DSPS is often confused with insomnia, perhaps because sufferers seem sluggish and tired during the day. But the two disorders are actually very different: Insomniacs have trouble with the actual process of falling asleep, often due to anxiety or other factors. People with DSPS sleep perfectly fine during the hours their bodies tell them to. And DSPS isn't simply the preference to be a “night owl”—DSPS sufferers can’t fall asleep early even if they want to.

All of this amounts to bad news for DSPS sufferers in the world of work. According Cary Cooper, a psychologist and professor at Lancaster University Management School, when people who have DSPS wake up early for work, they become sleep deprived which causes them to be less efficient, innovative, and creative at the office. People with DSPS have trouble finding positions that allow them to work hours that let them get enough sleep. This also results in more stress, and can cause workplace accidents. A 2010 Journal of Occupational and Environmental Medicine study found that sleep deprivation costs companies an average of $2000 a year per worker.

“The evidence is clear,” Cooper says. “We’re losing quite a lot of talent.”

Of course, humans didn't always work 9-to-5 or sleep eight recommended hours at night. Anthropologist Carol Worthman describes the sleep patterns of hunter-gather societies as having huge variations across different tribes and cultures. While for some tribes, sleeping at the same time was a social activity, other tribes slept whenever they could or felt like it. A good deal of research suggests humans aren’t made to sleep eight-hour stretches. The 9-to-5 workday started as a movement in the 1830s. Laws were passed over the next few decades, with Congress passing the eight-hour workday for federal employees in 1876. The 40-hour workweek became part of the New Deal, which is when it became more or less standardized.

DSPS sufferers are perhaps a small population that's benefitting greatly from the growth of flexible work in our economy. Peter Mansbach, a software engineer with degrees from Harvard and Brandeis University, worked in robotics at the National Institute of Standards and Technology. But his body wouldn't align with his workday schedule; his 8 a.m. start time made him sick. He ended up losing his job, so he switched into computer programming—where he found contract work with flexible hours. Unfortunately, being a contract worker meant not getting promoted or having the job stability of someone who could be in the office.

Mansbach has since founded the Circadian Sleep Disorders Network, a volunteer-run support and advocacy group for people with internal clock disorders. "Most people with [DSPS] don’t know about it," Mansbach says. "I get emails from people who say, 'I just discovered your site. I've always doubted myself; people called me lazy. It's great to know there's a real problem here.'"