That news comes from a new study in the Journal of the American College of Cardiology.
Based on the study's findings, doctors should monitor and try to ease heart disease patients' anxiety, note the researchers, who included cardiologist Charles M. Blatt, MD, FACC, of Harvard Medical School.
"Most patients come in very anxious about their coronary condition," Blatt says in an American College of Cardiology news release.
"I'm convinced that spending time with the patient and the family and interacting with them as a caring human being is critically important to clinical outcomes," Blatt says. "My hunch is that for the majority of patients, the greatest anxiety-reducing effect comes from having a good relationship with a doctor."
The patients were 68 years old, on average; roughly eight in 10 were men.
At the study's start and every year for up to five years, the patients completed a survey about how they had felt in the previous week, ranging from "peaceful" to "feeling that something bad will happen."
The survey also covered patients' recent sleep problems and upset stomachs.
Blatt's team followed the patients for about three years, on average. During that time, 19 patients died and 44 had nonfatal heart attacks.
The researchers calculated the patients' anxiety score on each survey, as well as their cumulative anxiety score from all of the annual surveys.
High Anxiety, Higher Risk
Patients with high cumulative levels of anxiety were 6% more likely to die or have a nonfatal heart attack during the follow-up period, compared to those with low cumulative levels of anxiety.
What mattered most was whether the patients became more anxious over the years or calmer as time passed.
That is, the patients' initial anxiety score wasn't a good predictor of their risk of death or heart attack. Their risk rose or fell in sync with their anxiety scores across the surveys.
However, the researchers say it's possible that other, unmeasured factors affected the results.
Future studies should test anxiety-reduction techniques in heart disease patients, note Blatt and colleagues.