Study: Texting negatively affects teen's sleep and academic performance

A study shows that teenagers who text at night hurts their sleep and academic performance.

Can't stop texting? If you're a teenager, it may be to blame for falling grades and increased yawning in school, according to a new Rutgers study.

The study, published in the Journal of Child Neurology, is the first of its kind to link nighttime instant messaging habits of American teenagers to sleep health and school performance.

"We need to be aware that teenagers are using electronic devices excessively and have a unique physiology," says study author Xue Ming, professor of neuroscience and neurology at Rutgers New Jersey Medical School. "They tend to go to sleep late and get up late. When we go against that natural rhythm, students become less efficient."

The American Academy of Pediatrics reports that media use among children of all ages is increasing exponentially; studies have found that children ages 8 to 18 use electronic devices approximately seven-and-a-half hours daily.

Ming's research is part of a small but growing body of evidence on the negative effects of electronics on sleep and school performance. But few studies, Ming says, have focused specifically on instant messaging.

"During the last few years I have noticed an increased use of smartphones by my patients with sleep problems," Ming says. "I wanted to isolate how messaging alone - especially after the lights are out - contributes to sleep-related problems and academic performance."

To conduct her study, Ming distributed surveys to three New Jersey high schools - a suburban and an urban public school and a private school - and evaluated the 1,537 responses contrasting grades, sexes, messaging duration and whether the texting occurred before or after lights out.

She found that students who turned off their devices or who messaged for less than 30 minutes after lights out performed significantly better in school than those who messaged for more than 30 minutes after lights out.

Students who texted longer in the dark also slept fewer hours and were sleepier during the day than those who stopped messaging when they went to bed. Texting before lights out did not affect academic performance, the study found.

Although females reported more messaging overall and more daytime sleepiness, they had better academic performance than males. "I attribute this to the fact that the girls texted primarily before turning off the light," Ming says.

The effects of "blue light" emitted from smartphones and tablets are intensified when viewed in a dark room, Ming says. This short wavelength light can have a strong impact on daytime sleepiness symptoms since it can delay melatonin release, making it more difficult to fall asleep - even when seen through closed eyelids.

"When we turn the lights off, it should be to make a gradual transition from wakefulness to sleep," Ming says. "If a person keeps getting text messages with alerts and light emission, that also can disrupt his circadian rhythm. Rapid Eye Movement sleep is the period during sleep most important to learning, memory consolidation and social adjustment in adolescents. When falling asleep is delayed but rising time is not, REM sleep will be cut short, which can affect learning and memory."

Ming notes some benefits to early-evening media use, such as facilitating collaboration for school projects, providing resources for tutoring, increasing school readiness and possibly offering emotional support systems.

She suggests that educators recognize the sleep needs of teenagers and incorporate sleep education in their curriculum. "Sleep is not a luxury; it's a biological necessity. Adolescents are not receiving the optimal amount of sleep; they should be getting 8-and-a-half hours a night," says Ming. "Sleep deprivation is a strong argument in favor of later start times for high schools - like 9 a.m."

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Health consequences of texting in bed

A study indicates that texting in bed can lead to losing sleep in addition to poor school performance in teens.

Many American teens text in bed, leading to lost sleep, daytime drowsiness and poorer school performance, a new study says.

Researchers from New Jersey looked at nearly 3,200 middle and high school students in the state. They found that nearly 62 percent of the kids used their smartphones in some capacity after bedtime; nearly 57 percent texted, tweeted or messaged in bed; and nearly 21 percent awoke to texts.

"Our study confirms that many teenagers are texting late at night when they should be sleeping. This behavior is more common among older teenagers, especially those in high school, and among girls," said study co-author Vincent DeBari. He is director of research at the Seton Hall University School of Health and Medical Sciences, in South Orange.

"One of the most worrisome aspects of our findings is that in addition to affecting the quality and amount of sleep teenagers are getting, bedtime smartphone use seems to be having a negative impact on their level of alertness during the day and on their grades in school," DeBari said in a university news release.

His study co-author, Dr. Peter Polos, added that teens whose sleep is disrupted by incoming texts may feel compelled to respond to those texts immediately. These exchanges can go on for hours.

"This leads to excessive stimulation at night. Light from electronic devices can suppress the secretion of melatonin, a hormone that promotes sleep. All of these factors combine to make sleep difficult in the face of excessive smartphone use at night," said Polos, a member of the sleep medicine division of the JFK Neuroscience Institute in Edison, N.J.

