Slate blogger Matthew Yglesias, a center-left economics writer whose work I generally enjoy reading, has a new post up with the title, “Long Commutes Make You Fat, Give You High Blood Pressure.” Scary stuff, huh? In his post, he cites a new article in the June issue of the American Journal of Preventive Medicine, “Commuting Distance, Cardiorespiratory Fitness, and Metabolic Risk” (gated, pp. 571-578). The study found that longer commute times in the Dallas-Ft. Worth metropolitan area led to decreased physical activity and cardiorespiratory fitness, as well as elevated blood pressure.
Yglesias arrives at the following conclusions:
In other words, a long commute is definitely bad for your blood pressure but it’s positively disastrous if it ends up eating into your physical activity time. So a longish walk or bike ride to work probably isn’t that bad, but a long drive is disastrous. I really firmly believe that the existence of persistent regular traffic jams is just about the most underrated problem in American public policy, especially because it’s a problem we could almost certainly solve relatively easily with a mix of congestion pricing, demand-responsive pricing of street parking, and more bus service.
I wholeheartedly agree with him on his solutions to traffic congestion, which is indeed one of the most underrated problems in American public policy. In the public policy world, most attention to congestion focuses on the social costs — wasted fuel and the resulting local air pollution, and the delays to commutes and freight movements. This, I believe, is where public policy’s focus should be. That said, of course there are private costs — and one type of cost is the negative health impact (specifically higher blood pressure) of congestion-caused stress.
The discussion section of the paper provides a solid explanation of this phenomenon:
Multiple mechanisms could be contributing to this relationship. First, automobile driving has been identified as a salient source of everyday stress, especially when drivers are faced with traffic congestion. Because the Dallas–Fort Worth region is ranked among the top five most congested metropolitan areas in the U.S., those with longer commutes may be more likely to be exposed to heavy traffic resulting in higher stress levels and more time sitting. Daily commuting represents a source of chronic stress that has been correlated positively with physiologic consequences including high blood pressure, self-reported tension, fatigue, and other negative mental or physical health effects in some studies.
But of course there are other confounding variables. While certainly less scientific, a Gallup poll released earlier this year on the relationship between stress and “worker engagement” found that those employees who managers typically refer to as “good employees” are not particularly stressed by long commutes. Gallup offers the following definitions:
Engaged employees are involved in and enthusiastic about their work. Those who are not engaged may be satisfied but are not emotionally connected to their workplaces and less likely to put in discretionary effort. The actively disengaged are emotionally disconnected from their work and workplace, and these workers jeopardize the performance of their teams.
What the Gallup poll found is that commute time has essentially no impact on “engaged employees'” self-reported stress levels. Of those surveyed who were categorized as “engaged,” 2.9 percent of those with commute times of 15 minutes suffered from a lot of daily stress; of those with commute times of 45 minutes or more, 2.3 percent suffered from high levels of stress. Only when taking into account lower-quality employees do commute times seem to correlate with stress levels. (One caveat: of course there are situations where higher-ups make the workplace unbearable, and many workers suffering from poor work environments would likely fall into the 52 percent of Americans who are not actively engaged at their jobs.)
Now back to the study. While it offers some interesting new information, it is important to understand its limitations. One big limitation is that this study consisted of a single longitudinal patient population at the Cooper Clinic in Dallas, Texas. Indeed, the authors admit to the “limited generalizability of the study population, consisting of predominantly white, well-educated, and healthier adults of middle-to-upper [socio-economic status] and underrepresentation of women. Although the homogeneity of the population with respect to education and race/ethnicity may improve internal validity, some residual confounding may be present because of other unmeasured socioeconomic variables (e.g., occupation and income).”
The study also fails to consider transportation mode, although we can hardly blame the authors — mass transit is a trivial mode in Dallas-Ft. Worth. I only mention this because New York City, generally associated with idealistic urbanism and often used as a model by the anti-sprawl movement, suffers from some of the longest commute times in the nation. In fact, unless you live and work near the same transit line, your commute will likely take longer via mass transit than it does by private automobile once you factor in transfers and traveling to and from transit stations [PDF, p. 11]. Dense city living is also associated with an increase in mental disorders and stress.
So if blood pressure is your main concern as a sub-par employee, fleeing sprawl in a probably futile attempt to reduce your stressful commute time may be a bad idea. If you have read Yglesias’s post, which is quite good, please try to keep all of this in mind.