Once or twice weekly daytime nap linked to lower heart attack/stroke risk

But no such association found for greater frequency or duration of naps

September 9, 2019

Science Daily/BMJ

A daytime nap taken once or twice a week may lower the risk of having a heart attack/stroke, finds research published online in the journal Heart. But no such association emerged for either greater frequency or duration of naps.

The impact of napping on heart health has been hotly contested. Many of the published studies on the topic have failed to consider napping frequency, or focused purely on cardiovascular disease deaths, or compared regular nappers with those not opting for a mini siesta, say the researchers.

In a bid to try and address these issues, they looked at the association between napping frequency and average nap duration and the risk of fatal and non-fatal cardiovascular disease 'events,' such as heart attack, stroke, or heart failure, among 3462 randomly selected residents of Lausanne, Switzerland.

Each participant was aged between 35 and 75, when recruited between 2003 and 2006 to the CoLaus study. This has been looking at the factors behind the development of cardiovascular disease.

Participants' first check-up took place between 2009 and 2012, when information on their sleep and nap patterns in the previous week was collected, and their health was then subsequently monitored for an average of 5 years.

Over half (58%, 2014) of the participants said they didn't nap during the previous week; around one in five (19%, 667) said they took one to two naps; around one in 10 (12%, 411) said they took three to five; while a similar proportion (11%, 370) said they took six to seven.

Frequent nappers (3-7 naps a week) tended to be older, male, smokers, weigh more, and to sleep for longer at night than those who said they didn't nap during the day.

And they reported more daytime sleepiness and more severe obstructive sleep apnea -- a condition in which the walls of the throat relax and narrow during sleep, interrupting normal breathing.

During the monitoring period, there were 155 fatal and non-fatal cardiovascular disease 'events'.

Occasional napping, once to twice weekly, was associated with an almost halving in attack/stroke/heart failure risk (48%) compared with those who didn't nap at all.

This association held true after taking account of potentially influential factors, such as age, and nighttime sleep duration, as well as other cardiovascular disease risks, such as high blood pressure/cholesterol.

And it didn't change after factoring in excessive daytime sleepiness, depression, and regularly sleeping for at least 6 hours a night. Only older age (65+) and severe sleep apnea affected it.

But the 67% heightened cardiovascular risk initially observed for frequent nappers virtually disappeared after taking account of potentially influential factors. And no associations with cardiovascular disease 'events' were found for nap length (from 5 minutes to 1 hour plus).

This is an observational study, and as such, can't establish cause, added to which the information on nap and sleep patterns relied on personal recall. But nap frequency may help to explain the differing conclusions reached by researchers about the impact of napping on heart health, suggest the study authors.

In a linked editorial, Drs Yue Leng and Kristine Yaffe, of the University of California at San Francisco, USA, point out that research in this area is hampered by the absence of a gold standard for defining and measuring naps, making it "premature to conclude on the appropriateness of napping for maintaining optimal heart health."

But they add: "While the exact physiological pathways linking daytime napping to [cardiovascular disease] risk is not clear, [this research] contributes to the ongoing debate on the health implications of napping, and suggests that it might not only be the duration, but also the frequency that matters."

And they conclude: "The study of napping is a challenging but also a promising field with potentially significant public health implications. While there remain more questions than answers, it is time to start unveiling the power of naps for a supercharged heart."

https://www.sciencedaily.com/releases/2019/09/190909193219.htm

School children who nap are happier, excel academically, and have fewer behavioral problems

May 31, 2019

Science Daily/University of Pennsylvania

Children who nap 30 to 60 minutes midday at least three times a week are happier, have more self-control and grit, and showcase fewer behavioral problems, according to new research. These children also have higher IQs and excel academically.

Ask just about any parent whether napping has benefits and you'll likely hear a resounding "yes," particularly for the child's mood, energy levels, and school performance. New research from the University of Pennsylvania and the University of California, Irvine, published in the journal SLEEP backs up that parental insight.

A study of nearly 3,000 fourth, fifth, and sixth graders ages 10-12 revealed a connection between midday napping and greater happiness, self-control, and grit; fewer behavioral problems; and higher IQ, the latter particularly for the sixth graders. The most robust findings were associated with academic achievement, says Penn neurocriminologist Adrian Raine, a co-author on the paper.

"Children who napped three or more times per week benefit from a 7.6% increase in academic performance in Grade 6," he says. "How many kids at school would not want their scores to go up by 7.6 points out of 100?"

Sleep deficiency and daytime drowsiness are surprisingly widespread, with drowsiness affecting up to 20% of all children, says lead author on the study Jianghong Liu, a Penn associate professor of nursing and public health. What's more, the negative cognitive, emotional, and physical effects of poor sleep habits are well-established, and yet most previous research has focused on preschool age and younger.

That's partially because in places like the United States, napping stops altogether as children get older. In China, however, the practice is embedded into daily life, continuing through elementary and middle school, even into adulthood. So, Liu and Raine, with Penn biostatistician Rui Feng, UC Irvine sleep researcher Sara Mednick and others, turned to the China Jintan Cohort Study, established in 2004 to follow participants from toddlerhood through adolescence.

From each of 2,928 children, the researchers collected data about napping frequency and duration once the children hit Grades 4 through 6, as well as outcome data when they reached Grade 6, including psychological measures like grit and happiness and physical measures such as body mass index and glucose levels. They also asked teachers to provide behavioral and academic information about each student. They then analyzed associations between each outcome and napping, adjusting for sex, grade, school location, parental education, and nightly time in bed.

It was the first comprehensive study of its kind, Mednick says. "Many lab studies across all ages have demonstrated that naps can show the same magnitude of improvement as a full night of sleep on discrete cognitive tasks. Here, we had the chance to ask real-world, adolescent schoolchildren questions across a wide range of behavioral, academic, social, and physiological measures."

Predictably, she adds, "the more students sleep during the day, the greater the benefit of naps on many of these measures."

Though the findings are correlational, the researchers say they may offer an alternative to the outcry from pediatricians and public health officials for later school start times. "The midday nap is easily implemented, and it costs nothing," says Liu, particularly if accompanied by a slightly later end to the day, to avoid cutting into educational time. "Not only will this help the kids, but it also takes away time for screen use, which is related to a lot of mixed outcomes."

Future directions could look at why, for example, children with better-educated parents nap more than children with less educated parents, or whether, by investigating the influence of culture and personality, nap interventions could be advanced on a global scale. Ideally, a randomized control trial would get at causation questions like whether napping leads to better academic achievement or whether they're linked in some other way. However, none of this is yet in the works.

For now, the researchers say they hope the results of this current study can inform future interventional work that targets adolescent sleepiness.

https://www.sciencedaily.com/releases/2019/05/190531135828.htm