A recent study has unearthed a potential link between regular daytime napping and overall brain volume. This discovery holds promise for staving off the effects of aging on cognitive health.
The magnitude of this finding is quite huge since it corresponds to the difference in brain volume typically observed between individuals with normal cognitive function and those with mild cognitive impairment. This translates to a substantial discrepancy, equivalent to a brain volume decline of 2.6 to 6.5 years due to the aging process.
The study was conducted using data on genetic polymorphisms extracted from the UK Biobank, an extensive population-level database that integrates health surveys with gene-wide association studies. This unique resource enabled the researchers to establish connections between self-reported habits and genetic variations, shedding light on potential associations with disease outcomes.
In this study, recently published in Sleep Health, the authors honed in on a core set of 92 single-nucleotide polymorphisms (SNPs) to identify individuals genetically predisposed to daytime napping. Those found to possess these SNPs were then categorized into groups based on their responses to a question regarding the frequency of daytime napping – ranging from “never” to “rarely,” “sometimes” and “often.”
The role of genetic predisposition is pivotal, as some individuals never experience sufficient daytime fatigue to necessitate naps, a phenomenon that has been linked to higher baseline brain volumes in previous studies.
Quality and duration of sleep play crucial roles in the rate of cognitive decline, cognitive function, and total brain mass. Unfortunately, these factors tend to deteriorate with age, coinciding with the aging process’s impact on cognitive abilities and brain volume.
Additionally, the frequency of daytime napping tends to increase with age after 60. For these reasons, the authors explain that the research on the effects of napping is vital to understanding cognitive decline in later years.
The study analyzed data from over 350,000 participants from the UK Biobank, with an average age of 57. The researchers found a causal relationship between genetically predisposed daytime napping and a notable increase in brain volume, amounting to 15.3 cubic centimeters, or approximately a 1.6% difference.
The study also examined the hippocampus volume, visual memory and reaction time as secondary measures. Surprisingly, none of these factors showed any discernable association with habitual daytime napping, which perplexed the scientific community since the hippocampus is where short-term visual memory is processed and made into long-term memory storage.
“Our hypothesis was based on the fact that the hippocampus, as a brain structure that plays a crucial role in memory, could be a useful proxy of the variations in memory performance reported to be associated with daytime napping. However, we did not find this association, nor an association between genetic liability to habitual daytime napping and visual memory performance,” the authors wrote.
The main takeaway from the study is that more research is still needed. However, the findings also suggest that for those genetically predisposed to habitual daytime naps – meaning those that feel the urge to nap during the daytime – it could actually be a “natural defense” against cognitive decline as they age.
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