team found that alcohol increased heart rate and interfered with the restorative functions of sleep — and the more alcohol the participants drank, the greater the effect. “Although the first half of sleep after alcohol intake looks good on the EEG, the result of the assessment regarding the autonomic nervous system shows that drinking leads to insomnia rather than good sleep.”
The effect on habitual drinkers might be even worse, a study co-author said. “This study evaluated the effects on sleep after only a single dose of alcohol and easily found negative health consequences,” Seiji Nishino, said in an August 2011 news release. “Many people habitually drink alcohol and if the reduction of healthy parasympathetic nervous system activity during sleep occurs routinely as the result of drinking, the negative health consequences may be much larger and could bring about various diseases.” It is reported that habitual drinkers with high blood pressure are often associated with reductions of parasympathetic nerve activities.”
Sagawa agreed. “Many alcoholics and habitual drinkers suffer from insomnia” and it’s been shown that “suppressed parasympathetic nerve activity is the result of alcohol drinking. Thus, it is concluded that suppressed parasympathetic nerve activity is associated with insomnia, which includes difficulty getting to sleep, early-morning awakening, lack of a sense of deep sleep and difficulty maintaining sleep.”
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Jeanne Ricks, CHC, AADP