Lonely people may have a greater risk of developing late-life dementia, researchers from Rush University Medical Center in Chicago reported this week.
The study of 823 people older than 80 found that those who described themselves as lonely were twice as likely to develop the kind of dementia associated with Alzheimer's disease.
Previous studies have suggested that people who are socially isolated or lack intellectual stimulation are at greater risk for Alzheimer's. The latest report, published Tuesday in Archives of General Psychiatry, was the first to link loneliness to late-life dementia.
The four-year study used questionnaires to assess loneliness, asking participants to grade their response to such statements as, "I miss having really good friends" and "I often feel abandoned." None of the participants had signs of dementia when the research began.
During the study, 76 people were diagnosed with Alzheimer's, which is marked by memory loss and confusion. The risk of dementia increased 51% for each 1-point increase on a 5-point loneliness scale, said lead author Robert S. Wilson of Rush.
Wilson said the study indicated someone could feel lonely even when there were people around.
The study gives clinicians another risk factor to look for in elderly patients, said Laurel Coleman, a geriatrician in Maine and spokeswoman for the Alzheimer's Assn. "It made me think that I should not just ask patients about their social network, but also about their perception of being lonely," she said.
Wilson said no one understood why loneliness was linked to dementia.
Autopsies performed on lonely people with dementia as part of the study revealed no signs of stroke or Alzheimer's disease, Wilson said. More study was needed to find out how loneliness might change the workings of brain, he said.
But Dr. Gary W. Small, director of the UCLA Center on Aging, said it was possible that intense loneliness was the result of changes in the brain and not the cause. The study "doesn't really give us the answer," he said.