Gretchen Reynolds, in NYT Well, references an article in “Medicine and Science in Sports and Exercise” by TY Warren et al. “Well” focuses on one finding — that men who spent more than one full day a week sitting either in a car or on a couch (watching TV) had a 64% greater risk of dying from cardiovascular disease (CVD). And, as Alan Durning has noted in reporting findings from another study, the correlation holds regardless of whether the men regularly did high-impact exercise (e.g., team sports, gym workouts). Avoiding CVD appears to be more about staying in motion constantly, rather than sporadic bursts of activity interrupting otherwise sedentary behavior — exactly the patterns of activity that active communities and suburban sprawl respectively foster.
What I thought was even more interesting, though, is that the article notes a higher correlation between sitting in cars and CVD than watching TV and CVD. Indeed, it appears that hours spent watching TV aren’t significantly correlated with risk of death from CVD — but that spending more than 10h a week in a car (=2h/weekday) leads to an 82% (!) higher risk of death from CVD than spending less than 4h a week (=48min/weekday) in a car.