Sleepy Head: Do people who take daytime naps have bigger brains?

Don't feel bad about taking your daily nap in the mid-afternoon. While earlier studies have suggested that protracted naps can be an early sign of Alzheimer's disease, more recent studies have shown that a quick nap can actually enhance learning.

According to a study conducted by scientists at UCL and the University of the Republic in Uruguay, taking naps during the day may delay the rate at which our brains shrink as we get older.

The researchers are hoping that by revealing the health advantages of daytime sleeping, the stigma surrounding it would be lessened.

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Benefits of short napping

“In line with these studies, we found an association between habitual daytime napping and larger total brain volume, which could suggest that napping regularly provides some protection against neurodegeneration through compensating for poor sleep,” the researchers note.

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According to the study, the average amount of brain volume between individuals who were programmed to nap frequently and those who did not was equal to 2.6 to 6.5 years of ageing. Therefore, experts advise that taking one 30-minute nap per day may help to decrease the shrinkage of the brain.

Senior author Dr Victoria Garfield, MRC Unit for Lifelong Health and Ageing at UCL, said as per The Independent, “Our findings suggest that, for some people, short daytime naps may be a part of the puzzle that could help preserve the health of the brain as we get older.”

In addition to the numerous risk factors for dementia, several additional factors can also have an impact on brain volume, according to Garfield.

According to Tara Spires-Jones, president of the British Neuroscience Association and deputy director of the Centre for Discovery Brain Sciences at the University of Edinburgh, who was not involved in the study, the research was "well-conducted," but it had limitations, including the fact that napping habits were self-reported.

The Guardian quoted her as telling the Science Media Centre that the findings "show a small but significant increase in brain volume in people who have a genetic signature associated with taking daytime naps." Despite these drawbacks, she argued that the study was intriguing because it "adds to the evidence indicating that sleep is important for brain health."

Scientists say further research is required to determine whether naps could aid in the prevention of illnesses like Alzheimer's.

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Methodology

Researchers used a method known as Mendelian randomisation to analyse DNA samples and brain scans from 35,080 participants in the UK Biobank study, a sizable biomedical database and research resource that monitored UK citizens from 2006 to 2010. The study was published on Monday in the journal Sleep Health.

Mendelian randomisation is a statistical method that makes use of genetics to shed light on the connection between an exposure and a result.

The researchers investigated whether a set of genetic variations previously linked to self-reported frequent daily naps were also connected to brain volume, cognition, and other characteristics of brain health.

“By looking at genes set at birth, Mendelian randomisation avoids confounding factors occurring throughout life that may influence associations between napping and health outcomes,” said lead author Valentina Paz, a researcher at the University of the Republic of Uruguay and UCL in the statement.

The method enables researchers to probe the impact of napping on the brain by reducing the impact of lifestyle factors that can affect people's napping habits and brain health, such as smoking or physical activity since such variants are set at birth and are assumed to be randomly assigned.

“It is like a natural randomised control trial,” said Dr Victoria Garfield, a co-author of the study from University College London, adding that the variants were quite common. “They’re present in around at least one per cent of the population, which is actually quite a lot of people.”

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Too much napping can be harmful

An early stage of dementia in older persons may be indicated by frequent naps or regular naps that last for long amounts of time during the day, according to earlier research.

According to a study published in Alzheimer's and Dementia: The Journal of the Alzheimer's Association in March last year, elderly people who napped more than an hour per day or at least once a day were 40% more likely to develop Alzheimer's than those who did not nap daily or napped for less than an hour per day.

People who frequently snooze have a higher risk of getting high blood pressure and suffering a stroke, CNN cited a study published in July 2022.

Compared to study participants who never napped, those who frequently napped throughout the day had a 24 per cent increased risk of having a stroke and a 13 per cent increased risk of developing high blood pressure over time.

Dr Raj Dasgupta, an associate professor of clinical medicine at the Keck School of Medicine at the University of Southern California and a sleep specialist, previously told CNN that excessive napping could be a sign of an underlying sleep issue. “Sleep disorders are linked to an increase in stress and weight regulation hormones which can lead to obesity, high blood pressure, type 2 diabetes – all risk factors for heart disease,” he said. “I do believe napping is a warning sign of an underlying sleep disorder in certain individuals.”

With inputs from agencies

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