THURSDAY, July 21 (HealthDay News) -- The more optimistic you are, the lower your risk of having a stroke, a new study suggests.

"Optimism protects against stroke," said researcher Eric Kim, a doctoral student at the University of Michigan. While it is not cause-and-effect link, Kim and his colleagues did find a significant association.

The finding is published in the July 21 online issue of Stroke.

The possible stroke protection lengthens the list of health benefits tied to being optimistic, Kim said. Already, various studies have found more optimistic people have a healthier immune system, faster wound healing, a lower risk of heart disease and other benefits, he said.

For the new study, Kim and his colleagues looked at data from the Health and Retirement Study. This is a nationally representative sample of U.S. adults over the age of 50.

The team looked at the results of standard optimism tests for 6,044 men and women. All were free of stroke at the study's start. The optimism score was on a 16-point scale. The participants self-rated their health, and the team followed them for two years. During the follow-up period, 88 cases of stroke occurred.

After adjusting for age, each unit increase in their optimism score reduced stroke risk about 9 percent, Kim said.

The researchers also adjusted for other factors such as smoking, alcohol use, race, gender, marital status, blood pressure, chronic illness, mental illness, body mass index and level of physical activity. They found the association between optimism and reduced risk of stroke remained robust.

How to explain the association? One possibility is that those who expect the best things in life take steps to promote their health, Kim said.

Another possibility is a biological effect, he said. "In a similar way that depression can impact functioning, we think optimism can as well," he said.

A different study by Finnish researchers found a link between low pessimism and reduced risk of stroke, but not between optimism and stroke. Kim hopes to continue his research, including a focus on what drives the link between optimism and reduced risk of stroke.

The study was partially funded by the Robert Wood Johnson Foundation's Pioneer Portfolio through the Positive Psychology Center at the University of Pennsylvania.

Dr. Martin Seligman, who directs the center and is a long-time optimism researcher, calls the new finding ''a major new discovery."

Optimism has previously been linked to protection against heart attacks, he said.

"Since optimism is teachable, this implies that a trial that teaches optimism to pessimists at risk for stroke might be of real benefit to public health," he said.

Another expert, Hermann Nabi, of the French National Institute of Health & Medical Research, has studied pessimism and stroke risk.

He called the results interesting but also noted some limitations, such as the self-reported stroke history and the limited follow-up. Even so, he terms the new findings "an important contribution to this line of research."

Optimism can definitely be learned, Kim noted.

How to define optimism? "Optimism isn't just the lack of anxiety or depression," Kim said. Someone who seeks help for either anxiety or depression might be lifted from a negative 10 or so on a scale back to zero, or neutral, he said.

"Optimism can bring you back to positive numbers," he said.

More information

To take a test on how optimistic you are, visit Stanford University.