MONDAY, March 5 (HealthDay News) -- Older people with heart disease who have undergone a cardiac catheterization may be at much greater risk for mental decline if they also show persistent signs of depression, according to a new study.

Researchers from the University of Calgary in Alberta, Canada, followed 350 patients aged 60 or older who had a nonemergency catheterization and found those who had persistent symptoms of depression experienced significantly greater mental decline 30 months after their procedure.

Being depressed within the first year after surgery was a significant risk factor for continued decline over the next 18 months. Lead researcher Elizabeth Freiheit and her colleagues found mental declines were most severe for people with a specific gene form -- the apolipoprotein E epsilon-4 allele -- which is believed to be a genetic risk factor for Alzheimer's disease.

For patients with heart disease, "these findings illustrate the need for longer-term monitoring of depressive-symptom severity and change by clinicians and other caregivers," the study authors said in a university news release.

The study will be published in the March issue of the Archives of General Psychiatry.

Although an association between depression and mental decline was seen in these patients, it does not necessarily confirm a cause-and-effect relationship.

More information

The U.S. National Institute of Mental Health provides more information on depression.