(Reuters Health) - One third of U.S. adults say they sleep less than six hours a night, which is 15 percent more than were getting too little sleep 15 years ago, researchers say.

The trend toward increasing numbers of people getting too little shuteye started in 2013, the study team reports in the journal Sleep. Most of this recent shift from adequate to inadequate sleep duration was among Hispanic and non-Hispanic black adults, widening racial and ethnic disparities in sleep, and potentially disparities in health.

“Sleep is important for everything we do, including work, our relationships and health,” said lead study author Connor Sheehan of Arizona State University in Tempe, in a phone interview. “People can’t always accurately report exactly how long they sleep, but they have a decent idea of if they’re sleeping well or not.”

He and his colleagues examined data from an annual, nationally-representative health interview survey collected between 2004 and 2017. A total of 398,382 participants were asked how much they slept in a 24-hour period. The researchers defined short sleep as six hours or less, adequate sleep as seven to eight hours and long sleep as nine or more hours.

The proportion of people with short-sleep duration was relatively stable from 2004 to 2012 at about 28-29 percent. The majority, 63 percent, got seven to eight hours of sleep during this period, and 8.5 percent slept nine hours or more.

In 2013, the proportion reporting short sleep rose to 29 percent, and kept increasing to 33 percent in 2017. By 2017, the proportion of people reporting adequate sleep had fallen to 60 percent, and long-sleepers were down to 7 percent.

The 15 percent increase from 2013 to 2017 in people across the U.S. getting too little sleep “might not sound like a lot . . . but at 9 million people, that’s the population of New York City reporting short sleep,” Sheehan said. “It’s a nontrivial number and a canary in the coal mine for our future health outcomes.”

Hispanics and non-Hispanic blacks were more likely to report short sleep. By 2017, about 31 percent of white survey participants, 42 percent of black participants and 33 percent of Hispanic participants were sleeping six or fewer hours.

And the black and Hispanic groups made up the larger share of the increase in short sleeping over time. For white participants, the likelihood of reporting short sleep rose 2 percentage points between 2004 and 2017, while for both Hispanic and black participants it rose by 7 percentage points.

These racial and ethnic differences were not explained by markers of social advantage, such as income or education, or differences in physical or mental health, the authors write.

“It is likely that there are structural factors that interfere with adequate sleep. Black and Latino Americans have and continue to live in very different neighborhoods compared to white Americans,” said Margaret Hicken of the University of Michigan in Ann Arbor, who wasn’t involved in the study.

“Furthermore, Black and Latino Americans experience greater social stressors that do not center necessarily on poverty or crime but include the more common need to be continually vigilant about navigating everyday life in a racially-hierarchical society,” she told Reuters Health by email.

Although this study reports a drop in sleep in recent years, sleep researchers believe Americans are more aware of the importance of sleep, which is a positive step.

“People are slowly getting it. We’re getting more interested in sleep,” said Dr. Mathias Basner of the University of Pennsylvania Perelman School of Medicine in Philadelphia, who wasn’t involved in the study.

“People are less frequently watching TV or looking at their phones right before bed,” Basner said in a phone interview. “We’re starting to see a change in behavior.”

SOURCE: bit.ly/2Q8nAZl Sleep, online November 27, 2018.