Longer naps linked to higher risk of obesity and high blood pressure

[Apr. 28, 2023: JD Shavit, The Brighter Side of News]

Taking a siesta or midday nap is a common practice in some countries, and is often seen as a way to recharge and boost productivity. However, the effects of siestas on health have been a subject of debate for years.

While some studies have suggested that taking a nap in the middle of the day can improve cognitive function and reduce stress, others have linked it to increased risk of obesity, heart disease, and diabetes. Now, a new study conducted by researchers from Brigham and Women’s Hospital sheds more light on this issue, revealing that long siestas may be linked to higher BMI and metabolic syndrome.

The study, which was published in Obesity, involved over 3,000 adults from a Mediterranean population, specifically people from the Spanish region of Murcia. The researchers examined the relationship between siestas and metabolic health by measuring baseline metabolic characteristics and collecting data on participants’ siesta habits and other lifestyle factors.

They 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.

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“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, PhD, 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 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.”

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 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.

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.

Dr. Garaulet explained that the finding that short naps may offer unique benefits is consistent with previous studies that have shown that brief periods of sleep can have a restorative effect on cognitive function and overall health. “In our previous studies, we have found that short naps can improve cognitive performance and reduce the risk of developing cardiovascular disease,” she said.

The researchers also noted that the cultural context in which siestas are taken may play a role in their impact on health. In Spain, for example, siestas are part of the culture and are seen as a way to recharge and increase productivity during the day. However, in other cultures, taking a midday nap may be seen as a sign of laziness or unproductivity, which could lead to feelings of guilt or shame.

The study has important implications for public health, as it highlights the potential risks and benefits of taking siestas. According to the World Health Organization, obesity is a major risk factor for a range of chronic diseases, including cardiovascular disease, diabetes, and certain cancers. Metabolic syndrome, which is characterized by a cluster of conditions including high blood pressure, high blood sugar, and excess body fat around the waist, is also a significant risk factor for these diseases.

The researchers recommend that individuals who take siestas should be mindful of the duration of their naps and the context in which they are taken. They suggest that short naps may offer unique benefits, particularly for those with delayed meal and sleep schedules, or for those who smoke. Additionally, they recommend that future research investigate the potential benefits of incorporating short naps into workplace policies and public health campaigns.

Dr. Scheer added that the study highlights the need for a cultural shift in how siestas are viewed. “Many institutions are realizing the benefits of short naps, mostly for work productivity, but also increasingly for general health,” he said. “If future studies further substantiate the advantages of shorter siestas, I think 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 study, which was funded by the National Institute of Diabetes and Digestive and Kidney Diseases and the National Heart, Lung, and Blood Institute, is part of a larger effort to better understand the relationship between lifestyle factors and metabolic health. The researchers plan to continue investigating the impact of sleep and other lifestyle factors on health outcomes, with the ultimate goal of developing strategies to improve public health and reduce the burden of chronic disease.

Note: Materials provided above by The Brighter Side of News. Content may be edited for style and length.

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