Importance of when adolescents sleep to obesity and cardiometabolic health
September 16, 2019
Science Daily/Massachusetts General Hospital
A new study led by researchers at Massachusetts General Hospital for Children (MGHfC) and Harvard Medical School has found that adolescent sleep timing preferences and patterns should be considered risk factors for obesity and cardiometabolic health, and that the effects are greater in girls than in boys.
Poor quality and short duration of sleep are known to increase obesity and cardiometabolic risk among children. What's rarely been studied, however, is how sleep timing and teens' own preferences for when to sleep and engage in other activities can influence their risk of obesity and poor cardiometabolic health.
"Beyond quantity and quality, timing is a vital component of sleep because it determines if an individual's circadian clock -- the internal sleep/wake schedule -- is synchronized with the rhythms of their daily activities," says Elsie Taveras, MD, MPH, division chief, General Academic Pediatrics, MGHfC, and senior investigator of a new study published in JAMA Pediatrics. "This is particularly important to adolescents whose evening preferences and academic demands often result in irregular sleep schedules that may cause circadian misalignment. Our research found that 'night owls,' teenagers who prefer to go to bed late but have to get up early for school, had higher waist circumference and greater abdominal fat deposition (adiposity) than the 'morning larks,' those who prefer to go to bed early and get up early to begin their day."
The researchers emphasized the need for consistent sleep-wake patterns throughout the week, including on weekends, to reduce the risk of obesity and promote cardiometabolic health.
The research team studied 804 children who were part of Project Viva, a groundbreaking cohort study begun 20 years ago by researchers at the Harvard Pilgrim Health Care Institute that followed Boston-area mothers and children to characterize early-life factors that influence long-term health. Scientists examined chronotypes (evening versus morning preferences) and "social jet lag" (differences in sleep timing between school and free days) in children 12 to 17 years of age. Evening chronotypes and greater social jet lag were associated with higher adiposity.
"Large variability in sleep patterns across the week can disrupt normal physiology, resulting in obesity and cardiometabolic risk," explains lead author Elizabeth Cespedes Feliciano, ScD, ScM, formerly at the Harvard Chan School of Public Health and now research scientist in the Kaiser Permanente Northern California Division of Research.
"Our study supports the importance of biological clocks in influencing obesity risk." Stronger associations with adiposity were observed for girls versus boys. "While the reasons for that difference are not fully understood, they may include biological and sociocultural influences," says Feliciano.
Helping teenagers address the effects of chronotypes and social jet lag calls for family, clinical and community-based initiatives, according to the investigators. "Families should encourage consistency in their children's sleep schedules and their bed and wake times as well as improvements in their sleep hygiene by limiting electronic media and caffeine use in the evening," says Feliciano.
Schools can also play an important role by enacting polices that delay morning start times and by making it easier for students to devote time during the school day to academic or athletic activities that are spilling more and more into the late night, says Taveras. From a clinical standpoint, she adds, physicians should start to include chronotypes and social jet lag in their preventive counseling. "Physicians should be aware of the importance of encouraging adolescents to follow consistent sleep schedules on weekdays and weekends," she says. "Adolescent girls and 'owls' may especially benefit from keeping consistent sleep schedules."
https://www.sciencedaily.com/releases/2019/09/190916110604.htm
Poor grades tied to class times that don't match our biological clocks
Schedules of night owls, morning larks and daytime finches may predict their educational outcomes.
March 29, 2018
Science Daily/University of California - Berkeley
It may be time to tailor students' class schedules to their natural biological rhythms. A study shows that students whose circadian rhythms were out of sync with their class schedules received lower grades due to 'social jet lag,' a condition in which peak alertness times are at odds with work, school or other demands.
Researchers tracked the personal daily online activity profiles of nearly 15,000 college students as they logged into campus servers.
After sorting the students into "night owls," "daytime finches" and "morning larks" -- based on their activities on days they were not in class -- researchers compared their class times to their academic outcomes.
Their findings, published today in the journal Scientific Reports, show that students whose circadian rhythms were out of sync with their class schedules -- say, night owls taking early morning courses -- received lower grades due to "social jet lag," a condition in which peak alertness times are at odds with work, school or other demands.
