Getting enough sleep is linked to better cognitive function, memory and mood, among other benefits. Photo: ERIC AUDRAS
By Velvet Winter for the ABC
Naps. They have the potential to soothe anything from an overwhelmed toddler to a raging hangover.
But a new study suggests they could also be the key to retaining brain volume as we age.
Researchers at University College London and the University of the Republic in Uruguay, analysed data from 35,080 UK Biobank participants to find out if a combination of genetic variants that have been associated with self-confessed daytime nappers are also linked to brain volume and cognition.
Ultimately, the team concluded that there's an association between genetic predispositions to habitual daytime napping and larger brain volume equivalent to 2.6 to 6.5 fewer years of ageing.
However, University of Queensland Professor of Sleep and Health Simon Smith says the results of the study do not necessarily mean that regular naps will lead you to the fountain of youth.
"Brain shrinkage or 'atrophy' can occur in specific health conditions, such as excessive alcohol use, stroke, Alzheimer's. It can also occur as part of normal ageing, but any changes can be quite subtle," he told ABC News.
"This study didn't actually look at shrinkage, but just at relative brain sizes between adults aged 40-69. More than half of the participants never or rarely napped."
Why do humans nap?
It might seem obvious but if you feel compelled to nap it means that your body needs that time to rest and recuperate.
"Daytime napping is very common in young children, and this is likely to reflect the importance of sleep for new learning, growth, and resilience," Professor Smith says.
"In children, naps have been shown to improve new learning, although this depends on the age of the child."
While humans tend to stop regular naps by the time schooling starts, Professor Smith says napping remains fairly common throughout the life span in response to illness, lack of sleep, and in response to jet-lag or a change in routines.
"In adults, naps are more often taken when very tired, and can result in improvements in cognition because of a reduction in tiredness. The effects of regular napping are less certain."
In children, naps have been shown to improve new learning. Photo: 123rf.com
How long should we nap for?
Professor Smith says the most sure-fire way to make sure that your nap leaves you refreshed is to keep your sleep on the shorter side.
"There has been a lot of research on nap duration. Around 15-20 minutes is often recommended," he says
"This allows enough time to really get to sleep, but not so long as to cause 'sleep inertia' or the grogginess you can feel after waking up."
Is it beneficial to substitute night-time sleep for day-time sleep?
Probably not.
"Generally, night-time sleep is best, and international guidelines around recommended hours of sleep are based on night-time sleep duration," Professor Smith says.
"Our internal body clocks also work to keep sleep within the night time hours.
"Napping isn't necessarily a bad thing but may reduce some of the need or 'drive' for night-time sleep."
So, should we all be scheduling an afternoon siesta to keep our brains healthy?
Rest assured for nervous nappers, skipping a sleep in the daytime is probably not going to cause your brain to age faster.
Social jetlag, sleep chronotypes and why we should be embracing the shut-eye we get
According to sleep experts, being in social jetlag for a prolonged period could have adverse effects on your health.
"This study found a modest relationship between daytime napping and brain size, based on scans. It isn't clear whether naps increase brain size or vice versa," Professor Smith says.
"It also didn't find important relationships between daytime napping and cognitive outcomes, and didn't look at other important outcomes such as physical health or wellbeing.
"It is much to early to base recommendations for napping based on those results."
Professor Smith says that while you don't necessarily have to be militant with your napping habits, if you feel the urge to sleep and you're in an environment that allows it, you should definitely do so.
"Naps can be more common among older adults, and may be a way to catch up on sleep, or may be opportunistic - that is, if you want to nap during the early afternoon drowsy period, why not.
"This is generally regarded as OK, as long as it doesn't cause problems with night-time sleep."
While the study might not be an iron clad excuse to pencil in some day time shut eye, Professor Smith says it opens the door for more research.
"The question of the role of daytime sleep (napping) and night-time sleep and longer-term cognitive functions is really important.
"It matters for how we think about children's napping in early care and primary school, for workers - especially shift workers or anyone working irregular hours - and for older adults facing the prospect of cognitive decline.
"Well-designed studies that look at a broader range of important outcomes, and over a longer time period, will help answer those questions.
"We know how to improve sleep for many people, so if we can help brain function in later life that way then we should."
* This story was first published on the ABC.
