Americans who log long hours on the job find the time for leisure and other activities by cutting down on sleep, a study reports today.
"We only have 24 hours in a day," says Mathias Basner, a researcher at the University of Pennsylvania School of Medicine.
His study of 47,731 Americans found that people who worked more simply got up earlier or went to bed later — a practice that puts them at risk of sleep deprivation.
Time spent at work is the single biggest determinant of how much sleep Americans got on a typical day, according to the study in the Sept. 1 issue of the journal Sleep.
But travel time, including time sitting in traffic on the way to work, comes in second place, Basner says.
"You could argue there's a hidden cost to living in suburbia," says Gregory Belenky, director of the Sleep and Performance Research Center at Washington State University in Spokane. People who live in sprawling urban areas often make a long workday even longer when they try to run errands on clogged roads, he says.
Basner says sleep deprivation has been linked to a number of serious health problems, including obesity.
People who are chronically sleep-deprived also can experience attention lapses, memory loss and other difficulties that can impair performance on the job, says James Walsh, executive director of the sleep medicine and research center at St. Luke's Hospital in St. Louis.
And fatigue can add an element of danger to an already stressful commute. "If you're only sleeping five hours a night, you're at risk of falling asleep at the wheel," Walsh says.
The National Sleep Foundation estimates that sleep-deprived drivers cause more than 100,000 automobile crashes a year and more than 1,500 deaths.
Basner's team analyzed the results of a federal survey conducted in 2003 through 2005. People were asked to account for their time over a 24-hour period.
The survey suggests that people who cut back on sleep on weekdays often try to sleep in on Saturday and Sunday. But people who cut back on sleep night after night might never catch up, Walsh says.
Surveys suggest Americans get about 6½ hours of sleep a night — about an hour less than the average in the 1950s, he says. Today, many adults extend their workdays by using cellphones to check e-mail messages.
A second study in Sleep suggests that teens who use cellphones after lights out can have daytime sleepiness.
The teens in this study lived in Europe, but teens in the USA also use cellphones to text-message and chat with friends at all hours, says Amy Wolfson of the National Sleep Foundation.
"We're living in a 24/7 culture, and teens are mimicking adults," she says.
Says Walsh: "People feel that sleep is negotiable." Yet studies suggest that most adults need from seven to eight hours of sleep a night, and teens need nine hours or more in order to do their best during the day, he says.