mid-afternoon nods, a small study suggests.
A jolt of java may also help to overcome daytime sleepiness, British
What doesn't seem to work, the study showed, is trying to grab some extra
winks in the morning in an effort to ward off problems later in the day.
"Of the three, the nap is best," says Clare Anderson, PhD, of the
Sleep Research Centre at Loughborough University in Leicestershire, England.
"But coffee beats nothing."
The so-called afternoon dip -- a high propensity to nod off between 1 p.m.
and 3 p.m. despite a good night's rest -- is a well-known phenomenon.
Anderson presented the findings here at SLEEP 2008, the 22nd Annual Meeting
of the Associated Professional Sleep Societies.
nap? What is your favorite time of day to nod off for 15 or 20 minutes?
Take our poll and get feedback from our expert on WebMD's
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Nap Best, but Coffee Helps Too
The study involved 20 healthy 20-somethings who were what the researchers
call "good sleepers," averaging nearly seven-and-one-half hours of
uninterrupted sleep a night.
All underwent three interventions designed to combat daytime sleepiness: A
20-minute nap at 2:30 p.m.; a strong cup of coffee containing 150 milligrams of
caffeine at 2 p.m.; or 90 extra minutes of sleep in the morning. The three
nod-fighters were given a week apart.
Testing in the sleep lab showed that:
- The nap improved daytime sleepiness, compared to both no intervention and
getting extra winks in the morning.
- A cup of coffee reduced sleepiness in the afternoon, compared to doing
- An extra 90 minutes of sleep was associated with no improvement in daytime
If you're a normal sleeper, getting seven or eight hours of sleep a night,
then getting extra sleep in the morning doesn't really help, Anderson says.
None of the interventions -- not even the mid-day caffeine boost -- kept the
participants up at night.
That could be because people who didn't normally consume caffeinated drinks
were excluded from the study, she says. "In the U.K., we're used to
drinking a fair amount of [caffeinated] tea every day, so the cup of coffee
didn't affect their sleep."
20 Minutes Optimal Length for Midday Nap
American Academy of Sleep Medicine spokesman Sanjeev Kothare, MD, advises
against drinking caffeinated beverages too late in the day. "If you drink
one at 4 p.m., for example, it will linger in your system until almost
midnight," he says.
Kothare, a sleep specialist at Harvard Medical School, notes that although
siestas are encouraged in some cultures, they are typically
"impractical" for Americans.
But if you can fit in a midday nap, 20 minutes is just right, he tells
Research has shown that after a 10-minute nap, participants awoke feeling a
little refreshed, but soon felt sleepy again. After a 40-minute siesta, on the
other hand, they work up feeling groggy, according to Kothare.
"Twenty minutes proved optimal in terms of subsequently feeling
alert," he says.
By Charlene Laino
Reviewed by Louise Chang
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