If you want to sleep (and remember), cut the nightcap

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It's one of those long held myths. Having a nightcap, such as brandy or a little toddy of whisky with hot milk will help you unwind, and aid sleep.

Wrong.

Alcohol is definitely not good for sleep. It will make you feel sleepy initially and allow you to fall asleep quite quickly, but it causes you to end up having a poorer quality of sleep, waking more often and less feeling less refreshed.

And now there is an extra reason to skip the alcohol - it disrupts the important part of your sleep cycle that is essential for retaining memory.

Having a night on the tiles will, as is commonly known result in a sore head next morning often with sometimes little recollection of events from the night before. But even having just two drinks i.e. within the recommended safe levels of drinking will cut REM sleep as well as deep, slow wave sleep.

So that's one myth to dispatch. With many people regularly drinking most nights of the week believing they are doing no harm because they stick to the stipulated recommendations, the reality is that we are unwittingly not only impairing our sleep, but our ability to learn and retain information.

This is of particular concern in a society where regular binge drinking amongst the young, i.e teenagers and young adults is recognised to be a growing problem.

The other thing to consider here is in regards to older brains. Does age really change our sleep patterns and if so what impact does this have on our brains?

The short answer here is yes, ageing does appear to be associated with change in sleep patterns.

Doe this matter?

Again the short answer is yes because as with alcohol (which also disrupts slow wave sleep), it impacts on our ability to remember.

The importance of sleep and cognitive skills is only now really coming to be better understood.

As we age our sleep pattern starts to change. We may find it harder to fall asleep, or find we wake more frequently during the night. This has now been found to relate to declining memory function and loss of brain cells.

A study at UCLA recruited 33 healthy adults who were either younger (average age 20) of more mature (average age late 60's to 70's)

Each group were asked to memorise a list of word pairs. Ten minutes later they were asked to recall these and then left to sleep overnight while having an EEG recording taken of their brains. The following morning they were asked to recall the word pairs again while undergoing brain scans.

So what did the results show?

Well, perhaps not unexpectedly the older brains performed less well on the memory tests. What correlated along with this finding was that they also demonstrated a significant decrease in the amount of slow brain wave activity associated with deep sleep.

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Those with the worst sleep pattern disruption also had the worst memory performance. In addition these differences were associated with reduction of grey matter (i.e. brain cells) in the part of their frontal lobe called the medial prefrontal cortex.

This finding suggests that poor sleep, poor memory and brain deterioration are all interlinked.

Sleep is vital to the process of consolidation of memory. In slow wave sleep this is the time when it is thought that the transfer occurs of information from the hippocampus - the area of the brain associated with learning and memory, to other parts of the brain for long-term storage. In other words this is the process of embedding memory into our long-term memory storage banks. If this process is disrupted, we can't retain the information.

The role of the medial prefrontal cortex here is in regulating the amount of slow brain wave activity. If brain cells are lost from this area in association with the ageing process, not only is our sleep pattern altered as a result, but of course it impacts our ability to form long term memory.

What wasn't determined from this study (and a factor acknowledged by the researchers) was the fact that although the older cohort were all healthy and cognitively intact, so what wasn't known was the actual state of their brains from a neurodegenerative point of view. It could be that if they had early stages of dementia starting to develop this may have produced the effect on sleep patterns and memory as reported.

This is relevant to consider as sleep disturbance and memory loss are common features associated with Alzheimer's disease.

What would be useful here would be to see from future research whether improving sleep (especially slow brain wave sleep) can help to maintain memory and long-term memory formation and in addition ward off the clinical symptoms of Alzheimer's?

Now that would be worth knowing, to help us ensure we manage our sleep patterns better from an earlier age to retain our cognition for later.

Refs: 

Ebrahim, Irshaad O., Shapiro, Colin M., Williams, Adrian J. and  Fenwick, Peter B. (2013) Alcohol and Sleep I: Effects on Normal Sleep Journal of Alcoholism: Clinical and Experimental Research doi.org/10.1111/acer.12006 

Bryce A Mander, et al (2013) Prefrontal atrophy, disrupted NREM slow waves and impaired hippocampal-dependent memory in aging Nature Neuroscience  doi:10.1038/nn.3324

Image:

Bryce Mander Ageing brains show a weakening in brain waves associated with deep sleep (right)  compared with younger adults (left) with consequent memory impairments.