Your Afternoon Nap Might Not Be Laziness
A 2023 study of nearly 379,000 people found something surprising about napping and brain health. Here is what the research actually says and what it does not.
Most people feel guilty about napping. They call it lazy. They call it unproductive. They wake up almost apologizing for needing rest.
But a 2023 study published in Sleep Health made me look at naps differently, not because it proved naps prevent dementia, but because it found something more subtle, and honestly, more interesting.
People genetically predisposed to habitual daytime napping had larger total brain volume.
And in brain aging research, that matters.
So let us talk about what the study actually found. And just as importantly, what it did not find.
The Study — What They Did
Researchers from University College London and the University of the Republic in Uruguay looked at nearly 379,000 participants from the UK Biobank.
The question was simple: Is habitual daytime napping associated with better brain health?
But the more important question was this: Could that relationship actually be causal?
Because most sleep research is observational. It can show that two things are linked, but it cannot always tell us what is causing what. If people who nap have different brain health, is the nap helping? Or are people with different health patterns simply more likely to nap?
That distinction matters enormously.
So the researchers used a method called Mendelian randomization which uses genetic variants linked to daytime napping to help estimate whether napping itself may be causally related to brain outcomes. It is not the same as randomly assigning people to nap every day for years. But it is meaningfully stronger than a simple observational survey. And what they found was worth paying attention to.
The Main Finding
People with genetic variants linked to habitual daytime napping had an estimated larger total brain volume.
That may sound small. But in brain aging research, it is not nothing.
Brain volume naturally declines with age. After 40, this process gradually accelerates. Less brain volume is associated with higher risk of dementia and cognitive decline. So when researchers find a measurable, causally-linked difference in total brain volume, it is worth taking seriously.
Now, this does not mean a nap prevents dementia. It does not mean a nap reverses brain aging. But it does suggest something important: habitual napping may be linked to better preservation of overall brain volume.
What the Study Did Not Find
This is where I want to be very precise — because this is where most coverage of studies like this goes off the rails.
The study did not show that napping made people smarter. It did not show that napping improved memory, improved reaction time, or produced a larger hippocampal volume.
That last point matters because the hippocampus is one of the key brain structures involved in memory. So if you were expecting naps to show up strongly in memory-related brain regions, that did not happen here.
The study found an association with total brain volume — but not with the cognitive tests they measured, specifically reaction time and visual memory.
So the honest interpretation is not: "Napping makes you smarter."
It is: habitual daytime napping was associated with larger total brain volume, but not better performance on the cognitive tests measured in this study.
That is still interesting. It is just more honest. And honestly, that is the kind of science worth talking about.
Why Brain Volume Matters
Total brain volume is one of the markers researchers use when studying brain aging and neurodegeneration. As we age, the brain naturally loses volume. Some of that is expected. But accelerated brain volume loss is seen in cognitive decline and neurodegenerative disease.
So when researchers find a measurable difference in total brain volume, especially using a method designed to test causal relationships, it is worth taking seriously.
But we also have to keep the meaning in context. Brain volume is not the same thing as memory. It is not the same thing as dementia prevention. It is not the same thing as day-to-day cognitive performance. It is one structural marker, one piece of the brain health puzzle.
The broader literature supports the idea that preserving brain volume matters for cognitive aging, but this specific study did not prove that napping prevents cognitive decline. That distinction matters.
The Biggest Caveat
The UK Biobank data did not capture nap length or timing well. So this study cannot tell us whether a 15-minute nap and a 2-hour nap produce the same outcomes, or very different ones. The authors specifically flag this as a major limitation requiring future research.
A short nap after lunch is not the same as accidentally falling asleep for hours because someone is chronically sleep deprived. And napping because someone feels refreshed afterward is not the same as needing daily naps because of untreated sleep apnea, depression, medication side effects, or poor nighttime sleep.
The study gives us a signal. It does not give us a nap prescription.
A Practical Educational Framework
This is not a personal sleep prescription. But based on this study and the broader sleep literature, here is a cautious way to think about naps educationally.
My Neurologist Take
I would not tell everyone to start taking daily naps based on one study. That is not how medicine works. But I also would not tell someone who sleeps well at night and benefits from a short afternoon rest to feel guilty about it.
What this study adds is valuable: a large genetic analysis suggesting that habitual daytime napping may be linked to a structural marker of brain health.
Not a miracle. Not a dementia cure. Not a replacement for healthy nighttime sleep. But a real signal.
And in a world where people are constantly trying to optimize their brains with expensive supplements, devices, and routines sometimes the brain does not need another productivity hack.
Sometimes it needs recovery.
This study does not prove that naps prevent dementia, improve memory, or that everyone should nap.
But it does suggest that people genetically predisposed to habitual daytime napping have larger total brain volume — a structural marker associated with brain health and aging.
So the next time someone feels guilty about a short afternoon nap, maybe the better question is not: Why am I being lazy?
Maybe it is: What is my brain asking for?
Paz V, Dashti HS, Garfield V. Is there an association between daytime napping, cognitive function, and brain volume? A Mendelian randomization study in the UK Biobank. Sleep Health. 2023;9(5):786–793. PMID: 37344293. doi:10.1016/j.sleh.2023.05.002
This article is for educational purposes only. It is not medical advice, a diagnosis, or a treatment recommendation. It should not be used to start, stop, or change any sleep routine or medical treatment. Individual sleep needs vary. Please consult your own clinician for personal medical concerns.
