An apple a day keeps the doctor away, but a dog could do even more.

Owning pets — and particularly dogs — has been linked to decreased risk of heart disease in humans, according to an American Heart Association statement published Thursday in the journal Circulation.

However, the AHA said the connection is not necessarily causal. "It may be simply that healthier people are the ones that have pets, not that having a pet actually leads to or causes reduction in cardiovascular risk," said Baylor professor Glenn N. Levine, M.D., who chaired the AHA committee that wrote the statement.

In a study of some 5,200 adults, the AHA found that dog owners walked more frequently than those who did not own pets, and were thus 54 percent more likely to get their recommended daily amount of exercise. In addition, researchers found a link between pet ownership and lower blood pressure and cholesterol levels, as well as reduced incidences of obesity.

The research also found that pets can help human bodies mitigate the effects of stress — which, as anyone who has taken a cat nap with a cat can attest, is absolutely true.

Here are more details of the research process from USA Today:

In one of the best-designed studies, Levine says, researchers compared people with borderline high blood pressure who adopted dogs with others who also wanted dogs but were randomly assigned to delay the adoptions for purposes of the study. Those who brought home their dogs saw declines in blood pressure and were less likely to see their blood pressure and heart rates rise in response to stress. A study with cats and dogs produced similar results in people with high blood pressure and high-stress occupations, he says.

Most other studies involved comparing pet owners with those who did not have pets, meaning researchers could not rule out the possibility that people who had pets were just healthier to start with. [USA Today]

As a result, the AHA cautioned against people rushing to adopt pets in hopes of immediately improving their health.

"In essence, data suggest that there probably is an association between pet ownership and decreased cardiovascular risk," said Levine. "What’s less clear is whether the act of adopting or acquiring a pet could lead to a reduction in cardiovascular risk in those with pre-existing disease. Further research, including better quality studies, is needed to more definitively answer this question."