Staying active socially may help prevent Alzheimer's disease in the elderly, say US researchers.
Alzheimer's is a progressive brain disorder that gradually destroys a person's memory and ability to reason and make judgments.
David Bennett and other researchers from the Rush University Medical Center studied 823 people in and around Chicago with an average age of about 80, none of who had dementia at the start of the study, reported ABC online (Australia Broadcasting Corporation).
Over a four-year period, researchers asked the participants about their social activity - whether they felt they had enough friends, whether they felt abandoned or experienced a sense of emptiness.
They were given a score between 0 (least lonely) and 5 (most lonely).
Over four years, 76 people in the study developed Alzheimer's. Those who did were more likely to have poor social networks; the higher they scored, the greater the risk.
Those with a score of 3.2 or more (the loneliest 10 percent) had double the risk of those scoring below 1.4 (the least lonely 10 percent).
When researchers autopsied the brains of 90 people who died over the four-year period, they didn't find a correlation between their loneliness scores and any physical brain changes of Alzheimer's.
It seems that loneliness increases the chances of having Alzheimer's symptoms but not physical brain changes.
How loneliness increases the risk of Alzheimer's, the researchers weren't able to say. But there have been other studies that link social isolation with mental decline, and an increased risk of dementia.