-LRB- CNN -RRB- -- People with a stable mood and better capacity to handle stressful situations without anxiety have a reduced risk of developing dementia , according to a study published this week in the journal Neurology . Stress can increase the risk of dementia in older people , a study has found . This finding was particularly strong in highly extroverted people , the study said . Subjects who were both socially active and not easily stressed had the lowest risk for dementia . But even socially isolated individuals who were more calm and self-satisfied showed a reduced likelihood of dementia , the study said . Extroverted people usually have more optimistic outlooks on life , and `` may be better equipped to cope with stressful events and therefore less prone to depression , '' said Hui-Xin Wang of the Karolinska Institute in Stockholm , Sweden , and lead author of the study . The study looked at 506 older people from the Kungsholmen Project in Stockholm who did not have dementia at the first examination . These people then filled out questionnaires that determined their personality types and level of social activity . Those who said they were easily distressed were classified as having high neuroticism . Researchers followed these participants for six years , during which time 144 of them developed dementia . Although it is not easy to change someone 's personality , `` The good news of our finding is that an active lifestyle -- having a rich social network and participating in physical , mental and social activities -- may buffer the negative effect of high neuroticism on dementia risk , '' Wang said . One in seven Americans age 71 and older , or about 3.4 million , have dementia , according to the National Institutes of Health . In this age-group , 2.4 million people have Alzheimer 's disease , NIH research has shown . Alzheimer 's disease is the most common cause of dementia , according to the Mayo Clinic . Previous research has documented that personality factors may play a role in how people cope with dementia . This study is unique in that it looks at a combination of different lifestyle and personality traits , said Dr. Yaakov Stern , professor of clinical neurology at Columbia University Medical Center , who was not involved with the study . Stern and colleagues have found that people with higher educational or occupational attainment , or who engage in leisure activities , appear less demented . They call this concept `` cognitive reserve , '' because these lifestyle factors seem to allow them to cope with the pathology of the disease better . That is , as the disease progresses in the brain , those who have a greater `` reserve '' do not show symptoms of Alzheimer 's -- memory loss and impairment of day-to-day functions -- as quickly . Mounting evidence suggests that lifestyle factors also directly influence brain changes , he said . The Swedish study builds off the established idea in the field that stress actually harms the brain . The pathology of dementia appears about 10 to 15 years before a person actually develops Alzheimer 's disease , Stern said . That means , just like a man with prostate cancer may not have any symptoms , a person 's brain may have undergone changes that lead to Alzheimer 's without visibly affecting a person 's day-to-day life . Doctors can look for indications of the disease using positron emission tomography -LRB- PET -RRB- scans . A chemical called Pittsburgh Compound B is used in the imaging of brain tissues to find signatures of Alzheimer 's -- namely , beta-amyloid plaques and neurofibrillary tangles . `` The working idea is that if we can detect it before it 's clinically expressed and stop it then , we can prevent people from developing the disease , '' Stern said .