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A glass of alcohol before bedtime may get you off to sleep faster but it can disrupt your night’s slumber, say researchers who have reviewed the evidence.

The London Sleep Centre team says studies show alcohol upsets our normal sleep cycles.

While it cuts the time it takes to first nod off and sends us into a deep sleep, it also robs us of one of our most satisfying types of sleep, where dreams occur.

Used too often, it can cause insomnia.

Many advocate a nightcap – nursing homes and hospital wards have even been known to serve alcohol – but Dr. Irshaad Ebrahim and his team advise against it.

Dr. Irshaad Ebrahim, medical director at the London Sleep Centre and co-author of the latest review, published in the journal Alcoholism: Clinical & Experimental Research, said: “We should be very cautious about drinking on a regular basis.

“One or two glasses might be nice in the short term, but if you continue to use a tipple before bedtime it can cause significant problems.

“If you do have a drink, it’s best to leave an hour and a half to two hours before going to bed so the alcohol is already wearing off.”

A glass of alcohol before bedtime may get you off to sleep faster but it can disrupt your night's slumber

A glass of alcohol before bedtime may get you off to sleep faster but it can disrupt your night’s slumber

He said people could become dependent on alcohol for sleep.

And it could make sleep less restful and turn people into snorers.

“With increasing doses, alcohol suppresses our breathing. It can turn non-snorers into snorers and snorers into people with sleep apnoea – where the breathing’s interrupted.”

From the hundred or more studies that Dr. Irshaad Ebrahim’s team looked at, they analyzed 20 in detail and found alcohol appeared to change sleep in three ways.

Firstly, it accelerates sleep onset, meaning we drop off faster.

Next, it sends us into a very deep sleep.

These two changes – which are identical to those seen in people who take antidepressant medication – may be appealing and may explain why some people with insomnia use alcohol.

But the third change – fragmented sleep patterns the second half of the night – is less pleasant.

Alcohol reduces how much time we spend in rapid eye movement (REM) sleep – the stage of sleep where dreams generally occur.

As a consequence, the sleep may feel less restful, said Dr. Irshaad Ebrahim.

Chris Idzikowski, director of the Edinburgh Sleep Centre, said: “Alcohol on the whole is not useful for improving a whole night’s sleep. 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.”

The Sleep Council said: “Don’t over-indulge. Too much food or alcohol, especially late at night, just before bedtime, can play havoc with sleep patterns.

“Alcohol may help you fall asleep initially, but will interrupt your sleep later on in the night. Plus you may wake dehydrated and needing the loo.”

Scientists have discovered that male fruit flies that have been rejected by females drink significantly more alcohol than those that have mated freely.

Published in Science, the study suggests that alcohol stimulates the flies’ brains as a “reward” in a similar way to sexual conquest.

The work points to a brain chemical called neuropeptide F, which seems to be regulated by the flies’ behavior.

Human brains have a similar chemical, which may react in a similar way.

The connection between alcohol and this chemical, which in humans is known as neuropeptide Y, has already been noted in studies involving hard-drinking mice.

The new work explores the link between such reward-seeking and the study of social interactions, said the lead author of the report Galit Shohat-Ophir, now of the Howard Hughes Medical Institute in Virginia, US.

“It is thought that reward systems evolved to reinforce behaviors that are important for the survival of both individuals and species, like food consumption and mating,” said Dr. Galit Shohat-Ophir.

“Drugs of abuse kind of hijack the same neural pathways used by natural rewards, so we wanted to use alcohol – which is an extreme example of a compound that can affect the reward system – to get into the mechanism of what makes social interaction rewarding for animals.”

Working in the laboratory of Ulrike Heberlein at the University of California, San Francisco, Dr. Galit Shohat-Ophir and colleagues subjected a number of flies to a wide variety of fates.

In one set of experiments, male flies were put in a box with five virgin females, which were receptive to the males’ advances. In another, males were locked up with females that had already mated and which thus roundly rejected the males’ attempts at sex.

Offered either their normal food slurry or a version charged with 15% alcohol, the mated males avoided the alcohol, whereas the sexually deprived males went on a comparative bender.

The team then went on a hunt for a chemical that could tie the two parts of this story together, hitting on neuropeptide F (NPF).

Scientists have discovered that male fruit flies that have been rejected by females drink significantly more alcohol than those that have mated freely

Scientists have discovered that male fruit flies that have been rejected by females drink significantly more alcohol than those that have mated freely

They found that the heavy-drinking rejected males had a lowered level of the chemical, and sated, mated males had an elevated level.

“What we think is that these NPF levels are some kind of <<molecular signature>> to the experience,” Dr. Galit Shohat-Ophir explained.

To show that the NPF is actually responsible for the change rather than just associated with it, the researchers actively manipulated just how much NPF was in the flies’ brains.

Those with depressed levels acted like the rejected males, and those with elevated levels behaved like the mated males.

“What this leads us to think is that the fly brain – and presumably also other animals’ and human brains – have some kind of a system to control their level of internal reward, that once the internal reward level is down-regulated it will be followed by behavior that will restore it back,” Dr. Galit Shohat-Ophir said.

It is tempting, given that humans share a similar brain chemical, to imagine that NPF drives human behavior as well.

However, in an accompanying article in Science, Troy Zars of the University of Missouri wrote that “anthropomorphizing the results from flies is difficult to suppress, but the relevance to human behavior is obviously not yet established”.

Nevertheless, he suggested, “links a rewarding social interaction with a lasting change in behavior”.

“Identifying the NPF system as critical in this linkage offers exciting prospects for determining the molecular and genetic mechanisms of reward and could potentially influence our understanding of the mechanisms of drugs of abuse.”