To Members and Friends of the Los Angeles Gerontology
Sleep duration and longevity. But what happens if you change
time zones x 8? — Steve Coles
“Why Seven Hours of Sleep Might Be
Better Than Eight:
Sleep Experts Close in on the Optimal Night’s
July 21, 2014; (WSJ) — It’s the holy grail of questions: How many
hours of sleep should we ideally get per night? We’ve heard the magic
number eight, but experts are working to come up with a more refined,
evidence-based number. WSJ’s Sumathi Reddy joins Tanya Rivero on Lunch
Break with the details. Photo: iStock/dolgachov
How much sleep do you really need?
Experts generally recommend seven to nine hours a
night for healthy adults. Sleep scientists say new guidelines are needed
to take into account an abundance of recent research in the field and to
reflect that Americans are on average sleeping less than they did in the
Several sleep studies have found that seven hours is
the optimal amount of sleep -Â not eight, as was long believedÂwhen it
comes to certain cognitive and health markers, although many doctors
question that conclusion.
Other recent research has shown that skimping on a
full night’s sleep, even by 20 minutes, impairs performance and memory
the next day. And getting too much sleep -Â not just too little of it -Â
is associated with health problems including diabetes, obesity, and
cardiovascular disease and with higher rates of death, studies
mortality and morbidity is with seven
hours,” said Shawn Youngstedt, a Professor
in the College of Nursing and Health Innovation at Arizona State
University Phoenix. “Eight hours or more has consistently been shown
to be hazardous,” says Dr. Youngstedt, who researches the effects of
The Way We Sleep
People say they need an average of 7 hours, 13 minutes of sleep to
function at their best. They sleep 6 hours, 31 minutes on an average
weekday, and 7 hours, 22 minutes on weekends.
69% of Americans get less sleep on weekdays than they say they need.
Sleeping with a partner is preferred by 60% of adults. About 1 in 5
people sleep with a pet.
Pajamas are worn by 73% of people and 12% sleep with nothing on.
A third of adults sleep with one pillow, 41% use two and 14% keep
four or more pillows.
Source: National Sleep Foundation, 2013 International Bedroom
The Centers for Disease Control and
Prevention is helping to fund a panel of medical specialists and
researchers to review the scientific literature on sleep and develop new
recommendations, probably by 2015. Daniel F. Kripke, an Emeritus
Professor of Psychiatry at the University of California San Diego,
tracked over a six-year period data on 1.1 million people who
participated in a large cancer study. People who reported they slept [6.5
to 7.4] hours had a lower mortality rate than those with shorter or
The study, published in the Archives of General Psychiatry in 2002,
controlled for 32 health factors, including medications.
In another study, published in the journal Sleep
Medicine in 2011, Dr. Kripke found further evidence that the optimal
amount of sleep might be less than the traditional eight hours. The
researchers recorded the sleep activity of about 450 elderly women using
devices on their wrist for a week. Some 10 years later the researchers
found that those who slept fewer
than five hours or more than 6.5 hours had a higher
Other experts caution against studies showing ill
effects from too much sleep. Illness may cause someone to sleep or spend
more time in bed, these experts say. And studies based on people
reporting their own sleep patterns may be inaccurate.
“The problem with these studies is that they give
you good information about association but not causation,”
said Timothy Morgenthaler, President of the American Academy of Sleep
Medicine, which represents sleep doctors and researchers, and a Professor
of Medicine at the Mayo Clinic Center for Sleep Medicine.
American adults get less sleep today than in the past,
research shows. Corbis
Dr. Morgenthaler advises patients to aim for seven to
eight hours of sleep a night and to evaluate how they feel. Sleep needs
also vary between individuals, largely due to cultural and genetic
differences, he said.
Getting the right amount of sleep is important in
being alert the next day, and several recent studies have found an
association between getting seven hours of sleep and optimal cognitive
the journal Frontiers in Human Neuroscience last year used data from
users of the cognitive-training website
Researchers looked at the self-reported sleeping habits of about 160,000
users who took spatial-memory and matching tests and about 127,000 users
who took an arithmetic test. They found that cognitive performance
increased as people got more sleep, reaching a peak at seven hours before
starting to decline.
After seven hours, “increasing sleep was not any
more beneficial,” said Murali Doraiswamy, a Professor of Psychiatry
at Duke University Medical Center in Durham, NC, who co-authored the
study with scientists from Lumos Labs Inc., which owns Lumosity.
He said the study replicated earlier research, including a look at memory
loss. “If you think about all the causes of memory loss, sleep is
probably one of the most easily modifiable factors,” he said.
Most research has focused on the effects of getting
too little sleep, including cognitive and health declines and weight
gain. David Dinges, a sleep scientist at the University of Pennsylvania’s
Perelman School of Medicine who has studied sleep deprivation, said
repeatedly getting just 20 or 30 minutes less than the minimum
recommendation of seven hours can slow cognitive speed and increase
Experts say people should be able to figure out their
optimal amount of sleep in a trial of three days to a week, ideally while
on vacation. Don’t use an alarm clock. Go to sleep when you get tired.
Avoid too much caffeine or alcohol. And stay off electronic devices a
couple of hours before going to bed. During the trial, track your sleep
with a diary or a device that records your actual sleep time. If you feel
refreshed and awake during the day, you’ve probably discovered your
optimal sleep time.
The new sleep guidelines will be drawn up by a panel
of experts being assembled by the American Academy of Sleep Medicine, the
Sleep Research Society, an organization for sleep researchers, and the
CDC. The recommendations are meant to reflect evidence that has emerged
from scientific studies and are expected to take into account issues such
as gender and age, says Dr. Morgenthaler, the academy president.
Another group, the National Sleep Foundation, a
nonprofit research and advocacy group, also has assembled an expert panel
that expects to release updated recommendations for sleep times in
These groups currently recommend [seven to nine] hours
of nightly sleep for healthy adults. The
National Heart, Lung and Blood Institute recommends seven to eight
hours, including the elderly. Most current guidelines say school-age
children should get at least 10 hours of sleep a night, and teenagers, [9
“I don’t think you can overdose on healthy sleep.
When you get enough sleep your body will wake you up,” said Safwan
Badr, Chief of the Division of Pulmonary, Critical Care, and Sleep
Medicine at Wayne State University School of Medicine in
in the current issue of Journal of Clinical Sleep Medicine seemed to
confirm that. Five healthy adults were placed in what the researchers
called Stone-Age-like conditions in Germany for more than two months -Â
without electricity, clocks, or running water. Participants fell asleep
about two hours earlier and got on average 1.5 hours more sleep than was
estimated in their normal lives, the study said. Their average
amount of sleep per night: 7.2 hours.Write to Sumathi Reddy at
L. Stephen Coles, M.D., Ph.D., Cofounder
Los Angeles Gerontology Research GroupE-mail: firstname.lastname@example.orgE-mail: