NEW YORK, Oct 29, (Agencies): Despite our innate inclination to nap, the direct connection between daytime napping and brain health has remained elusive. A groundbreaking new study conducted by researchers from the University College London in the UK, the University of the Republic in Uruguay, and the Broad Institute in Massachusetts has employed a novel analytical technique to delve into the causal relationships in this domain.

The primary objective of this new study was to investigate a potential link between a genetic disposition towards napping and brain volume, which is widely regarded as an indicator of overall brain health. This rigorous examination of the subject involved the analysis of data from a substantial pool of 378,932 participants in the UK Biobank, with an age range spanning from 40 to 69, and an average age of 57.

Within this extensive dataset, the researchers identified individuals harboring 92 genetic variants previously associated with habitual napping. They also measured various factors such as brain volume, hippocampal volume, reaction time, and visual memory for those individuals with these genetic markers. The utilization of the Mendelian randomization technique revealed compelling associations that the study's authors have reported.

The most noteworthy revelation from this research suggests that individuals possessing these specific genetic characteristics are more likely to exhibit a higher brain volume. As a reduced brain volume is often associated with neurodegeneration in the form of atrophy due to cell death, maintaining a healthy brain volume is considered a positive sign of one's overall health.

Napping is an ingrained activity in numerous cultures worldwide, with millions of individuals taking brief daytime respites. While some may grapple with feelings of guilt associated with midday siestas, existing research hints at the potential value of napping. A 2016 study revealed cognitive benefits stemming from short naps, typically lasting between 30 minutes to 90 minutes. These brief naps were found to leave individuals more alert and mentally sharp upon waking. However, the same research highlights the cognitive challenges that may arise from prolonged napping.

Despite the advancements in research on napping, the long-term relationship between napping and cognitive health remains a subject of uncertainty. For instance, one study found a potential heightened risk of Alzheimer's among cognitively healthy nappers, while another study reached the opposite conclusion.

Valentina Paz, the lead author of the study, a Ph.D. candidate, and an assistant professor of psychology at the University of the Republic in Uruguay, commented, "This is the first study to attempt to untangle the causal relationship between habitual daytime napping and cognitive and structural brain outcomes. By examining genes determined at birth, Mendelian randomization minimizes the influence of confounding factors that may arise throughout one's lifetime."

In a recent interview with Medical News Today, Dr. Paz disclosed that her study specifically identified a significant increase in total brain volume, equivalent to 15.8 cm3 (cubic centimeters), associated with more frequent daytime napping. Dr. Paz framed this finding as roughly akin to the aging difference of 2.6 to 6.5 years. Nevertheless, she cautioned that further research is required to unravel this association completely.

Mendelian randomization is a technique that leverages genetic variation to explore the causal relationships between modifiable exposures and various outcomes. However, as Dr. Penelope Lewis, a professor at the School of Psychology at the University of Cardiff, aptly pointed out, it may be premature to assert a direct causal link between napping and brain size, as it might merely indicate a correlation.

One essential point to note is that this study did not directly assess the cognitive benefits of napping, nor did it focus on nappers themselves. Instead, its focus was strictly on individuals with a genetic predisposition to napping. Dr. Rebecca Spencer, a professor of neuroscience at the University of Massachusetts Amherst, voiced concerns about the lack of specific data regarding the napping habits of the participants. In the UK Biobank survey, respondents were asked if they napped during the day, with three possible responses: "never/rarely," "sometimes," or "usually." This approach was criticized as subjective, and it also failed to specify the time frames for reporting napping habits, which Dr. Spencer argued could span anywhere from the past week to one's lifetime.

Furthermore, the study did not provide a standardized definition of a nap or establish a specific duration for napping. Dr. Lewis mentioned that slow-wave sleep plays a critical role in brain health, as it helps flush toxins from the brain, and a loss of slow-wave sleep is associated with cortical atrophy. She speculated that naps containing slow-wave sleep might contribute to preserving cognitive health and staving off atrophy.

While the traditional perception is that dreams are mainly associated with REM sleep rather than deep, slow-wave sleep, recent research suggests that dreaming can occur even during slow-wave sleep. Dr. Paz underscored that her findings represent a significant step toward understanding the relationship between daytime napping frequency and brain health. However, she acknowledged that more research is necessary to fully comprehend this complex connection.

While Dr. Lewis commended the study for providing new insights into the ongoing investigation of napping and sleep's effects, she remained cautious about making blanket statements regarding the benefits of napping for brain health. She highlighted the potential risks, such as poor overnight sleep, associated with excessive napping. Dr. Lewis ultimately emphasized the critical importance of getting an adequate amount of sleep within a 24-hour cycle for overall health and well-being.

In summary, the study conducted by researchers from the University College London, the University of the Republic in Uruguay, and the Broad Institute in Massachusetts has shed light on the complex relationship between genetics, daytime napping, and brain health. While it provides valuable insights, the field remains ripe for further investigation and exploration.