For a small group of people???perhaps just 1% to 3% of the population???sleep is a waste of time.
Natural "short sleepers," as they're officially known, are night owls and early birds simultaneously. They typically turn in well after midnight, then get up just a few hours later and barrel through the day without needing to take naps or load up on caffeine.
They are also energetic, outgoing, optimistic and ambitious, according to the few researchers who have studied them. The pattern sometimes starts in childhood and often runs in families.
While it's unclear if all short sleepers are high achievers, they do have more time in the day to do things, and keep finding more interesting things to do than sleep, often doing several things at once.
Nobody knows how many natural short sleepers are out there. "There aren't nearly as many as there are people who think they're short sleepers," says Daniel J. Buysse, a psychiatrist at the University of Pittsburgh Medical Center and a past president of the American Academy of Sleep Medicine, a professional group.
Out of every 100 people who believe they only need five or six hours of sleep a night, only about five people really do, Dr. Buysse says. The rest end up chronically sleep deprived, part of the one-third of U.S. adults who get less than the recommended seven hours of sleep per night, according to a report last month by the Centers for Disease Control and Prevention.
To date, only a handful of small studies have looked at short sleepers???in part because they're hard to find. They rarely go to sleep clinics and don't think they have a disorder.
A few studies have suggested that some short sleepers may have hypomania, a mild form of mania with racing thoughts and few inhibitions. "These people talk fast. They never stop. They're always on the up side of life," says Dr. Buysse. He was one of the authors of a 2001 study that had 12 confirmed short sleepers and 12 control subjects keep diaries and complete numerous questionnaires about their work, sleep and living habits.One survey dubbed "Attitude for Life" that was actually a test for hypomania. The natural short sleepers scored twice as high as the controls.
There is currently no way people can teach themselves to be short sleepers. Still, scientists hope that by studying short sleepers, they can better understand how the body regulates sleep and why sleep needs vary so much in humans.
"My long-term goal is to someday learn enough so we can manipulate the sleep pathways without damaging our health," says human geneticist Ying-Hui Fu at the University of California-San Francisco. "Everybody can use more waking hours, even if you just watch movies."
Dr. Fu was part of a research team that discovered a gene variation, hDEC2, in a pair of short sleepers in 2009. They were studying extreme early birds when they when they noticed that two of their subjects, a mother and daughter, g
ot up naturally about 4 a.m. but also went to bed past midnight.
Genetic analyses spotted one gene variation common to them both. The scientists were able to replicate the gene variation in a strain of mice and found that the mice needed less sleep than usual, too.
News of their finding spurred other people to write the team, saying they were natural short sleepers and volunteering to be studied. The researchers are recruiting more candidates and hope to find more gene variations they have in common.
Potential candidates for the gene study are sent multiple questionnaires and undergo a long structured phone interview. Those who make the initial screening wear monitors to track their sleep patterns at home. Christopher Jones, a University of Utah neurologist and sleep scientist who oversees the recruiting, says there is one question that is more revealing than anything else: When people do have a chance to sleep longer, on weekends or vacation, do they still sleep only five or six hours a night? People who sleep more when they can are not true short sleepers, he says.
To date, Dr. Jones says he has identified only about 20 true short sleepers, and he says they share some fascinating characteristics. Not only are their circadian rhythms different from most people, so are their moods (very upbeat) and their metabolism (they're thinner than average, even though sleep deprivation usually raises the risk of obesity). They also seem to have a high tolerance for physical pain and psychological setbacks.
"They encounter obstacles, they just pick themselves up and try again," Dr. Jones says.
Some short sleepers say their sleep patterns go back to childhood and some see the same patterns starting in their own kids, such as giving up naps by age 2. As adults, they gravitate to different fields, but whatever they do, they do full bore, Dr. Jones says.
"Typically, at the end of a long, structured phone interview, they will admit that they've been texting and surfing the Internet and doing the crossword puzzle at the same time, all on less than six hours of sleep," says Dr. Jones. "There is some sort of psychological and physiological energy to them that we don't understand."
Drs. Jones and Fu stress that there is no genetic test for short sleeping. Ultimately, they expect to find that many different genes play a role, which may in turn reveal more about the complex systems that regulate sleep in humans.
Benjamin Franklin, Thomas Jefferson and Leonardo da Vinci were too busy to sleep much, according to historical accounts. Winston Churchill and Thomas Edison came close but they were also fond of taking naps, which may disqualify them as true short sleepers.
Nowadays, some short sleepers gravitate to fields like blogging, videogame design and social media, where their sleep habits come in handy. "If I could find a way to do it, I'd never sleep," says Dave Hatter, a software developer in Fort Wright, Ky. He typically sleeps just four to five hours a night, up from two to three hours a few years ago.
"It's crazy, but it works for me," says Eleanor Hoffman, an overnight administrator at Bellevue Hospital Center in New York who would rather spend afternoons playing mahjong with friends than sleep anymore than four hours. Sometimes she calls her cousin, Linda Cohen, in Pittsburgh about 4 a.m., since she knows she'll be wide awake as well???just like they were as kids.
"I come to life about 11 at night," says Mrs. Cohen, who owns a chain of toy stores with her husband and gets up early in the morning with ease. "If I went to bed earlier, I'd feel like half my life was missing."
Are you a short sleeper? For more information on the genetic study, contact Dr. Jones at firstname.lastname@example.org
Write to??Melinda Beck at??HealthJournal@wsj.com