The researchers also found that smartphone use just before or after bedtime may worsen teens' tendency to go to bed much later and sleep until late morning. This behavior has been linked with depression, anxiety and attention-deficit hyperactivity disorder, the study authors said.

"Repeatedly, studies have shown that today's adolescent students are seriously sleep-deprived, and that it affects their health, their mood and their safety behind the wheel. Our study shows that the unrestricted use of smartphones at night may be a major contributing factor," Dr. Sushanth Bhat, an assistant professor of neuroscience at Seton Hall, said in the news release.

"Since getting the proper amount of sleep is very important for brain development and learning in the teenage years, our study should prompt parents and guardians to consider placing reasonable limitations on adolescent smartphone usage at night," Bhat concluded.

The study findings appear in the October issue of the Journal of Adolescence.

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Teenagers in the US are getting less sleep than ever

A study showed that teenagers in the US are getting less sleep than they ever have.

American teens don't get enough sleep, and the problem has only gotten worse since the 1990s, new research shows.

Just 63 percent of 15-year-olds reported getting seven or more hours of sleep a night in 2012. That number is down from 72 percent in 1991, according to the study.

Regardless of the time period studied, the number of teens reporting seven or more hours of sleep nosedives between the ages of 13 and 18, the study showed. At 13, roughly two-thirds of teens get at least seven hours of sleep a night; by 18 that percentage drops to about one-third.

"After age 16, the majority are not meeting the recommended guidelines," said study author Katherine Keyes, an assistant professor of epidemiology at Columbia University's Mailman School of Public Health in New York City.

Sleep experts have noted that too little sleep boosts the risk of weight gain, poor school performance, depression and other problems.

The study is published online Feb. 16 in Pediatrics.

For the study, researchers from Columbia University looked at sleep data from a national survey of more than 270,000 teens from 1991 to 2012. Each year, teens reported how often they got seven or more hours of sleep, as well as how often they got less sleep than they need.

The most recent recommendation from the National Sleep Foundation says teens aged 14 to 17 need eight to 10 hours a night and people aged 18 to 25 need seven to nine hours.

The largest declines in those getting enough sleep occurred between 1991 through 2000; then the problem plateaued, Keyes said.

The researchers also found gender differences in sleep. "Girls are less likely to get an adequate amount of sleep compared to boys," she said.

Both boys and girls whose parents had less education were not as likely to get enough sleep. Keyes found racial differences, too, with black and Hispanic teens less likely than others to get enough sleep.

One worrisome finding, she said, was that some teens who weren't getting enough sleep often thought their sleep duration was fine.

Keyes did not have access to information about the teens' use of electronic media, a factor often blamed for lack of sleep as teens text, check social media, play video games and work on laptops late into the night. However, that might be a factor, she said.

"On an individual level, excessive use of technology may impair an adolescent's ability to sleep," Keyes said.

The study findings aren't surprising, said Dr. Marcel Deray, a pediatric neurologist and director of the sleep disorders center at Miami Children's Hospital.

Deray said that while this study didn't offer information about whether electronic use is to blame for teens' lack of sleep, an American Academy of Pediatrics report in 2014 cited technology, along with caffeine use and other habits, as contributing factors in teen sleep deprivation. Deray said instructing teens to stop all electronic media use by at least an hour before bed might help.

Another issue? Early school start times can play havoc with teens' sleep, according to Deray.

Like some other experts, Deray said later school start times -- even an hour later -- could help teens get more sleep. Teens naturally go to sleep later, he said, due to their sleep cycles and the release of the hormone melatonin. "When we fall asleep, melatonin goes up. Teens make it later, so they tend to be night owls," Deray said.

Left alone, he said, teens would go to sleep later and get up later. Starting school an hour later, for instance at 8:30 a.m., is an approach favored by the American Academy of Pediatrics and would likely help, he added.

Lack of sleep is linked with many other health problems for teens, he said, including obesity, car accidents, depression and a drop in school performance.

Parents of teens can educate their children about not overscheduling, limiting caffeine before bed and having a bedtime routine, just as they did when they were younger, Keyes said.

Deray said teens can also try to get up by 9 a.m. on the weekend and to expose themselves to sunlight in the morning, helping to make them sleepier earlier at night.

