Americans are working more and sleeping less, according to a new study. Researchers found that paid work is the most common reason people sacrifice sleep, and suggest that chronic sleep problems could be reduced through the adoption of flexible starting times.

Short sleepers, those who average six hours of sleep or less, were found to work 1.55 hours more than others on weekdays, and an additional 1.86 hours on weekends and holidays. These people were found to start work earlier, and stay longer before coming home, than people who sleep for longer periods. Workers with more than one job are 61 percent more likely than others to be short sleepers.

"Potential intervention strategies to decrease the prevalence of chronic sleep loss in the population include greater flexibility in morning work and class start times, reducing the prevalence of multiple jobs, and shortening morning and evening commute times," Mathias Basner, lecturer on sleep and chronobiology in psychiatry at the University of Pennsylvania Perelman School of Medicine, said.

Researchers discovered that for each hour extra in the morning before the start of work, sleep times increased by 20 minutes. Workers and students who started each morning at six a.m. or earlier averaged just six hours of sleep each night. Those who start school or work between nine and 10 in the morning slept an average of 7.29 hours during each cycle. Perhaps surprisingly, self-employed people were 17 percent less likely than others to be short sleepers, perhaps due to flexible schedules.

The U.S. Bureau of Labor Statistics conducted the study, which was conducted through a telephone survey of 124,517 people age 15 or older. The survey was conducted between 2003 and 2011. Investigators studied time spent in immediate activities which usually take place just before or after sleeping, including socializing, watching television or grooming. Significant time was spent by subjects commuting to and from work. This suggests that reducing commuting time could play a pivotal role in reducing sleep deprivation.

About 40 percent of U.S. workers get less than seven to nine hours of sleep each night, which is usually recommended by health care professionals. One-third of American workers average six hours of sleep each night or less.

Researchers found that males and those with higher incomes were more likely than the general population to be short sleepers. Unemployed people, retirees and those who do not work were found to be the most likely to sleep for longer periods of time each night.

Sociodemographic Characteristics and Waking Activities and their Role in the Timing and Duration of Sleep was published in the journal Sleep, detailing results of the study.