Could daytime naps prevent brain shrinkage?

Although previous studies have shown that long naps could be an early warning sign of Alzheimer’s, more recent investigations suggested that having a short sleep during the day could improve people’s ability to learn.

Now researchers say they have found evidence to suggest that taking short naps is associated with larger brain volume and a reduced rate of brain shrinkage.

Brain shrinkage, a process that occurs with age, occurs faster in those with cognitive problems and neurodegenerative diseases, such as dementia and Parkinson’s.

In new research published in the journal Sleep Health, researchers from University College London and Uruguay’s Universidad de la República draw on data from the UK Biobank study, which collated genetic, health and lifestyle information from 500,000 participants aged 40-69.

The team used data from 35,080 Biobank participants to assess whether a combination of genetic factors – which had previously been associated with self-reported regular daytime naps – are also linked to aspects of brain health such as brain volume and cognition.

Given that such variants are set at birth, this approach enables researchers to examine napping’s impact on the brain, by reducing the importance placed on smoking, physical activity, and other lifestyle-related factors that can influence napping habits and brain health.

The researchers identified a link between a genetic predisposition to habitual daytime napping and a larger brain volume equivalent to between 2.6 and 6.5 fewer years of aging. This correlation could indicate that regular naps provide some protection against neurodegeneration through compensating for poor sleep.

Co-author Dr Victoria Garfield likened the study to a ‘natural randomised control trial’, noting that the variants being examined by the research team are quite common, being present in at least 1 per cent of the population.

‘Having a short daytime nap […] could help preserve brain volume and that’s a positive thing, potentially, [for] dementia prevention,’ said Dr Garfield, adding that previous research suggested a nap of up to 30 minutes could be beneficial.

However, Dr Garfield also noted that a plethora of other risk factors can lead to dementia and that many other factors can also affect brain volume.

Professor Tara Spire-Jones, president of the British Neuroscience Association, welcomed the study’s results while also noting its limitations – including that the study’s participants were all white British people, and that the participants’ self-reported sleep habits may not be entirely accurate.

‘This study is important because it adds to the data indicating sleep is important for brain health,” she said.

Related: The seven factors that could reduce dementia risk