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Most US teens are sleep deprived

A recent study shows that most of the teens in the US are sleep deprived.

More than 90 percent of American high school students are chronically sleep-deprived, putting their health and academic performance in jeopardy, a new report finds.

The study, based on U.S. national data, finds that most teens don't get the minimum 9 to 10 hours of sleep per night that's recommended by standard guidelines.

Teenagers do face a number of challenges as they try to get adequate sleep, experts say.

"I don't believe there's one culprit," said the study's lead author, Charles Basch, a professor of health and education at the Teacher's College at Columbia University in New York City.

"For some children it's too much homework, for some it's health problems like asthma," he explained. "For others it may be anxiety or depression, or the prescription medications they are taking for such conditions. Recreational drugs can be a factor, as can having electronics in the bedroom."

Whatever the reason, government surveys show that poor sleep is an ongoing issue for most teenagers.

"This type of data has only been collected since 2007, so we can't say whether the situation has been getting worse historically," Basch said. "But what we can clearly say is that a very substantial portion of high school students throughout America is not getting enough sleep."

His team noted that teens, especially, need adequate sleep because it's crucial to memory, attention, emotional well-being and overall physical health.

In the study, the researchers tracked findings from four U.S. government surveys conducted in 2007, 2009, 2011 and 2013 as part of the Youth Risk Behavior Surveillance System.

Each year, between roughly 12,000 to 15,000 students in grades 9 through 12 were asked about how many average hours of sleep they got each school night.

Overall, less than 10 percent of teens said they were actually meeting current U.S. Centers for Disease Control and Prevention guidelines for sleep. Only about 7 percent of girls, and around 8 to 9 percent of boys said they got nine to 10 hours of sleep per night.

And, for the most part, sleep patterns for teenagers appeared to get worse with age -- surveys showed that by the time they reached 12th grade, a whopping 95 percent of high school seniors were not routinely meeting CDC sleep guidelines.

Girls tended to fare worse than boys, with girls being more prone to sleep five hours or fewer per night and less likely to get nine or more hours of sleep each night, the study found.

Race also appeared to figure into the equation: black teenagers were significantly more likely to get five or fewer hours of sleep per night than their white peers.

In each survey, 20 percent of black boys and girls were found to have daily sleep routines that included five or fewer hours of sleep. The same was true of 15 percent of Hispanic girls and about 12 percent of Hispanic boys.

According to Basch, early school start times are one major reason behind all those sleepless teens.

"More and more attention is being focused on the start times of schools, with the idea being that very early class schedules do not serve good sleep patterns," he said.

"That is certainly one of the problems," agreed Kelly Baron, an assistant professor of neurology and director of the Behavioral Sleep Medicine Program in the department of neurology with the Feinberg School of Medicine at Northwestern University in Chicago.

She called the data from the new report "alarming."

"While we're still trying to understand why this is happening, one of the reasons is clearly school start times," Baron said. "Having children wake up to start school at 6 or 7 a.m. is really at odds with their biology."

She explained that a person's sleep patterns "naturally change across our lifespan. And one of the most profound changes is that our natural 24-hour rhythm shifts as we enter puberty. Sure -- some of it's social, [and] kids just want to say up late and such. But the need to stay up later and sleep in later is also biological. So early school times set them up for a chronic sleep disadvantage."

So, can parents do anything to encourage more shut-eye for their kids?

"They can and should get involved," Baron said, "setting curfews, establishing sleep schedules, and limiting screen time in the bedroom. A healthy sleep environment at home is key."

The new study is published in the December issue of the CDC journal Preventing Chronic Disease.

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Lack of sleep in teens increases obesity

A study shows that teens who do not get enough sleep have an increased risk of becoming obese.

Teenagers who don't get enough sleep may wake up to worse consequences than nodding off during chemistry class. According to new research, risk of being obese by age 21 was 20 percent higher among 16-year-olds who got less than six hours of sleep a night, compared with their peers who slumbered more than eight hours. (The Centers for Disease Control and Prevention recommends nine to ten hours of sleep for teenagers.)

Researchers at the Mailman School of Public Health at Columbia University and the University of North Carolina Gillings School of Public Health are the first to examine the effect of sleeplessness on obesity in teenagers over time, providing the strongest evidence yet that lack of sleep raises risk for an elevated BMI. Results appear in Journal of Pediatrics.

