Teenagers : more physical activity than usually contributes sleep earlier – longer – better


Getting more exercise than normal – or being more sedentary than usual – for one day may be enough to affect sleep later that night, according to a new study led by Penn State.

In a one-week micro-longitudinal study, the researchers found that when teenagers got more physical activity than they usually did, they got to sleep earlier, slept longer and slept better that night.

Specifically, the team found that for every extra hour of moderate-to-vigorous physical activity, the teens fell asleep 18 minutes earlier, slept 10 minutes longer and had about one percent greater sleep maintenance efficiency that night.

“Adolescence is a critical period to obtain adequate sleep, as sleep can affect cognitive and classroom performance, stress, and eating behaviors,” said Lindsay Master, data scientist at Penn State. “

Our research suggests that encouraging adolescents to spend more time exercising during the day may help their sleep health later that night.”

In contrast, the researchers also found that being sedentary more during the day was associated with worse sleep health.

When participants were sedentary for more minutes during the day, they fell asleep and woke up later but slept for a shorter amount of time overall.

Orfeu Buxton, professor of biobehavioral health at Penn State, said the findings – published today (May 22) in Scientific Reports – help illuminate the complex relationship between physical activity and sleep.

“You can think of these relationships between physical activity and sleep almost like a teeter totter,” Buxton said.

“When you’re getting more steps, essentially, your sleep begins earlier, expands in duration, and is more efficient.

Whereas if you’re spending more time sedentary, it’s like sitting on your sleep health: sleep length and quality goes down.”

While previous research suggests that adolescents need eight to ten hours of sleep a night, recent estimates suggest that as many as 73 percent of adolescents are getting less than eight.

Previous research has also found that people who are generally more physically active tend to sleep longer and have better sleep quality.

But the researchers said less has been known about whether day-to-day changes in physical activity and sedentary behavior affected sleep length and quality.

Despite the overwhelming consensus that both sufficient sleep and adequate exercise are pivotal in maintaining health, these behaviors are often deprioritized within the typical American lifestyle.

For example, the Centers for Disease Control and Prevention estimate that nearly one-third of adults sleep less than the recommended seven hours per night needed to maintain optimal health [12].

An even larger sleep deficit is observed in teenagers: roughly two-thirds of high-school students, who are advised to sleep eight to ten hours, receive less than eight on school nights [34].

Chronic sleep deprivation has been shown to increase the risk for a host of physical and mental illnesses as well as play a dominant role in motor vehicle accidents [56].

Furthermore, poor sleep and sleep-related disorders have had a significant economic impact, costing businesses and the healthcare system billions of dollars annually [7].

Alongside the lack of sleep, Americans have struggled to engage in the recommended amount of daily exercise.

The 2015 National Health Interview Survey found that, from 1997 to 2015, over one-half of adults failed to meet the federal Physical Activity Guidelines for aerobic physical activity and only one-fifth satisfied the federal guidelines for both aerobic and muscle-strengthening activity [8].

One explanation may stem from the increasing proportion of Americans who do not prioritize leisure-time physical activity.

From 1988 to 2010, one study reported that the number of women who do not exercise recreationally jumped from 19.1% to 51.7% while the fraction of their male counterparts rose from 11.4% to 43.5% [9].

Considering that Booth et al. describe exercise as the “primary prevention against 35 chronic health conditions,” especially cardiovascular disease and related disorders, this drastic reduction in leisure-time physical activity may contribute to the substantial prevalence of lifestyle diseases throughout American society [1011].

It should be of little surprise then that Americans who both lack proper sleep and fail to engage in regular exercise vastly increase their risk for chronic illness.

Is it possible there is a link between these two behaviors?

Since 2011, a significant amount of research has been aimed at understanding the physiology of sleep and the interrelationship between sleep and exercise.

In addition, numerous studies have examined whether interventions involving increased physical activity impact sleep.

The purpose of this report is to summarize the most recent literature exploring (i) how different modalities of exercise influence the subjective and objective qualities of sleep and (ii) the impact sleep quality and duration have on exercise performance.

Additionally, this review will examine the physiological factors by which sleep is mediated and discuss why these factors may be so important in understanding sleep as a biological process.

For this study, the researchers used data from 417 participants in the Fragile Families and Child Wellbeing study, a national cohort from 20 United States cities.

When the participants were 15 years old, they wore accelerometers on their wrists and hips to measure sleep and physical activity for one week.

“One of the strengths of this study was using the devices to get precise measurements about sleep and activity instead of asking participants about their own behavior, which can sometimes be skewed,” Master said.

“The hip device measured activity during the day, and the wrist device measured what time the participants fell asleep and woke up, and also how efficiently they slept, which means how often they were sleeping versus tossing and turning.”

In addition to finding links between how physical activity affects sleep later that night, the researchers also found connections between sleep and activity the following day.

They found that when participants slept longer and woke up later, they engaged in less moderate-to-vigorous physical activity and sedentary behavior the next day.

“This finding might be related to a lack of time and opportunity the following day,” Master said.

“We can’t know for sure, but it’s possible that if you’re sleeping later into the day, you won’t have as much time to spend exercising or even being sedentary.”

Buxton said improving health is something that can, and should, take place over time.

“Becoming our best selves means being more like our best selves more often,” Buxton said. “We were able to show that the beneficial effects of exercise and sleep go together, and that health risk behaviors like sedentary time affect sleep that same night.

So if we can encourage people to engage in more physical activity and better sleep health behaviors on a more regular basis, it could improve their health over time.”

In the future, the researchers will continue to follow up with the participants to see how health and health risk behaviors continue to interact, and how sleep health influences thriving in early adulthood.

Journal information: Scientific Reports
Provided by Pennsylvania State University



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