Sunday, March 26, 2006

Sleep Schedules in Adolescents

I am glad to see that there is more and more interest in and awareness of sleep research. Just watch Sanjay Gupta on CNN or listen to the recent segment on Weekend America on NPR.

At the same time, I am often alarmed at the levels of ignorance still rampant in the general population, and even more the negative social connotations of sleep as an indicator of laziness.

Nothing pains me more than when I see educators (in comments) revealing such biases in regards to their student in the adolescent years. Why do teachers think that their charges are lazy, irresponsible bums, and persist in such belief even when confronted with clear scientific data demonstrating that sleep phase in adolescents is markedly delayed in comparison to younger and older people?

The shift in sleep-phase of adolescents is one of the best documented and most studied phenomena in human chronobiology. If you dig through my ClockNews category, you'll see that almost every issue has something about adolescent sleep patterns. My first and still most popular post here addresses this phenomenon in some detail (as well as some advice), especially this sweet paper that came out a couple of years ago (follow the references within or search MedLine, Web of Science or Google Scholar for more information).
In short, presumably under the influence of the sudden surge of sex steroid hormones (and my own research gently touches on this), the circadian clock phase-advances in teen years. It persists in this state until one is almost 30 years old. After that, it settles into its adult pattern. Of course, we are talking about human populations - you can surely give me an anecdote about someone who does not follow this pattern. That's fine. Of course there are exceptions, as there is vast genetic (and thus phenotypic) variation in human populations. This does not in any way diminish the findings of population studies.

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.

Along a different continuum, one can be very rigid (usually the extreme larks find it really difficult to adjust to work schedules that do not fit their clocks), or quite flexible (people who find it easy to work night-shifts or rotating shifts and tend to remain in such jobs long after their colleagues with less flexible clocks have quit).

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 important thing to remember is that chronotypes are not social constructs (although work-hours and school-hours are). No amount of bribing or threatening can make an adolescent fall asleep early. Don't blame video games or TV. Even if you take all of these away (and you should that late at night, and replace them with books) and switch off the lights, the poor teen will toss and turn and not fall asleep until midnight or later, thus getting only about 4-6 hours of sleep until it is time to get up and go to school again.

More and more school districts around the country, especially in more enlightened and progressive areas are heeding the science and making a rational decision to follow the science and adjust the school-start times accordingly. Instead of forcing teenagers to wake up at their biological midnight (circa 6am) to go to school, where invariably they sleep through the first two morning classes, more and more schools are adopting the reverse busing schedule: elementary schools first (around 7:50am), middle schools next (around 8:20am) and high schools last (around 8:50am). I hope all schools around the country eventually adopt this schedule and quit torturing the teens and then blaming the teens for sleeping in class and making bad grades.

No matter how much you may wish to think that everything in human behavior originates in culture, biology will trump you every now and then, and then you should better pay attention, especially if the life, health, happiness and educational quality of other people depends on your decisions.

(See more here)


Anonymous Anonymous said...

Finally, someone understands! Getting up at 6 is a pain!

-Russ, 16

11:58 PM  
Anonymous Anonymous said...

I'm still skeptical.. I personlly feel that environmental inputs are still more dominant than biological inputs. For example, elementary students have much more time in physical play (PE and multiple recesses), middle school students lack recess and have wonky PE schedules, high school students lack recess all together and usually only participate in PE a total of 1 year out of 4. Sports complicates the situation at middle and high school, but it's not required of all. In passing I hear people commonly associate their tiredness and bedtime/wake time with their excersize. People don't often draw rational conclusions or make proper correlations, but it at least needs to be studied.

The 5 or so studies I have read seem to gloss over these environmental factors that people often anectodally cite and focus mostly on the TV and 'bedtime' argument. The TV and bedtime factor has been shown to be negligble in an number of studies. Nutrition is not looked at in the least bit, yet there is a dramatic shift in eating habits and foods between elementary and high school. Skipping breakfast, for example, might have an effect on metabolism. The change in types of foods from more wholesome to more carb-based foods could change that equation.

Whether anything I've conjectured has an impact on the circadian cycle I'm not sure. It might be biological. However, I haven't seen a study that seeks to control variables I feel are important. If anyone knows of some studies that seek to address any of these inputs, I'd love a nudge in the right direction. Until then, I can't really support changing schedules.

To close, I list below a few 'issues' uncovered in my district when we attempted to change schedules. I'm not claiming these can't be worked around. These just surfaced and were noted.
1. Elementary first means younger kids out in the dark in the morning (safety).
2. Elementary last changes parents' schedules since they usually time their commute on prepping the little ones.
3. Higher costs for after school care for elementary students (they start earlier and end earlier)
4. High School Sports schedules might be affected, especially with other districts. This includes practice time in the winter before sundown.
5. Assuming a constant amount (time) that a high school student chooses to spend on activities, socialization, eating, and homework, this could push the bedtime even later.
6. Bus timing concerns were raised, but I can't recall the specific argument. My recollection suggested pushing buses later incurred higher costs because commute traffic was worse in the evening than the morning for my district.

2:12 PM  
Anonymous Anonymous said...

I'm in the UK and almost all state (public) schools start at 9.00 give or take ten minutes. It may be the owl in me talking - but it seems unecessarily bizarre to start any earlier. Finish times average at 3.30 and all schools have a morning recess and sometimes an afternoon break (recess).

I still think a 9.00 start is too early for teenagers, but I can see that a later one could cause problems with the commute for working parents.

12:01 PM  
Blogger cathyf said...

I would be willing to argue that perhaps the reason why adolescents seem to do so much better with later school starts is competition.

Scenario 1: Kid wakes up at 5:30 and gets to high school at 7:30am. Sleeps in chair for the first 2 classes. Gets dismissed at 2pm. Is at the minimum-wage job by 2:30. Arrives home from job at 10:30, starts homework. Finishes homework at midnight, watches TV, reads until 1am.

Scenario 2: Kid wakes up at 7:30 and gets to high school at 9:30am. Stays awake the whole day until dismissal at 4pm. Gets to minimum-wage job by 4:30. Arrives home from job at 10:30, starts homework. Finishes homework at midnight, watches TV, reads until 1am.

For the minimum-wage job, substitute sports, or band practice or whatever. Even in the "it's not biology it's culture and teenagers are just lazy" world you are making a choice -- do the kids sacrifice their academic classes, or do the academics come first before stupid McJobs, or sports, or other extracurriculars?

If I were going to set up a high school schedule, school would run from 10:30-5:00, and all extracurriculars and sports practices would be BEFORE school, or after dinner. Reserve the prime brain-functioning times for academics, and then any kid who really wants to do the other stuff can drag his butt out of bed and do it before school.

3:19 PM  

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