Older people who have symptoms of depression are also more likely to develop heart disease and to have heart attacks and strokes, researchers said on Tuesday.

In a 10-year study of people aged 65 and older, researchers said they found those who had symptoms of depression, such as feeling fearful, irritable or unable to sleep, were 40 percent more likely to develop heart disease.

Maybe they are not eating right, or perhaps they feel too low to exercise. Or there could be an unknown physical factor that causes both depression and heart disease, the researchers reported in the journal Circulation, published by the American Heart Association.

The researchers did not look for clinical depression, but questioned 4,493 volunteers over the age of 65 about their symptoms. Most of the patients did not have diagnosed heart disease at the beginning of the study. They were followed for 10 years to see if they developed heart disease.

They were given a 90-minute home interview and asked about their health, medications, feelings of depression, irritability, worry, fear, and loneliness, and whether they had trouble focusing on daily activities.

"Those with higher scores reported that they felt 'down,' didn't sleep well, were unhappy or had little hope about the future," Dr. Curt Furberg, a professor of public health science at Wake Forest University in Winston-Salem, North Carolina, said in a statement.

"These are the typical symptoms of depression that many people have at times."

They were also given regular medical exams and doctors diagnosed heart disease, which included stroke, heart attack and heart arrhythmia but not high cholesterol or high blood pressure.

Other studies have found that between 19 and 30 percent of Americans over the age of 65 have symptoms of depression, but only 1 percent get treated for it.

DEPRESSION COULD LEAD TO UNHEALTHY HABITS

The researchers said that depressed people tend to exercise less, smoke more and eat less healthily + all of which raise the risk of heart disease. Mental stress may also cause the arteries to clog.

Also, depression may increase production of free radicals and fatty acids, which can damage the lining of blood vessels, Furberg said.

"There have been a number of studies that looked at changes in serotonin levels with depression, and worsening immune function in people who are more depressed," Mary Haan, an associate professor in epidemiology at the University of Michigan, who worked on the study, said in a telephone interview.

"But I don't think anybody has really got a complete handle on why this happens."

Several infections are linked with heart disease, so immune function could be key. Serotonin is an important message-carrying chemical linked with mood but it also has other physiological roles.

Haan said it is also possible that people become depressed because undiagnosed heart disease makes them feel poorly.

"A person who is developing cardiovascular disease has greater levels of atherosclerosis, poorer circulation in the brain. They feel badly without having a clinically diagnosed disease," Haan said.

"I think this may feed back on itself. A person who is not feeling as well starts feeling depressed and they modify their lifestyle and start to feel worse, so there is probably a kind of downward spiral."

Now it will be important to see if treating depression reduces the risk of heart disease, which kills half of all people in developed countries.

"The next step is whether treatment will stave off or slow the progression of heart disease," Furberg said. He said two such studies are being started.

Haan said drugs may not be necessary. "If people change their lifestyles because they are depressed, we could also be looking at non-pharmacological solutions such as exercise, social programmes and dietary interventions," she said.

(Chinadaily)