People with heart disease who are more upbeat and excited tend to live longer than those who don't have such a positive outlook, a new study suggests, possibly because they are often more active.
Researchers surveyed people with ischemic heart disease - when the heart doesn't get enough blood due to narrowed arteries - and found earning a high score on measures of "positive affect" was tied to a greater chance of being a regular exerciser and a lower risk of dying over the next five years.
"It adds to the body of literature suggesting that there may be relationships between positive affect … and all-cause mortality," Richard Sloan, who studies psychological risk factors and heart disease at Columbia University Medical Center in New York, said.
But, "It's going to take more than this to be confident that there's a link in the way we're confident there's a link between depression and (a higher risk of) heart disease," Sloan, who didn't participate in the new research, told Reuters Health.
The new study included 607 heart patients who were seen at one Danish hospital.
Susanne S. Pedersen from Tilburg University in The Netherlands and her colleagues asked the patients about their quality of life, mood and lifestyle habits including physical activity in 2005. Then they used death and hospital records to track participants through 2010.
On a mood scale ranging from 0 to 40, where higher scores indicate feeling more relaxed, self-confident and excited, half of participants scored a 24 or above. (Negative affect was measured separately - so a person could score high or low on measures of both positive attitude and insecurity or helplessness.)
During the follow-up period, 30 of the high positive affect patients died of any cause, compared to 50 people with a lower positive attitude score.
Some of that association appeared to be driven by exercise habits, the researchers found. People with high mood scores were more likely than other participants to say they exercised at least once a week, and exercisers were half as likely to die as non-exercisers.
There was not a clear difference, however, in how often people were hospitalized for heart-related conditions, based on their positivity. During the study period, about half of all participants were hospitalized for a heart attack, heart failure or chest pain, for example, according to findings published in Circulation: Cardiovascular Quality and Outcomes.
The researchers said past studies also found a link between having a positive outlook and better heart health, but it was unclear what explained the association.
"There is some evidence to suggest that even among people who are already ill, who already have heart disease or diabetes or related conditions, that those people who are happier also have better outcomes," Julia Boehm from Chapman University in Orange, California, who has studied psychological wellbeing and heart health, said.
Health behaviors such as exercise are one possible explanation for that link, she told Reuters Health. Some researchers have also proposed another mechanism, suggesting optimism may affect physiologic processes in the body that would ultimately influence heart health, such as inflammation levels.
Pedersen and her colleagues noted that they did not have information on participants' type or intensity of exercise. The researcher also said the study can't say how exercise and positive affect may be linked.
"We do not know what comes first (also known as the ‘chicken and egg' problem) and thus cannot make any conclusions about the direction of causality - is it exercise that increases positive affect or positive affect that leads to more exercise with an effect on mortality or both?" Pedersen told Reuters Health in an email.
"Irrespectively, it cements what we already know - namely that exercise is good for the heart."
Boehm, who wasn't involved in the new research, said there isn't enough evidence to tell people with heart disease to be happier or more optimistic in order to improve their outcomes. But she agreed with Pedersen that there are data to support recommending exercise to those people for heart health.
"Hopefully you would have the added benefit of feeling more happy (and) optimistic," she said.