Bora Zivkovic compiles some information on how kids circadian rhythms change during adolescence, and advocates for later school starting hours.
He points out the interesting concept of chronotypes:
Everyone, from little children, through teens and young adults to elderly, belongs to one of the ‘chronotypes’. You can be a more or less extreme lark (phase-advanced, tend to wake up and fall asleep early), a more or less extreme owl (phase-delayed, tend to wake up and fall asleep late). You can be something in between – some kind of “median” (I don’t want to call this normal, because the whole spectrum is normal) chronotype.
And how your chronotype gets phase-delayed at puberty:
No matter where you are on these continua, once you hit puberty your clock will phase-delay. If you were an owl to begin with, you will become a more extreme owl for about a dozen years. If you are an extreme lark, you’ll be a less extreme lark. In the late 20s, your clock will gradually go back to your baseline chronotype and retain it for the rest of your life.
The study was presented at the annual Pediatric Academic Societies meeting under the title Is Sleep Related to Obesity in Young Adolescents?. Interestingly enough, there was less of a correlation for girls.
However, in girls, sleep duration was not related to any of the weight-related variables with the exception of less sleep on weekends being related to BMI. – Lytle, Pasch and Farbaksh, 2010.
The USDA has a nice page that touches on the research that’s looking for specific links between sleep deprivation and weight. Their take is that kids don’t get out enough because increased opportunities for indoor entertainment don’t require much activity and disrupt sleep cycles. They suggest that fat cells themselves may respond to changing circadian rhythms.
Abnormal sleep/wake patterns may change circadian clocks that normally allow cells to anticipate variations in the outside environment, such as changing levels of nutrients (glucose, fatty acids and triglycerides) and hormones such as insulin. – Flores, 2007.
I remain fascinated by the Brazilian study that found that kids living in homes without electricity did not have the same sleep deprivation issues as those with electricity. I thought of it again recently when I ran across the term “nature-deficit disorder” in Oak Hill Montessori school’s newsletter.
Unstructured nature time is so important because children live through their senses. When they are right there in the forest, they are getting a primary multi-sensory experience of nature as opposed to the secondary, often distorted, dual-sensory view presented by TV. – Daniels, 2009 (p. 4)
The idea of nature-deficit disorder comes from the book “Last Child in the Woods” by Richard Louv. Written in 2005 and updated in 2008 with a bunch of practical things you can do to change things, Louv’s book advocates for more time in nature because, “a growing body of research links our mental, physical, and spiritual health directly to our association with nature.” Not only does it affect our individual health, but directly experiencing nature also helps increase environmental awareness (which ties into the Montessori peace curriculum). Louv argues that children have a fundamental right to walk in the woods:
Science sheds light on the measurable consequences of introducing children to nature; studies pointing to health and cognition benefits are immediate and concrete. We also need to articulate the underlying “first principle”—one that emerges not only from what science can prove, but also from what it cannot fully reveal; one that resists codification because it is so elemental: a meaningful connection to the natural world is fundamental to our survival and spirit, as individuals and as a species. Louv (2009)
I can’t say I disagree very much with this diagnosis. My adolescents are too often opting for technology rather than being outside, especially if it’s in nature. This is one reason my students are building the nature trail. The trail has been coming along slowly though, but the seasons are changing and we’ll spend more time outside in the warmer weather. The timing is also nice because we’ve just finished covering simple machines in physics. There are logs and junk to be moved and saplings to be cleared.
Note: Louv has a long list of links to print and broadcast articles on the whole “nature-deficit disorder” concept.
I’m often surprised by how late my student get to sleep. It can range from 9 pm to past midnight, and I’d love to be able to recommend to parents that their kids should go to sleep earlier. However, the research on sleep patterns among adolescents shows the issue is a bit more complex.
First off, adolescents should get about 9 hours and 15 minutes of sleep per night according to Bill Dement (1999) who guided a lot of the foundational studies on sleep patterns. Not getting that much sleep, especially on recurring basis, results in sleep deprivation, which is well known to have a negative effect on school performance (Mayo Clinic staff, 2009). And a lot of adolescents are getting less than 9 hours.
But just setting earlier bedtimes may not work. Late in puberty adolescents’ biological clocks change, creating a window in the evening when it is difficult to get to sleep:
“[M]any adolescents … actually feel great at night and, for many of them, that makes it harder for them to even consider trying to go to bed earlier. So they’ll say goodnight to Mom and Dad and they’ll go into their rooms and read or play video games or talk on the phone. And they’re perfectly content and happy doing that, because they’re also at a phase where it’s easy for them to become aroused and stimulated by these activities. So it really does turn into a Catch–22. When people just say, “Well, all they have to do is go to bed earlier,” well, they really can’t go to sleep earlier necessarily.” – Mary Carskadon in Frontline (2002).
However, Mary Carskadon‘s research (and others) has shown that despite the changes in the biological clock that occur during adolescence, children still need the same total amount of sleep, even if they’re not getting it.
reduced habitual sleep time reported by adolescents may be related more to environmental factors (social, academic, and peer pressure) than to declining “need” for sleep. – Carskadon et. al. (1980)
So the fact that adolescents are not getting enough sleep is likely because of how society has changed. An interesting Brazilian study found that children living in homes without electrical lighting had significantly earlier sleep times than those with electricity (Peixoto et. al., 2009). Another study found that sleep deprivation was related to the amount of multitasking students did at night.
Adjust the lighting. As bedtime approaches, dim the lights. Turn the lights off during sleep. In the morning, expose your teen to bright light. These simple cues can help signal when it’s time to sleep and when it’s time to wake up.
Stick to a schedule. Tough as it may be, encourage your teen to go to bed and get up at the same time every day — even on weekends. Prioritize extracurricular activities and curb late-night social time as needed. If your teen has a job, limit working hours to no more than 16 to 20 hours a week.
Nix long naps. If your teen is drowsy during the day, a 30-minute nap after school may be refreshing. But too much daytime shut-eye may only make it harder to fall asleep at night.
Curb the caffeine. A jolt of caffeine may help your teen stay awake during class, but the effects are fleeting. And too much caffeine can interfere with a good night’s sleep.
Keep it calm. Encourage your teen to wind down at night with a warm shower, a book or other relaxing activities — and avoid vigorous exercise, loud music, video games, text messaging, Web surfing and other stimulating activities shortly before bedtime. Take the TV out of your teen’s room, or keep it off at night. The same goes for your teen’s cell phone and computer.
Finally, I’m still thinking about what this means for students taking naps during personal world time. I’m not usually opposed to the occasional short nap, but just how much does this help?