Shakira F. Suglia, ScD, assistant professor of Epidemiology at the Mailman School, and colleagues analyzed health information from more than 10,000 American teens and young adults, ages 16 and 21, as part of the National Longitudinal Study of Adolescent Health. Information on height and weight and sleep was collected during home visits in 1995 and 2001.

Nearly one-fifth of the 16-year-olds reported getting less than six hours of sleep. This group was 20 percent more likely to be obese by age 21, compared to their peers who got more than eight hours of sleep. While lack of physical activity and time spent watching television contributed to obesity, they did not account for the relationship between sleeplessness and obesity.

"Lack of sleep in your teenage years can stack the deck against you for obesity later in life," says Suglia. "Once you're an obese adult, it is much harder to lose weight and keep it off. And the longer you are obese, the greater your risk for health problems like heart disease, diabetes, and cancer."

"The message for parents is to make sure their teenagers get more than eight hours a night," adds Suglia. "A good night's sleep does more than help them stay alert in school. It helps them grow into healthy adults."

Daytime sleepiness and fatigue are known to affect what and how people eat, by altering appetite and stimulating cravings. Energy levels may also play a role. For the sleep-deprived, ordering calorie-dense fast food is easier than preparing a nutritious meal. Information on what the teens ate was not captured in the surveys, although it could play a role. Future research may look whether, for example, soda consumption is a factor in sleeplessness and, in turn, obesity. (A 2013 study by Suglia found young children who drink soda are more likely to have behavioral problems.)

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Pediatricians urge later school start time

This article explains why pediatricians are urging for later school start times for older kids in middle and high schools.

U.S. high schools and middle schools should start classes later in the morning to allow kids some much-needed sleep, a leading group of pediatricians is urging.

Ideally, the American Academy of Pediatrics says, the first bell should ring at 8:30 a.m. or later -- which is the case at only 15 percent of U.S. high schools right now.

At the very least, classes should start no earlier than 8 a.m., said Dr. Judith Owens, the lead author of a new academy policy statement on school start times.

The recommendations, published in the academy's journal Pediatrics, are based on research showing that U.S. kids are sleep-deprived, which has consequences for their health, school performance and safety.

"This is an important issue," said Dr. Marcel Deray, a Florida sleep specialist who wasn't involved in the recommendations.

"I see a lot of teenagers who are tired and have problems in school because they have to get up so early," said Deray, who directs the Sleep Disorders Center at Miami Children's Hospital. "Some kids are getting up at 5 a.m., 6 a.m."

Many people think the answer is for kids to just get to bed earlier, Owens noted. But it's not that easy, she said, because biology has other plans.

Around puberty, the body's natural sleep-wake cycle shifts, and it's actually hard for teenagers to fall asleep earlier than 11 p.m.

"Teenagers' bodies release melatonin later than (adults') do," Deray explained, referring to a hormone the brain secretes in the evening to induce drowsiness.

"The other issue," Owens said, "is that teenagers' sleep needs are greater than many people think. They need nine to nine-and-a-half hours."

Yet, 43 percent of U.S. public high schools start classes before 8 a.m., according to the U.S. Department of Education. Middle schools, meanwhile, typically start classes at 8 a.m. -- with about 20 percent starting earlier than that.

"And that's the first bell," Owens said. "That's not even counting the commute time."

So in areas where kids take the school bus, the actual school day could begin before sunrise.

According to Owens, U.S. high schools started bumping up start times back in the 1950s and '60s, mainly to space out bus runs. Many school districts start high schools and middle schools first, then circle buses back to pick up elementary school kids.

One option would be to flip elementary and high school start times, but parents often oppose that -- since young children could be standing at bus stops in the early-morning dark, or have no one at home after school. Another option -- running more buses -- would be expensive.

Transportation is not the only obstacle, according to the National Sleep Foundation, which supports pushing back school start times. Some other arguments are that sports and extracurricular activities would end too late; teenagers would have no time for after-school jobs; and a later start could conflict with working parents' schedules.

Owens acknowledged the logistical challenges, and said parents and school staff sometimes oppose later start times. As an example, she said the Fairfax County, Va., school district has been debating the issue for years. Four options, including one with a 9:15 a.m. high school start, will be put to a vote this fall.

Some districts have found "creative solutions" to certain obstacles -- like having high school students switch from school buses to public ones, according to the academy.

