Napping for over an hour linked to obesity and high blood pressure

By James Gamble via SWNS

Nappers who sleep more than half an hour in the middle of the day are more likely to be obese or suffer from high blood pressure, a new study has found.

Longer siesta-takers in Spain were more likely to have a higher Body Mass Index (BMI), higher blood pressure and a cluster of other conditions linked with heart disease and diabetes.

Meanwhile, those who instead took "power naps" of less than 30 minutes were found to avoid these increased health risks and even fared better in terms of blood pressure than those who abstained from taking siestas.

The researchers, based in the United States, concluded that, incredibly, the length of your siesta could be vitally important not only for work productivity but also for our general health.

The term "siesta" comes from the Latin word "sexta," meaning sixth, and refers to the "sexta hora" or sixth hour of the day.

The indulgent naps, usually taken following the midday meal, have been commonplace for centuries in warmer climates such as the Mediterranean and Latin America.

In Spain, where the tradition is believed to have originated, most businesses still close between the hours of two and four pm, so employees can rest during the hottest period of the day.

The regenerative powers of the siesta have today spread to all corners of the globe and have been embraced by U.S. Presidents such as John F. Kennedy and German physicists like Albert Einstein.

The study team, from the Brigham and Women's Hospital - part of the Harvard Medical School in the United States - analyzed data collected from 3,275 Spanish adults from the city of Murcia in the southeastern part of the country.

Though a previous study conducted in the UK indicated a causal relationship between napping and obesity, the U.S. researchers considered it important to conduct further research amongst a population in which siestas were more culturally embedded.

Baseline metabolic characteristics of the participants were measured at the University of Murcia and a survey on siestas collected details regarding the participants' naps as well as other lifestyle factors.

The data on siestas resulted in the participants being split into three groups: those who took no siestas, those who took siestas for less than half an hour and those whose siestas lasted more than half an hour.

The researchers found that those who took the longer siestas had higher BMIs and were more likely to have metabolic syndrome - a group of conditions that raise the risk of heart disease, diabetes, stroke, and other serious health problems - compared with Spaniards who did not take siestas.

The long-siesta group were also found to have higher values of waist circumference, fasting glucose levels, systolic blood pressure and diastolic blood pressure than those who didn't take siestas.

The study team additionally highlighted the association of longer siesta takers with later nightly sleep and meal times, increased energy intake at lunchtimes and even cigarette smoking.

They even found a link between those who took longer naps and the location of their siesta - with many opting for a fully-horizontal lie-down on their beds rather than a sofa.

However, in those who took siestas for less than half an hour a day, these increased risks of obesity and metabolic health problems simply did not exist.

In fact, the short siesta-takers were found to be less likely to have elevated systolic blood pressure than those who took no siestas at all.

Despite the researchers admitting that some factors may be a consequence of obesity rather than of the siestas themselves, the previous UK study pointing towards a similar relationship between napping and obesity - particularly abdominal obesity - further fortified these latest findings.

In this latest study, the authors also discovered a variety of significant lifestyle factors mediating the association between siestas and health measures.

The results, say the study team, call for future research into whether shorter siestas are advantageous over longer ones - particularly for those with habits such as smoking and having delayed nighttime meals and rest.

Senior author Marta Garaulet, a visiting professor in the Division of Sleep and Circadian Disorders at Brigham and Women's Hospital said: "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.

"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 in Spain - as well as how the length of time for siestas is related to metabolic health."

Co-author Dr. Frank Scheer, a senior neuroscientist and professor in the Medical Chronobiology Program at Brigham’s Division of Sleep and Circadian Disorders, argued the increasingly evident benefits of taking shorter naps.

He said: "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."

The Harvard team's study was published in the scientific journal Obesity.