David Dinges says suburban sprawl may be doing more than gobbling up green space and making Americans over-dependent on their cars.

That sprawl, he says, may actually be killing us.

Dinges, a Penn professor of psychology in psychiatry, runs one of the most renowned sleep labs in the world. His groundbreaking work on sleep loss and humans’ ability to function—or not—when they don’t get enough sleep has put him at the forefront of his field, as he’s conducted research for government clients ranging from NASA to the Air Force to the Department of Defense.

Recently, however, Dinges embarked on a new track of research that got him out of the sleep lab and deep into America’s culture. The result is a study that offers surprising revelations about how the daily activities of Americans affect their sleep health.

The one standout finding? That urban planning failures, and the increased commute times that have resulted, may be robbing us of our sleep—and, by extension, our health. “Many new studies were showing that short sleep duration—below 7 hours—is associated with increased risk of obesity, and also of mortality,” Dinges says. “We don’t know if that’s causal. But if it’s true [that] sleep loss produces impairment and changes to the physiological response ... [we wondered]: Where is all the sleep going? When people are sleeping less, what’s causing them to sleep less?”

To find the answers, Dinges and his team turned to the American Time Use Survey, a huge report published by the U.S. Department of Labor. Created originally as an economics tool, Dinges found the report also held great value for his work.

For the survey, government pollsters asked respondents to recount, in exacting detail, how they spent each minute of the 24-hour period prior to the survey. The result is a report that offers great insight into how much time Americans spend working, caring for children, going to school, traveling and, of course, sleeping.

“We went into this database,” says Dinges, “and we asked: What is the relationship between sleep time and all the other time that people spend?” Surprisingly, Dinges says, his team found no connections between most of the things American do and their sleep habits. Mowing the lawn, going out on the town, doing the laundry, exercising, even caring for children—none of these activities seemed to have any impact whatsoever on sleep.

There was just one notable exception: Travel time. Travel, a survey category that included everything from running errands to driving to work, jumped out as a major contributing factor to poor sleep habits. “It was an inverse relationship,” Dinges explains. “The more time people spent traveling, the less time they spent sleeping.”

Looking deeper, Dinges then explored how commuting, specifically, impacted sleep habits. He found Americans who live more than a 25-minute drive from work get significantly less sleep than Americans who live closer to work. The reasons for that aren’t yet clear, though Dinges and his team are looking deeper to find those answers now.

Given that other studies are showing that U.S. commute times are only getting longer, Dinges’ research seems to suggest that more Americans are going to be getting less sleep in years to come.

“The way we plan our cities is contributing to us spending more time traveling and less time sleeping,” Dinges says.

While Dinges says much more work remains to be done, and admits many more connections must be made between travel time, urban planning, sleep habits and overall health, he says early results clearly indicate that our health is being compromised by our commute times.
And if that’s the case, Dinges wonders, doesn’t it suggest that American urban planning may need to be revisited?

“I think this opens up another domain for consideration, around what the consequences are in terms of our modern lifestyle and how that’s associated with lack of adequate sleep and the increased health risks because of them,” he says. “One of them may be that we may be losing sleep because we’re spending so much time sitting on our backsides traveling.”

Originally published on November 16, 2006.