Deray thinks tackling the practical challenges is worthwhile. He said studies have linked kids' sleep deprivation not only to poorer school performance, but also to higher rates of car accidents, obesity and depression.

In a recent study of eight U.S. high schools that delayed their start times, researchers found improvements in kids' grades, attendance and car crash rates.

Later school starts are just one way to help sleepy kids, however. Deray offered parents some tips.

"All electronic devices should be turned off an hour or two before bed," he said. "The blue light from them suppresses melatonin production."

He also advised avoiding physical and mental stimulation close to bedtime -- which means exercise and homework should be done earlier in the evening. And while teenagers love to sleep till noon on weekends, that will only further disturb their sleep/wake cycle. Deray said kids should get up by 9 a.m. on weekends and get plenty of morning sunlight.

He acknowledged, though, that all of that is easier said than done.

Owens agreed. "One of the issues is that kids are overscheduled," she said. "Don't give them so many things to do that they can't get to bed before midnight."

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Not getting enough sleep adds to health problems in teens

A study shows that teenagers increase their risk of developing health issues due to  getting too little sleep (6 hours or less). Electronics in the bedroom are blamed for getting too little sleep.

Many teens from lower- and middle-income homes get too little sleep, potentially adding to the problems of kids already at risk for health issues, new research finds.

The study of 250 high school students found they slept an average of six hours a night, far less than the recommended amount -- about nine hours.

Kids who skimp on sleep are more likely to report feeling hopeless, as well as smoke, drink alcohol and use marijuana, according to background information in the report, published online April 21 in Pediatrics.

"Many teenagers, especially blacks, do not get enough sleep, which may contribute to their risk for poor health," said lead researcher Karen Matthews, a professor of psychiatry at the University of Pittsburgh School of Medicine.

"Inadequate sleep can result in academic underachievement, health-damaging behaviors and negative mood," she said.

Matthews said sleep deprivation isn't confined to the poor. "Many kids who come from upper class families also do not get enough sleep, but our study focused on poorer children because of a lack of data available in those [upper class] students," she said.

The researchers wondered if the challenges of living in disadvantaged circumstances would affect sleep patterns. In their sample, 60 percent of the kids lived in single-family homes. Overall, the kids were heavier than national average, the researchers said.

Matthews isn't sure why these teens aren't sleeping enough. "However, factors that determine bedtime play a key role for sleep duration because of mandatory school start times," she said.

"Bedtimes can be quite late if students are using electronic devices late into the evening, and bright light exposure [from these devices] can keep them up," she said.

Late-night studying was not a factor in this sample, Matthews said.

Dr. Metee Comkornruecha, an adolescent medicine specialist at Miami Children's Hospital, said the study shows "what a lot of us are thinking -- that adolescents aren't getting enough sleep."

Kids are prone to a lot of distractions, he said. "Cell phones are used not only for texting but to look on the Internet and for various types of social media. That frequent stimulation can keep these kids up."

Comkornruecha recommended removing electronic distractions from the bedroom. "Take the phones, computer and TVs away from the bedroom. If they're there, kids are going to use them. But if the bedroom is a safe haven for sleeping, then that's what it is going to be used for," he said.

Among the students whose sleep patterns were monitored, 57 percent were black and 54 percent were girls. All came from low- to middle-class families.

Matthews said besides looking at kids from poorer families, they wanted to look at any differences by race because two studies of middle-aged adults suggested that blacks had worse sleep than whites. "Thus, we conducted our study at an integrated high school that had black and white students of similar economic backgrounds," Matthews added.

The researchers had the students complete questionnaires and keep a diary of the length and quality of their sleep. At night, the teens were hooked up to an electronic device that monitored their sleep.

On school nights, the teens slept about six hours, and on the weekend, about seven hours. Matthews' team found that blacks and males slept less than other kids, and their sleep was more fragmented. Girls reported poorer quality of sleep and said they were often tired during the day.

The researchers previously reported that insufficient sleep is linked to higher blood pressure and insulin resistance, a risk factor for diabetes.

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Study: Later school start times are beneficial for adolescents

A study shows that later school start times result in improved sleep quality and a better overall mood in adolescents.

Julie Boergers, Ph.D., a psychologist and sleep expert from the Bradley Hasbro Children's Research Center, recently led a study linking later school start times to improved sleep and mood in teens. The article, titled "Later School Start Time is Associated with Improved Sleep and Daytime Functioning in Adolescents," appears in the current issue of the Journal of Developmental & Behavioral Pediatrics.

