Those nightcaps might affect your sleep more than you thought -- and not in a good way.

A new review of studies, published in the journal Alcoholism: Clinical & Experimental Research, shows that alcohol changes the normal rhythms of sleep by increasing the amount of time people spend in "deep sleep," but also decreasing the amount of time people spend in REM sleep by disrupting sleep during this stage, which is necessary for memory, concentration and motor skills.

"In sum, alcohol on the whole is not useful for improving a whole night's sleep," study researcher Chris Idzikowski, who is the director of the Edinburgh Sleep Centre, said in a statement. "Sleep may be deeper to start with, but then becomes disrupted. Additionally, that deeper sleep will probably promote snoring and poorer breathing. So, one shouldn't expect better sleep with alcohol."

Sleep has two parts that cycle back and forth: non-REM sleep, and REM sleep. The cycle takes 90 minutes, and continues on through the night -- it starts with non-REM sleep, and then goes on to REM sleep, and then back to non-REM sleep, and so on and so forth.

But alcohol increases the amount of time a person spends in the later stages of non-REM sleep, called "slow-wave sleep," or "deep sleep." While it may seem good that alcohol increases deep sleep -- which is important for the body to repair itself, as well as amp up the immune system -- it could actually have a negative effect among people who are predisposed to sleep apnea or sleep walking, by making them more vulnerable to these conditions.

"This effect on the first half of sleep may be partly the reason some people with insomnia use alcohol as a sleep aid," study researcher Irshaad Ebrahim, the medical director at the London Sleep Centre, said in a statement. "However, the effect of consolidating sleep in the first half of the night is offset by having more disrupted sleep in the second half of the night."

Researchers also found that alcohol seems to delay the onset of the first cycle of REM sleep, a consequence of which "would be less restful sleep," Idzikowski said in the statement.

In 2011, a study in the same journal also showed that alcohol could disrupt sleep, especially in women. That study, conducted by researchers at the University of Michigan, showed an association between alcohol consumption and sleepiness and disrupted sleep in women.

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  • Lullabies

    Soothing music before bedtime can really do the trick. A 2005 study found that older people who listened to 45 minutes of soft tunes before hitting the hay reported a <a href="http://www.blackwellpublishing.com/nursing/news/news.asp?id=124" target="_hplink">35 percent improvement in their sleep problems</a>. But it doesn't have to be Brahms, if that's not your style. As long as the music was soft and slow -- around 60 to 80 beats per minute -- it can spur <a href="http://news.bbc.co.uk/2/hi/health/4228707.stm" target="_hplink">physical changes known to promote sleep</a>, like a slower heart rate and breathing, the BBC reported. "We know that when a person closes their eyes they induce a certain frequency of brain waves," says Decker. Slow music may have a similar effect, he surmises, leading to sleep onset. <em>Flickr photo by <a href="http://www.flickr.com/photos/llimaorosa/112246369/" target="_hplink">Llima</a></em>

  • Warm Milk

    It was once thought that a glass of warm milk at bedtime would help send you off to dreamland because of the tryptophan, <em>The New York Times</em> reported, but milk and other protein-rich foods actually <a href="http://www.nytimes.com/2007/09/04/health/04real.html" target="_hplink">block tryptophan's sleepiness-inducing effects</a>. However, there might still be a psychological benefit to that warm milk, the <em>Times</em> concluded, calling it "as soothing as a favorite old blanket." "There have been some studies showing that when infants receive warm milk before bed, they'll dream a little bit more," says Decker, but the results don't hold true in adults. "It may be one of those myths that because it happens in children, adults think it may be true for them, too," he explains. However, many adults are actually at least slightly lactose intolerant, he says, meaning a warm mlik at bedtime may just lead to discomfort. <em>Flickr photo by <a href="http://www.flickr.com/photos/julianrod/152930252/" target="_hplink">julianrod</a></em>

