A 2023 study in Sleep Health analyzed the data of 35,080 people aged 40 to 69 from a U.K. Biobank study. Researchers found a link between frequent daytime napping and as much as 15.8 cm3 (cubic centimeters) increase in total brain volume. That’s 2.5 to 6.5 years of aging. 

The study didn’t examine cognitive performance, but it used a randomized research method focused on genetics called Mendelian randomization, which looked at DNA samples and brain scans of the participants. As explained by Valentina Paz, lead author and researcher at the University of the Republic of Uruguay and University College London (UCL), “By looking at genes set at birth, Mendelian randomisation avoids confounding factors occurring throughout life that may influence associations between napping and health outcomes. Our study points to a causal link between habitual napping and larger total brain volume.” This study has faced its share of criticism, however, with some experts critiquing its lack of accurate data regarding napping length and others pointing to the absence of cognitive evaluation. Moreover, correlation doesn’t necessarily mean causation. 

While we may not know exactly what happens to the size of your brain when you snooze on the couch after a hearty pasta salad lunch, what we do know is that taking a nap or choosing not to is a very subjective thing, which brings us to the next set of questions: Should you be napping? And if so, for how long?