"Sleep deprivation is epidemic amongadolescents, with potentially serious impacts on mental and physical health, safety and learning. Early high school start times contribute to this problem," said Boergers. "Most teenagers undergo a biological shift to a later sleep-wake cycle, which can make early school start times particularly challenging. In this study, we looked at whether a relatively modest, temporary delay in school start time would change students' sleep patterns, sleepiness, mood and caffeine use."

Boergers' team administered the School Sleep Habits Survey to boarding students attending an independent high school both before and after their school start time was experimentally delayed from 8 to 8:25 a.m. during the winter term.

The delay in school start time was associated with a significant (29 minute) increase in sleep duration on school nights, with the percentage of students receiving eight or more hours of sleep on a school night jumping from 18 to 44 percent. The research found that younger students and those sleeping less at the start of the study were most likely to benefit from the schedule change. And once the earlier start time was reinstituted during the spring term, teens reverted back to their original sleep levels.

Daytime sleepiness, depressed mood and caffeine use were all significantly reduced after the delay in school start time. The later school start time had no effect on the number of hours students spent doing homework, playing sports or engaging in extracurricular activities.

Boergers, who is also co-director of the Pediatric Sleep Disorders Clinic at Hasbro Children's Hospital, said that these findings have important implications for public policy. "The results of this study add to a growing body of research demonstrating important health benefits of later school start times for adolescents," she said. "If we more closely align school schedules with adolescents' circadian rhythms and sleepneeds, we will have students who are more alert, happier, better prepared to learn, and aren't dependent on caffeine and energy drinks just to stay awake in class."

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Sleep loss can raise teenager's blood pressure

Sleep loss in teenagers has many negative health outcomes, such as daytime sleepiness and raising their blood pressure, which can lead to serious health conditions later in life.

Beyond making teens sleepy during the day, staying up late may be raising their blood pressure, setting them up for later heart troubles, say Chinese researchers.

"Sleep is an essential part of everyone's life. However, with continuous advancement of technology, the portion of sleep in each day is diminishing," the study's lead author Chun-Ting Au told Reuters Health in an email.

Au is a research associate in the Department of Pediatrics at the Faculty of Medicine of the Chinese University of Hong Kong.

He and his team wanted to examine the relationship between sleep and blood pressure in teens without other potential causes of high blood pressure, such as obesity or sleep apnea.

"Scientifically, as the association between sleep duration and blood pressure was still uncertain, we decided to conduct this study to examine the association in a more precise way," Au said.

The researchers invited adolescents who had participated in a previous study on obstructive sleep apnea. All participants in the new study were healthy and not overweight or obese for their ages, and none had sleep apnea or recent surgery involving the airways.

A total of 143 kids between the ages of 10 and 18 completed the study. The kids filled out sleep diaries for seven days before they entered a sleep lab for 24-hour sleep studies, where they were monitored for blood pressure, sleep duration and the quality of their sleep.

In general, the children who had less total sleep during the week had slightly higher blood pressure measurements. On average, each hour of nightly lost sleep was associated with an increase of 2 mm Hg in systolic blood pressure (the top number) and 1 mm Hg in diastolic blood pressure.

The study did not prove that short sleep duration would cause high blood pressure in adolescents. Some other cause could be behind both the higher blood pressure readings and reduced sleep times.

The researchers point out that previous studies have found that kids with short sleep times had higher levels of the stress hormone cortisol in the morning, and that sleep deprivation may blunt the ability of blood vessels to respond to changes in pressure.

In the current study, researchers also found that kids who got the least amount of sleep based on their sleep diaries generally had later bedtimes and woke up earlier every day. But during the 24-hour sleep study, those kids fell asleep sooner and had longer total sleep times than the rest of the kids.

This change in sleep patterns might signal a rebound from sleep deprivation in the preceding week and suggests that kids might be able to make up for some lost sleep, Au's team writes in the journal Pediatrics.

"Our results found that blood pressure was sensitive to changes in sleep pattern, implicating that having longer sleep may have beneficial effects on blood pressure and thus cardiovascular health," Au said.

"On the other hand, although blood pressure was more closely associated with the sleep time on the night before, the carryover effect of the ‘sleep debt' accumulated over the past few days remained significant," he said.

