Thirty per cent of Americans are getting fewer than six hours sleep a night, far short of the recommended eight hours that doctors say are optimal for good health.
Now a new survey reveals that sleep times vary among different ethnic groups, with African-Americans getting at least 34 minutes less sleep than Asians, Hispanics or Caucasians.
The National Sleep Foundation's 2010 Sleep in America poll is the first to study sleep patterns among ethnic groups. It raises some important questions about why different sections of society are sleeping less than others.
One of America's leading sleep experts, Dr Allan Pack, says that there are genetic variations that determine the amount of sleep people need, which may go some way towards explaining why some groups sleep less than others.
But the University of Pennsylvania professor says a more likely explanation involves socio-economic factors.
The study found that African-Americans and Hispanics were much more likely than Asians and Caucasians to lose sleep every night worrying about money and employment.
Seventeen per cent of African-Americans also reported doing job-related tasks in the hour before bedtime, more so than Asians (16%), Caucasians (9%) and Hispanics (13%).
"Many of these people are sleeping short, not because they don't understand the importance of sleep, but because of the pressures of their lives, having two jobs and all that type of stuff", says Dr Pack. He thinks it is economic pressure that is forcing them to cut back on their sleep.
"There is no question that the percentage of people who sleep less than six hours a night is increasing. But whether the recession has made an acute blip in that, I don't know," he says.
Overall, at least a third of Hispanics and African-Americans say they are kept awake at least a few nights a week by financial, relationship or health concerns. That is compared with a little over a quarter of Caucasians and Asians.
Dr Meir Kryger, director of research and education at Gaylord Sleep Medicine in Connecticut, thinks the data needs to be considered in a wider social context.
"There can be a lot of other things that impact your life, such as your education, whether you have a job, your socio-economic status and so forth.
"It is possible, for example, that somebody has a child sleeping in their bed at night because their culture says that's a good thing to do. But it could also be that they do that because they're poor and can't afford an extra bedroom for the child," Mr Kryger explains.
Busy bed-time routines
Among those with children, Asians (28%) and Hispanics (22%) were most likely to sleep in the same room as their children, compared with African-Americans (15%) and Caucasians (8%).
However, Caucasians were much more likely (16%) to share their bed with their pets than other ethnic groups.
"Pets don't just lie there for eight hours. They have the ability to disrupt your sleep," says Dr Kryger.
The survey shows that African-Americans have the busiest bedtime routines. Experts say the hour before bed is an important time to relax to help ensure a good night's sleep. But while African-Americans get less sleep than other ethnic groups, they also say they do not need it.
The poll also found that 20-30% of all those questioned said they missed work or family functions because they were too tired.
About 24% of Asians, 22% of African-Americans and Hispanics and 19% of Caucasians missed an event at least once a month because of sleep problems.