Oct. 29 (UPI) -- Loneliness increases a person's risk of dementia by 40 percent, according to a data analysis of 12,030 participants over 10 years.
Researchers at the Florida State University College of Medicine found the risk applies to all demographics, including gender, race, ethnicity or education, as well as whether there is social contact with friends and family. The findings were published Friday in the Journals of Gerontology.
"We are not the first people to show that loneliness is associated with increased risk of dementia," Dr. Angelina Sutin, an associate professor in FSU's Department of Behavioral Sciences and Social Medicine and principal investigator on the study, said in a press release. "But this is by far the largest sample yet, with a long follow-up. And the population was more diverse."
The researchers studied data on more than 12,000 participants collected as part of the University of Michigan's Health and Retirement Study of Americans 50 and older, and their spouses, sponsored by the National Institute on Aging and the Social Security Administration.
Participants explained their loneliness and social isolation, and were administered a cognitive battery every two years up to 10 years after their reports of loneliness. In the study, 1,104 people developed dementia.
"I think this study adds to the literature highlighting the importance of psychological factors and how individuals subjectively interpret their own situation," Sutin said. "That's equally important and separate from what we objectively measure. It also lends credibility to the idea of asking people how they feel about things -- in this case, how they feel about their social interactions."
People who feel lonely are likely to have several risk factors for dementia, the researchers said, including diabetes, hypertension and depression. In addition, they are likely to be physically active and more likely to smoke. Loneliness still predicted dementia even after adjusting for those risk.
The researchers defined loneliness as the "the subjective experience of social isolation." This is separate from actual social isolation.
"It's a feeling that you do not fit in or do not belong with the people around you," Sutin said. "You can have somebody who lives alone, who doesn't have very much contact with people, but has enough -- and that fills their internal need for socializing. So even though objectively you might think that person is socially isolated, they don't feel lonely."
Conversely, she said a lot of people can be socially engaged and interactive, and still feel like they don't belong. "From the outside it looks like you have great social engagement, but the subjective feeling is that you're not part of the group," Sutin said.
She believes people shouldn't been blamed for feelings of loneliness.
"People might say, 'You're lonely. Go make a friend,'" she said. "But it's not that easy."
Sutin said loneliness can have specific physical effects, including higher or longer-lasting inflammation, which can have other negative effects on health, behaviors such as heavy drinking or being sedentary that can damage the brain, and a lack of meaningful interaction that can lead to cognitive health problems.
"Loneliness is a modifiable risk factor," Sutin said. "Most people might describe periods where they felt lonely and then periods where they didn't feel lonely. So just because you feel lonely now, you don't always have to feel this way."