MONTEREY, Calif. -- The well-known link between depression and fatal heart attacks may be mostly a result of lack of exercise by seriously depressed adults, scientists report today.
The hearts of depressed patients beat at a less variable rate than the hearts of the nondepressed, and this lower variability puts people at greater risk of dying.
New findings suggest "a significant part of low heart rate variability in depressed people can be attributed to lack of exercise," says Lana Watkins of Duke University Medical Center, who is presenting her findings at the American Psychosomatic Society meeting here.
In her studies with 350 heart disease patients, the higher their depression scores, the lower their heart rate variability. Also:
* Among the clinically depressed, 1 out of 4 rated themselves as extremely inactive, compared with one in 14 patients who weren't depressed.
* Depressed people averaged about half as much time per day as the nondepressed in moderate activity, such as fast walking.
* The more active a person was, the higher his heart rate variability.
In fact, after taking into account lower physical activity of depressed patients, being depressed was no longer linked to low heart rate variability. So that points to exercise as a key player here.
In another report at APS, depressed heart attack patients were about twice as likely as the nondepressed to fall in the range of heart rate variability that's predictive of death, says Robert Carney of Washington University Medical School in St. Louis.
The study of 800 patients is the largest ever done on depression and heart rate variability.
Another recent study by a team at Montreal Heart Institute found that depression raises the odds of dying from a second heart attack, but mostly in those who walk less than a block a day.
"It's kind of a chicken-or-egg thing," Carney says. "Do you become depressed because you don't exercise, or do you not exercise because you're depressed? The arrow probably goes in both directions.
"Either way, the smartest thing people with heart disease can do is to get aerobic exercise and seek treatment if they're depressed."
Our thanks to Les Posen for sending this in