TELEVISION WATCHERS DIE SOONER? Perhaps sitting for extended periods is bad for you — I can believe that. On the other hand, perhaps people who just don’t feel very good are more likely to watch a lot of TV. In which case the TV-watching is a marker, not a cause, of underlying problems.

UPDATE: Reader Barry Krakow, a physician who heads a sleep-disorder clinic, writes:

TV is a marker. Patients with more severe sleep problems watch more tv because they lack the energy to trigger their natural motivation to do something more active. We see this problem all the time in sleep medical centers, and as you would expect for lots of reasons, sleep disorders decrease longevity. One of the most remarkable things to see in our clinical practice is the patient, who after less than two months of treatment, abandons the boob tube and heads for the gym, golf course or a run around the neighborhood. Sleep medicine is a very rewarding field, almost a form of near instant gratification!

Sleep deprivation is an underappreciated problem.