Teenagers tend to stay up later at night and sleep in on the weekends. However, a new study published today in Hypertension shows that erratic sleep patterns may affect heart health in the future by raising blood pressure in teens with more abdominal fat.

303 central Pennsylvanian teenagers (mean age 16.2 years; 47.5% female; 21.5% Black or Hispanic) who had previously participated as children in the Penn State Child Cohort study were re-examined for changes in sleep, visceral fat, and blood pressure.

A sleep monitoring device that looked like a wristwatch was worn at home for a period of seven nights, as well as during the one night that was spent at the sleep lab. With this device, researchers kept track of how long teens slept and how much their sleep changed from night to night.

They also kept track of how often teens woke up in the middle of the night (to capture their sleep patterns over time). For a typical teen during the school week, a sleep midpoint of 2 a.m. or later is considered late, and changes of 45 minutes or more from one night to the next are considered very irregular.

During the visit to the sleep lab, the visceral abdominal fat—the deep belly fat that envelops the stomach, liver, and intestines—was assessed using a dual-energy X-ray absorptiometry (DEXA) scan. Heart health is more at risk from visceral fat than from subcutaneous fat. During the visit to the sleep lab, sitting blood pressure was also checked three times at 5-minute intervals, with the latest two values averaged.

The findings:

• Overall, the participants slept like teenagers do. They went to bed later than they did in grade school, and they slept longer on weekends and school breaks than they did during the week.
• Each unit increase in visceral abdominal fat was associated with a 7 mm Hg higher systolic (top number) blood pressure and a 3 mm Hg higher diastolic (bottom number) blood pressure among the adolescents who slept irregularly by 45 minutes or more during the school week and were studied during the school year.
• In contrast, among youths whose sleep changed less than 45 minutes over the school week, there was no relationship between visceral belly fat and high blood pressure.
• Each unit increase in visceral abdomen fat was associated with a 5 mm Hg rise in systolic blood pressure and a 2 mm Hg rise in diastolic blood pressure in individuals who slept later on weekdays (with a sleep midpoint of 2 a.m. or later). Visceral abdominal fat did not raise blood pressure in early sleepers.
• The link between visceral abdominal fat and blood pressure didn’t change much for the teens who took part in the study during a school break, whether they slept regularly or not.
• Each unit increase in visceral abdominal fat was linked to a 3 mm Hg rise in diastolic blood pressure in teens who said they were “evening people.” However, visceral abdominal fat had no effect on blood pressure in teens who said they were “morning people.”

According to first author Natasha Morales-Ghinaglia, the findings of the study indicate “that keeping a regular sleep pattern may protect adolescents from the cardiovascular consequences of obesity.”

According to Morales-Ghinaglia, it is normal for teenagers to have a natural inclination to sleep later than they did in their childhood years. Previous studies have demonstrated that this is a typical developmental pattern that conflicts with some aspects of the adolescent lifestyle, especially school and extracurricular schedules.

“Teens are not wrong in following their normal inclinations to sleep later than in their childhood years,” adds the first author.

“Rather, it’s a normal developmental pattern that previous studies have shown to be at odds with certain aspects of teen lifestyle ― primarily school and extracurricular activity schedules.”

Experts on sleep have emphasized that the early start times of middle and high schools make it difficult for teenagers to acquire adequate, consistent sleep. Morales-Ghinaglia stresses the importance of being in tune with one’s body, both for parents and adolescents.

“It’s important to educate teens on how important it is to have regular sleep. They don’t need an early bedtime like younger children, but it’s important to get more regular sleep for the benefit of their heart and mental health.”

There are various limitations to the research. The findings cannot show a cause-and-effect relationship between sleep patterns and blood pressure since it was not a controlled experiment where researchers could compare groups based on variables like sleep circumstances or patterns, and because the subjects were only examined once.

There was just one night of sleep testing in a sleep lab and seven nights of monitoring at home; this may not be as trustworthy as measures taken over the course of more than one night in a sleep lab and 14 nights or more of home monitoring, with the latter ideally including several weekend nights.

As blood pressure was only measured in the lab, it may not accurately represent typical blood pressure values, such as those recorded over the course of a 24-hour period with repeated readings.

Senior author Julio Fernandez-Mendoza suggests that pediatricians closely monitor young people who are experiencing weight gain or are already overweight and examine their sleep patterns. According to him, a more regular sleep schedule may aid in weight loss and improve long-term heart health.

Image Credit: Ute Grabowsky/Photothek via Getty Images