People who are socially active and mellow may be less likely to develop dementia, a new study finds.

Dementia is a loss of mental function, such as memory and reasoning, that is severe enough to interfere with everyday life. Several diseases can cause dementia, including Alzheimer's (the most common cause of dementia in the United States) and Parkinson's disease as well as nutritional deficiencies, stroke and infections that affect the brain.

About one in seven Americans aged 71 and older has some form of dementia, the study researchers say.

However, scientists have yet to pinpoint a single cause of dementia beyond the general associations with disease. While genes play a role in some kinds of dementia, dementia caused by Alzheimer's disease and some other disorders results from a combination of genes, lifestyle and other environmental factors, according to the National Institute of Neurological Disorders and Stroke. For instance, recently a team of scientists found that in mice the gene Bmi1 controls the normal and pathological aging of brain cells — a process that could lead to dementia.

The new study, which is detailed in the Jan. 20 issue of the journal Neurology, reveals personality traits and lifestyle could be major factors.

"The good news is, lifestyle factors can be modified as opposed to genetic factors which cannot be controlled," said study researcher Hui-Xin Wang of the Karolinska Institute in Stockholm, Sweden. "But these are early results, so how exactly mental attitude influences risk for dementia is not clear."

Personality and lifestyle

Wang and her colleagues followed more than 500 elderly people for six years. None of the individuals, with an average age of about 83, had dementia at the study's start. Over the study period, 144 developed dementia.

The participants completed questionnaires about their personality traits and lifestyle, including degree of neuroticism (how easily the person gets distressed), level of extroversion, amount of leisurely activities and the richness of their social networks.

A person scoring low on neuroticism was characterized as calm and self-satisfied, whereas those who were easily distressed (high neuroticism) tended to be emotionally unstable, negative and nervous.

Regarding personalities, outgoing individuals scored high on the extroversion scale and were more socially active and optimistic compared with individuals scoring low on extroversion.

Stop the stress

Results showed that among people who were socially isolated, those who were calm and relaxed were 50 percent less likely to develop dementia compared with individuals who were prone to distress. Also, among the outgoing extroverts, the dementia risk was also 50 percent lower for people who were calm compared with those who were prone to distress.

The researchers say the ability to handle stress without anxiety could help to explain the findings.

"In the past, studies have shown that chronic distress can affect parts of the brain, such as the hippocampus, possibly leading to dementia," Wang said, "but our findings suggest that having a calm and outgoing personality in combination with a socially active lifestyle may decrease the risk of developing dementia even further."

The study was supported by the Swedish Council for Working Life and Social Research, Alzheimer Foundation Sweden, Swedish Brain Power, Swedish Research Council, Gamla Tjänarinnor Foundation, Fredrik and Ingrid Thurings Foundation, Foundation for Geriatric Diseases and Loo and Hans Osterman Foundation for Geriatric Research at Karolinska Institute, and the Center for Health Care Science at Karolinska Institute.