"This suggests that occasional adequate sleep, as what we commonly do during weekends, may improve the situation a little bit, but does not completely reverse the detrimental effects of long-term sleep deprivation on blood pressure," Au said.

Dr. Judith Owens, director of Sleep Medicine at the Children's National Medical Center in Washington, DC, said there's not much published research in this area.

"As the authors point out, a lot of what's been done previously was confounded by this issue of obesity and obstructive sleep apnea. I think this was a very important and innovative step to eliminate those confounding variables, and look at this issue in otherwise healthy adolescents," she told Reuters Health.

Owens, a professor of Pediatrics at George Washington University School of Medicine and Health Sciences, was not involved in the new study.

She said this is an issue that affects all teenagers, not just kids who have sleep problems.

"This is something that goes on for at least 9 months of the year, for years, for the average adolescent, so the implication that this may have measurable cardiovascular effects is so important," Owens said.

Owens also said she hopes reports like this lead to long-term studies following sleep-deprived teens into their adult years.

"If we can see these short term kinds of effects, maybe we'll see more funding to do these very expensive studies where we're measuring these same kinds of issues in adults who were adolescents undergoing this sleep deprivation," she said.

Owens also told Reuters Health that disruptions in circadian rhythms might also contribute to cardiovascular risk.

Adolescents are often sleep deprived during the school year because their circadian rhythms don't match up with school schedules and they often can't fall asleep early enough to meet their sleep needs.

Au says parents can help their kids get the sleep they need.

"Be consistent and perseverant," he wrote in an email. "There are several techniques (e.g. developing a nightly bedtime routine) that can help children establish a regular sleep pattern. You may easily obtain a list of them from the Internet. No matter what technique you use, consistency and perseverance is the key to success."

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Sleep deprivation results in poor dietary choices in teenagers

Teenagers who get less sleep make poor dietary choices as opposed to teenagers who get enough sleep.

Well-rested teenagers tend to make more healthful food choices than their sleep-deprived peers, according to a study led by Lauren Hale, PhD, Associate Professor of Preventive Medicine at Stony Brook University School of Medicine. The finding, presented at SLEEP 2013, the annual meeting of the Associated Professional Sleep Societies, may be key to understanding the link between sleep and obesity.

"Not only do sleepy teens on average eat more food that's bad for them, they also eat less food that is good for them," said Dr. Hale, speaking about the study results. "While we already know that sleep duration is associated with a range of health consequences, this study speaks to some of the mechanisms, i.e., nutrition and decision making, through which health outcomes are affected."

The study, which was supported by the National Institute of Diabetes and Digestive and Kidney Diseases, examined the association between sleep duration and food choices in a national representative sample of 13,284 teenagers in the second wave of the National Longitudinal Study of Adolescent Health. The data were collected in 1996 when the interview subjects had a mean age of 16 years.

The authors found that those teens who reported sleeping fewer than seven hours per night -- 18 percent of respondents -- were more likely to consume fast food two or more times per week and less likely to eat healthful food such as fruits and vegetables. The results took into account factors such as age, gender, race and ethnicity, socioeconomic status, physical activity and family structure, and found that short sleep duration had an independent effect on both healthy and unhealthy food choices.

The respondents fell into one of three categories: short sleepers, who received fewer than seven hours per night; mid-range sleepers, who had seven to eight hours per night; and recommended sleepers, who received more than eight hours per night. The American Academy of Pediatrics currently recommends that adolescents get between nine and 10 hours of sleep per night.

"We are interested in the association between sleep duration and food choices in teenagers because adolescence is a critical developmental period between childhood and adulthood," said the first author of the study, Allison Kruger, MPH, a community health worker at Stony Brook University Hospital. "Teenagers have a fair amount of control over their food and sleep, and the habits they form in adolescence can strongly impact their habits as adults."

The research team -- which included co-authors Eric N. Reither, PhD, Utah State University; Patrick Krueger, PhD, University of Colorado at Denver; and Paul E. Peppard, PhD, University of Wisconsin-Madison -- concluded that addressing sleep deficiency may be a novel and effective way to improve obesity prevention and health promotion interventions.

Dr. Hale said that one of the next steps in the research will be to explore whether the association between sleep duration and food choices is causal.

"If we determine that there is a causal link between chronic sleep and poor dietary choices, then we need to start thinking about how to more actively incorporate sleep hygiene education into obesity prevention and health promotion interventions," she said.

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