The findings come from a study of nearly 4,300 workers in Texas cities whose daily commute times were compared to their odds of various health risk factors.
"Previous studies have looked at sedentary behavior like TV viewing and total time spent driving," said study lead author Christine Hoehner, an assistant professor in the division of public health sciences at the Washington University School of Medicine in St. Louis. "But we wanted to look specifically at commuting distance, since it's an important part of people's daily routine."
"What we found ... is that long commutes can take away from exercise and are associated with high blood pressure, higher weight and generally lower fitness levels," Hoehner said. "This may make a lot of sense, because it's extremely intuitive. But it nonetheless suggests that longer commutes are really getting under the skin and affecting people's health."
The findings appear in the June issue of the American Journal of Preventive Medicine.
According to the researchers, the number of workers driving to work by private car more than doubled between 1960 and 2000, increasing from more than 41 million to nearly 113 million. The average distance traveled to work also has grown in recent years, from nearly nine miles in 1983 to more than 12 miles in 2001, the researchers said.
The new study focused on adult Texans living in either the Dallas/Fort Worth or Austin regions.
No participant had a history of heart attack, stroke or diabetes, and none were pregnant. All were employed in jobs that required a commute of some kind.
At some point between 2000 and 2007, all participants underwent comprehensive medical exams, including treadmill runs designed to assess their heart and lung fitness. They also reported their level of daily exercise during the three months prior to the study.
The team found that people with the longest commuting distances also tended to exercise less than those with short commutes. They also had lower levels of cardiorespiratory fitness, a higher body-mass index (a measure of body fat based on height and weight), a wider waistline and higher blood pressure.
Specifically, commutes of 10 miles or more were linked to higher blood pressure levels, while those of more than 15 miles were linked to higher odds of obesity and a lower likelihood of meeting public-health physical-activity recommendations, the team found.
These trends didn't disappear even after the researchers factored in time spent exercising, which suggests that there is something about the commute itself — outside of its impact in lowering exercise rates — that harms cardiovascular health.
"This would suggest that drivers of long distances are burning fewer calories overall, even if they are exercising the same amount as drivers of shorter distances," Hoehner said. "Although we didn't measure it, stress is also a possible mechanism at play, especially if commuters are faced with travel congestion."
What to do? "People can't easily move closer to their job or change their job ... which means commuting by car is different from other types of [unhealthy] sedentary behavior that are more modifiable, such as watching TV," Hoehner said.
"The message here is that people need to find creative ways to build physical activity into their days," she said. "And that could be as simple as walking more throughout the day, whenever one can. That could be made more feasible if offices were to encourage physical-activity breaks during the day, and perhaps even flex time so people can drive to work outside rush hour."
One expert said attitude is important in increasing exercise rates.
For busy people, "the key is not being intimidated by exercise," said Dr. Bryan Henry, an assistant professor of medicine at the University of Rochester Medical Center in Rochester, N.Y.
"No one after an hour-long commute home from work is going to want to jump on a elliptical machine," Henry said. "But just short exercise commitments can work. That could mean walking farther from the parking lot or taking a 10-minute walk here and there. It can easily add up to the equivalent of a 40-minute brisk walk."