Taking a siesta or midday nap is a common custom in some cultures. While previous studies have argued that sleeping in the middle of the day could potentially affect sleep quality, cognitive functioning, and metabolic processes, the relationship between different types of siestas and metabolic health is still poorly understood.
To clarify these issues, a team of researchers led by Brigham and Women’s Hospital has recently assesses the relationship of siestas and siesta duration with obesity and metabolic syndrome in a cohort of 3,275 adults from the Spanish region of Murcia. The experts measured baseline metabolic characteristics, and surveyed the participants on their siesta duration (no siesta, shorter than 30 minutes, longer than 30 minutes), along with other lifestyle factors.
“Not all siestas are the same. The length of time, position of sleep, and other specific factors can affect the health outcomes of a nap,” said senior author Marta Garaulet, a visiting professor in the Brigham’s Division of Sleep and Circadian Disorders.
“A previous study that we conducted in a large study population in the UK had found that siestas were associated with an increased risk of obesity. We wanted to determine whether this would hold true in a country where siestas are more culturally embedded, in this case Spain, as well as how the length of time for siestas is related to metabolic health.”
The analysis revealed that people who took afternoon naps longer than 30 minutes were more likely to have a higher body mass index, higher blood pressure, and a cluster of other conditions associated to heart disease and diabetes (metabolic syndrome) compared to those who took no siestas. Moreover, long siestas were linked to later nightly sleeping and food timing, as well as increased energy intake at lunch and cigarette smoking.
However, among individuals who took shorter siestas, or “power naps,” the increased risk of obesity and metabolic changes was not present. In addition, short siesta-takers seemed to be less likely to have elevated systolic blood pressure than those who took no siestas at all.
Further studies are needed to investigate the possible benefits of short siestas, particularly in individuals with habits such as having delayed meals and sleep schedules, or smoking.
“This study shows the importance of considering siesta length and raises the question whether short naps may offer unique benefits. Many institutions are realizing the benefits of short naps, mostly for work productivity, but also increasingly for general health,” said co-author Frank Scheer, a senior neuroscientist and professor of Medical Chronobiology at the Brigham’s Division of Sleep and Circadian Disorders.
“If future studies further substantiate the advantages of shorter siestas, I think that that could be the driving force behind the uncovering of optimal nap durations, and a cultural shift in the recognition of the long-term health effects and productivity increases that can amount from this lifestyle behavior,” he concluded.
The study is published in the journal Obesity.