Researchers discovered through analyzing data that individuals who engage in lengthy siestas tend to have higher body mass indexes and a greater likelihood of having metabolic syndrome compared to those who do not take siestas.
It is a common practice in some countries to take a midday nap, known as a siesta. Despite its potential to impact sleep quality, cognitive performance, and metabolic processes, the connection between siestas and metabolic health remains unclear.
A recent study conducted by researchers from Brigham and Women’s Hospital, a member of the Mass General Brigham healthcare system, evaluated the link between siestas, siesta duration, and obesity and metabolic syndrome in over 3,000 adults from a Mediterranean population.
The researchers found that those who took siestas of 30 minutes or longer (long siestas) were more likely to have a higher body mass index, higher blood pressure, and a cluster of other conditions associated with heart disease and diabetes (metabolic syndrome) compared to those without siestas.
However, for those who had short siestas, also known as “power naps,” this increased risk for obesity and metabolic alterations was not present. In contrast, short siesta-takers were less likely to have elevated systolic blood pressure than those who took no siestas. The team’s results are published in the journal Obesity.
Understanding Siestas in a Cultural Context
“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, Ph.D., a visiting professor in the Division of Sleep and Circadian Disorders at Brigham and Women’s Hospital.
“A previous study that we conducted in a large study population in the UK 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.”
Obesity is a growing health concern affecting over one billion people around the world. Fat accumulation in the body is connected to how food is digested during metabolic processes. Understanding how lifestyle choices, such as taking siestas, affect these metabolic mechanisms could help researchers learn how habits influence health.
The researchers examined data from 3,275 adults in a Mediterranean population, specifically people from the Spanish region of Murcia. Baseline metabolic characteristics were measured for the participants at the University of Murcia and a survey on siestas collected additional details regarding their naps and other lifestyle factors.
This resulted in the categories of no siestas, shorter than 30 minutes, and longer than 30 minutes.
The research team found that long siesta-takers had a higher body mass index and were more likely to have metabolic syndrome (MetS) than those who did not take siestas. Additionally, compared with the no-siesta group, the long siesta group had higher values of waist circumference, fasting glucose levels, systolic blood pressure (SBP), and diastolic blood pressure.
Lifestyle Factors Affecting Siesta Risks
The researchers found that long siestas were associated with later nightly sleep timing and food timing, with increased energy intake at lunch and cigarette smoking, and with the location of siestas (a bed vs. a sofa), which may explain the higher risks associated with longer duration siestas.
While this is an observational study and it is possible that some factors may be a consequence of obesity and not siestas per se, a previous study of the data collected in the UK Biobank pointed to a causal relationship between napping and obesity, particularly with abdominal obesity, the most detrimental form.
In the current study, the authors found a variety of statistically significant lifestyle factors mediating the association between siestas and health measures.
The results of the study call for future research to investigate whether a short siesta is advantageous over a long one, particularly for individuals with habits such as having delayed meals and sleep schedules, or for those who smoke.
“This study shows the importance of considering siesta length and raises the question of 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. 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,” said co-author Frank Scheer, Ph.D., a senior neuroscientist and professor in the Medical Chronobiology Program in the Brigham’s Division of Sleep and Circadian Disorders.
Reference: “Lifestyle mediators of associations among siestas, obesity, and metabolic health” by Barbara Vizmanos, Ana Isabel Cascales, María Rodríguez-Martín, Diego Salmerón, Eva Morales, Aurora Aragón-Alonso, Frank A. J. L. Scheer and Marta Garaulet, 26 April 2023, Obesity.
DOI: 10.1002/oby.23765
Disclosures: Frank A.J.L. Scheer served on the Board of Directors for the Sleep Research Society and has received consulting fees from the University of Alabama at Birmingham. Frank A.J.L. Scheer interests’ were reviewed and managed by Brigham and Women’s Hospital and Partners HealthCare in accordance with their conflict of interest policies. Frank A.J.L. Scheer’s consultancies are not related to the current work. The other authors declared no conflict of interest.
The study was funded by Comunidad Autonoma de la Region de Murcia, Seneca Foundation, Consejo Nacional de Ciencia y Tecnología, Ministerio de Ciencia e Innovation, the National Heart, Lung, and Blood Institute, the National Institute of Diabetes and Digestive and Kidney Diseases and Universidad de Guadalajara.
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