By Shereen Jegtvig
NEW YORK (Reuters Health) - 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."
SOURCE: http://bit.ly/J2FeuY Pediatrics, online December 16, 2013.