  • Counting Sheep

    If your goal is to bore yourself to sleep, you might try counting sheep, or counting backwards by multiples of three or any of a number of other counting-related mind-numbers. But a 2002 study found that <a href="http://www.ncbi.nlm.nih.gov/pubmed/11863237" target="_hplink">imagining a more relaxing scene might be more effective</a>. The study observed 41 people with insomnia over a number of nights and asked them to try a variety of different sleep-inducing techniques, like counting sheep. On the nights they were told to imagine relaxing scenes like a beach, a massage or a walk in the woods, <a href="http://www.mentalfloss.com/blogs/archives/53137" target="_hplink">they fell asleep an average of 20 minutes sooner</a> than on the nights they were told to count sheep or were given no instructions, Mental Floss reported. Decker agrees. "Counting sheep in and of itself may not help," but can act as a ritual that prepares us for sleep, making it not unlike meditation. Counting sheep -- or more relaxing guided imagery -- helps us "focus on something other than life's stressors," he says. "Thinking about a soothing environment may be more restful than the way you spent the last eight hours!" <em>Flickr photo by <a href="http://www.flickr.com/photos/narciss/3716241331/" target="_hplink">Kr. B.</a></em>

  • Breathing Exercises

    Focusing on the breath, whether it's as part of a pre-bed yoga sequence or just a tuned-in awareness, can also have meditation-like effects in preparing for bed, says Decker, like lowering the heart rate. <em>Flickr photo by <a href="http://www.flickr.com/photos/perfectoinsecto/2363255713/" target="_hplink">Perfecto Insecto</a></em>

  • Warm Bath

    Your body temp <a href="http://www.health.com/health/condition-article/0,,20189095,00.html" target="_hplink">dips about two hours before bedtime</a>, <em>Health </em>magazine reported, a natural change that "triggers our brain for sleep onset", says Decker. Soaking in a warm bath beforehand boosts your temperature temporarily, but results in a dramatic, rapid cooldown after you get out that relaxes you and eases you into sleep. It's not necessarily the bath that lulls you to sleep, it's that resulting cooling of your body temperature, Decker emphasizes. Research shows that people who take a warm bath before bed not only <a href="http://www.ncbi.nlm.nih.gov/pubmed/2578367" target="_hplink">fall asleep more quickly</a>, but also report better quality of sleep, he says.

  • Alcohol

    Many people swear by a drink to unwind at the end of the day, but alcohol before bed can actually <a href="http://www.huffingtonpost.com/2012/07/04/fourth-of-july-sleep_n_1644627.html#slide=1176662" target="_hplink">disrupt your sleep</a>. You'll be more likely to wake up more often in the early-morning hours, wake up and not be to fall back to sleep or have disturbing dreams. "As alcohol is metabolized by the liver, it has a disruptive effect," says Decker. It takes a few hours to metabolize, he says, so a drink with dinner shouldn't be a problem, but anything too close to bedtime can be counterproductive. <em>Flickr photo by <a href="http://www.flickr.com/photos/rob-qld/2889139445/" target="_hplink">Rob Qld</a></em>

  • Get Out Of Bed

    It sounds crazy -- how will you ever get to sleep if you're not even in bed?! -- but it works, says Decker. "When a person stays in bed and they can't sleep, the bedroom can induce a certain level of anxiety," he says. "We say after 15 or 20 minutes, get out of bed, sit in another part of the house until you feel a little groggy, then go back to sleep," he says. "Staying in bed can condition you to become anxious in bed." A small 2011 study published in the <em>Archives of Internal Medicine</em> found that among the <a href="http://healthland.time.com/2011/01/27/cant-sleep-it-may-help-to-get-out-of-bed/" target="_hplink">adults studied who reported trouble sleeping</a>, those who spent <a href="http://www.thirdage.com/news/insomnia-cant-sleep-get-out-bed_1-26-2011 " target="_hplink">less time in bed had better sleeping habits</a>. <em>Flickr photo by <a href="http://www.flickr.com/photos/perfectoinsecto/3948115802/" target="_hplink">Perfecto Insecto</a></em>

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