Longer Midday Naps Linked to Increased Risk of Metabolic Syndrome

Marta Garaulet, PhD
Credit: Harvard University

A new study is sounding the alarm on the risk of obesity, metabolic syndrome, and hypertension associated with longer durations of daytime naps.

Results of the study, which was conducted by investigators within the Mass General Brigham health system, indicate increased duration of siestas, or midday napping, was associated with a greater level of BMI, waist circumference, fasting glucose, diastolic blood pressure, and systolic blood pressure.

“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 investigator Marta Garaulet, PhD, a visiting professor in the Division of Sleep and Circadian Disorders at Brigham and Women's Hospital.² “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 burden placed on health systems by the obesity epidemic has been unmatched in modern times, with this crisis only expected to worsen in the coming years and decades.³ In the past several years, research has begun to emerge outlining the potential for increased risk of cardiovascular disease and all-cause mortality.⁴

In the current study, Garaulet and a team of colleagues sought to assess whether longer midday naps were associated with increased risk of metabolic syndrome. With this in mind, investigators designed their study as a cross-sectional analysis of patients from within the ONTIME study, which included more than 3000 adult patients from a Mediterranean population. For the purpose of analysis, siesta duration was used as the primary exposure, with long naps considered more than 30 minutes and short naps considered 30 minutes or less.¹

This cohort had a mean age of 41 (SD, 12) years, 78% were women, and the mean BMI was 31 (SD, 6) kg/m2. Overall, 87.4% of the population had overweight or obesity. Of the more than 3000 participants, 35% reported taking habitual siestas, with this cohort averaging 4 naps per week and a similar duration on weekdays and weekends. Overall, 16% reported taking long siestas and 20% reported taking short siestas.¹

Upon analysis, results indicated long siestas were associated with increased values of BMI, waist circumference, fasting glucose, systolic blood pressure, and diastolic blood pressure, as well as with a higher prevalence of metabolic syndrome (41%; P=.015). However, investigators pointed out the probability of having elevated systolic blood pressure was lower in the short-siesta group than among the no-siesta group (21%; P=.044).¹

Further analysis indicated smoking a high number of cigarettes per day mediated the association of long siestas with higher BMI by 12% (P <.05). Investigators pointed out delays in nighttime sleep and eating schedules as well as higher energy intake at lunch mediated the association between elevated BMI and long siestas by 8%, 4%, and 5% (all P <.05). Investigators also noted a trend towards mediation of the association between long siestas and elevated systolic blood pressure observed with napping in bed as opposed to napping on a sofa or armchair (6%; P=.055).¹

“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. 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 study investigator Frank Scheer, PhD, a senior neuroscientist and professor in the Medical Chronobiology Program in the Brigham’s Division of Sleep and Circadian Disorders.²

References:

1. Vizmanos B, Cascales AI, Rodriguez-Martin M. Lifestyle mediators of associations among siestas, obesity, and metabolic health. Obesity. Published April 26, 2023. Accessed April 26, 2023. doi:10.1002/oby.23765.
2. Brigham and Women's Hospital. Longer siestas linked to higher risk of obesity, metabolic syndrome, and high blood pressure. Newswise. https://www.newswise.com/articles/longer-siestas-linked-to-higher-risk-of-obesity-metabolic-syndrome-and-high-blood-pressure. Published April 25, 2023. Accessed April 26, 2023.
3. Yang MJ, Zhang Z, Wang YJ, et al. Association of Nap Frequency with Hypertension or Ischemic Stroke Supported by Prospective Cohort Data and Mendelian Randomization in Predominantly Middle-Aged European Subjects. Hypertension. 2022;79(9):1962-1970. doi:10.1161/HYPERTENSIONAHA.122.19120
4. Adult obesity facts. Centers for Disease Control and Prevention. https://www.cdc.gov/obesity/data/adult.html. Published May 17, 2022. Accessed April 26, 2023.