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10/25/2006
Too Much Growth, Too Little Sleep
After posting this column, I’m off to New York with my wife’s
Wednesday matinee theater group to see the play “Drowsy
Chaperone” on Broadway. If the play lives up to the reviews, it
should be quite lively and I shouldn’t be at all drowsy during the
performance - a segue to more on sleep, a topic we covered a
couple of weeks ago. In that column we discussed how we
humans and fruit flies share very similar sleep characteristics.
Last week I came across an article in the September 22 Science
by Indrani Ganguly-Fitzgerald (The Neurosciences Institute in
San Diego), Jeff Donlea and Paul Shaw (Washington University
in St. Louis). The article was titled “Waking Experience Affects
Sleep Need in Drosophila”. They’ve found that Drosophila, the
fruit fly, sleeps more soundly if it has an active social life. Who
knew that a fruit fly has a social life?
I may get back to the fruit fly later but a Reuters dispatch dated
October 19 on the AOL News site seemed more important in
light of the current obesity crisis. The dispatch, headlined
“Obesity May Be Related to Lack of Sleep”, concerned an article
published by Bristol University’s Shahrad Taheri in the
November issue of Archives of Disease in Childhood. Taheri
reviews work linking a lack of sufficient sleep in children and
adolescents with obesity. My first thought, and my wife’s also,
was that a sleep-deprived individual would be on the thin side.
However, a visit to the University of Bristol Web site revealed a
wealth of information and references dating back to 1992 relating
obesity and sleep deprivation.
In 1992, E. Locard and a group of French workers at Groupe de
Recherche en Education Pour La Sante in Lyon published a
study on 5-year-old French children in the October 1992 Journal
of Obesity Related Metabolic Disorders. The researchers looked
at various environmental factors including family structure and
economic status, weight at birth, lifestyle factors including TV
viewing, sleep patterns, snacking, etc. They concluded that the
environmental factors contributing to childhood obesity were a
mother’s southern European origin (1.9), snacks (1.3), too much
TV watching (2.1) and too little sleep (4.9). The numbers in
parentheses are relative risks. I don’t know how these risk
factors were calculated but it seems that lack of sleep is more
than twice as likely a cause of obesity as any of the other factors.
Of course, watching TV takes away time for a child to exercise
but why should less sleep be a cause of obesity? Hormones may
be the answer. In work published in the December 2004 issue of
the open-access medical journal Public Library of Science
Medicine, Taheri, Ling Lin and Emmanuel Mignot (all then at
Stanford University) collaborated with Diane Austin and Terry
Young of the University of Wisconsin. The article was titled
“Short Sleep Duration Is Associated with Reduced Leptin,
Elevated Ghrelin, and Increased Body Mass Index”.
Believe it or not, after typing the above title, I was about to
search for the formula for calculating Body Mass Index (BMI)
when the mail arrived with a communication thanking me for my
participation in the NIH-AARP Diet and Health Study. I don’t
remember participating in the study but the letter contained a
form for calculating my BMI (703 times my weight in pounds
divided by my height in inches squared). My BMI figured out to
be 24.7, barely in the 18.5 to 24.9 range considered as normal. A
BMI in the 25.0 to 29.9 is “overweight” while anything over 29.9
is considered obese.
The bottom line of the “short sleep” study is in the title of the
paper. Leptin and ghrelin are hormones. Leptin is the good guy
in this story – it’s a hormone that suppresses appetite. Ghrelin is
the bad guy – it increases feelings of hunger. The Stanford and
Wisconsin researchers presented results of an ongoing study
known as the Wisconsin Sleep Cohort Study involving over a
thousand volunteers. The volunteers were recruited from
Wisconsin state agencies and were between 30 and 60 years of
age. Sleep histories, sleep measurements, analyses of blood
samples after sleep and a host of other data were taken over a
period of years dating back to 1989. It’s a comprehensive study
with some subjects followed for over a decade.
The blood analyses are of most interest here. If we take 8 hours
as the optimum sleep time (more precisely, it seems that 7.7
hours may optimum, looking at the data), let’s consider those
who habitually get only 5 hours of sleep. In these sleep-deprived
individuals, the level of leptin goes down about 15 percent from
the normal value. At the same time, the amount of ghrelin
hormone goes up, also about 15 percent. So what happens?
With a 3-hour sleep deficit, you’re hungrier than normal (extra
ghrelin) and there’s not enough leptin to tell you to stop before
you have that second cheeseburger and extra fries!
The 2004 paper is rather extensive and complex. Taheri, in the
Reuters dispatch this month, puts things more crisply for children
and adolescents. He would ban TVs, computers, cell phones,
iPods and the like from their bedrooms, noting that children who
are tired from lack of enough sleep also tend not to get enough
exercise, compounding the overweight problem. For any parents
out there, good luck! Taheri does say that you can let that
adolescent of yours sleep in on weekends but suggests no more
than 2 or 3 hours beyond normal wakeup time. Too much longer
and the body’s clock is thrown out of sync.
Let me digress for a few remarks about the 2004 paper and its
publication in the Public Library of Science Medicine, a journal
with which I was unfamiliar. Normally, when I go to the Web
site of a journal and try to access the text of a paper in the
journal, I am unable to do so unless I’m a subscriber, a member
of the society publishing the journal or am willing to pay a fee
for the particular article. The Public Library of Science,
however, is an open access journal and the reader is free to copy,
use or distribute its articles so long as there’s attribution.
Al this is great for me and for others wanting to read these open
access papers. But what if you’re The Electrochemical Society,
the American Chemical Society or any other society publishing
scientific journals? Typically, these journals accept papers only
after they’re sent out for critical review. Authors, or the
institutions with which they are associated, generally pay page
charges to help support publication expenses. Naturally,
publishers of conventional journals, which today can be accessed
on the Internet, are very concerned about open access journals,
accessible to anyone without charge. One argument for open
access is that today many research projects are supported by the
government, and hence the taxpayer. The argument is that the
results of such studies should be open to all at no charge.
Personally, I’d rather sit in a comfortable chair reading an article
than staring at a computer screen. However, I do notice one
thing as I’ve aged – I often tend to nod off reading an article in a
magazine or a journal but not when I’m reading a similar article
on the Internet. Well, before I doze off writing this column, I’m
off to see the Drowsy Chaperone.
Allen F. Bortrum
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