"We found that the majority of students were being jet-lagged by their class times, which correlated very strongly with decreased academic performance," said study co-lead author Benjamin Smarr, a postdoctoral fellow who studies circadian rhythm disruptions in the lab of UC Berkeley psychology professor Lance Kriegsfeld.
In addition to learning deficits, social jet lag has been tied to obesity and excessive alcohol and tobacco use.
On a positive note: "Our research indicates that if a student can structure a consistent schedule in which class days resemble non-class days, they are more likely to achieve academic success," said study co-lead author Aaron Schirmer, an associate professor of biology at Northeastern Illinois University.
While students of all categories suffered from class-induced jet lag, the study found that night owls were especially vulnerable, many appearing so chronically jet-lagged that they were unable to perform optimally at any time of day. But it's not as simple as students just staying up too late, Smarr said
"Because owls are later and classes tend to be earlier, this mismatch hits owls the hardest, but we see larks and finches taking later classes and also suffering from the mismatch," said Smarr. "Different people really do have biologically diverse timing, so there isn't a one-time-fits-all solution for education."
In what is thought to be the largest-ever survey of social jet lag using real-world data, Smarr and Schirmer analyzed the online activity of 14,894 Northeastern Illinois University students as they logged in and out of the campus's learning management system over two years.
To separate the owls from the larks from the finches, and gain a more accurate alertness profile, the researchers tracked students' activity levels on days that they did not attend a class.
Next, they looked at how larks, finches and owls had scheduled their classes during four semesters from 2014 to 2016 and found that about 40 percent were mostly biologically in sync with their class times. As a result, they performed better in class and enjoyed higher GPAs.
However, 50 percent of the students were taking classes before they were fully alert, and another 10 percent had already peaked by the time their classes started.
Previous studies have found that older people tend to be active earlier while young adults shift to a later sleep-wake cycle during puberty. Overall, men stay up later than women, and circadian rhythms shift with the seasons based on natural light.
Finding these patterns reflected in students' login data spurred researchers to investigate whether digital records might also reflect the biological rhythms underlying people's behavior.
The results suggest that "rather than admonish late students to go to bed earlier, in conflict with their biological rhythms, we should work to individualize education so that learning and classes are structured to take advantage of knowing what time of day a given student will be most capable of learning," Smarr said.
https://www.sciencedaily.com/releases/2018/03/180329190847.htm
Lack of sleep could cause mood disorders in teens
December 6, 2017
Science Daily/American College of Neuropsychopharmacology
Chronic sleep deprivation -- which can involve staying up late, and waking up early for work or school -- has become a way of life for both kids and adults, especially with the increasing use of phones and tablets late into the night. But this social jet lag poses some serious health and mental health risks: new research finds that for teenagers, even a short period of sleep restriction could, over the long-term, raise their risk for depression and addiction.
University of Pittsburgh's Peter Franzen and Erika Forbes invited 35 participants, aged 11.5-15 years, into a sleep lab for two nights. Half the participants slept for 10 hours, while the other half slept only four hours. A week later, they came back to the lab for another two nights and adopted the opposite sleep schedule from their initial visit.
Each time they visited the lab, the participants underwent brain scans while playing a game that involved receiving monetary rewards of $10 and $1. At the end of each visit, the teens answered questions that measured their emotional functioning, as well as depression symptoms.
The researchers found that sleep deprivation affected the putamen, an area of the brain that plays a role in goal-based movements and learning from rewards. When participants were sleep-deprived and the reward in the game they played was larger, the putamen was less responsive. In the rested condition, the brain region didn't show any difference between high- and low-reward conditions.
Franzen and Forbes also found connections between sleep restriction and mood: after a night of restricted sleep, the participants who experienced less activation in the putamen also reported more symptoms of depression. This is consistent with findings, from a large literature of studies on depression and reward circuitry, that depression is characterized by less activity in the brain's reward system.
The results suggest that sleep deprivation in the tween and teen years may interfere with how the brain processes rewards, which could disrupt mood and put a person at risk of depression, as well as risk-taking behavior and addiction.
https://www.sciencedaily.com/releases/2017/12/171206090624.htm