TUESDAY, Feb. 6 (HealthDay News) -- Being lonely may increase the risk of developing Alzheimer's disease later in life, new research suggests.

Researchers at the Rush University Medical Center in Chicago assessed loneliness and dementia in 823 people, averaging almost 81 years of age, for up to four years. At the start of the study, the participants' overall average loneliness score was 2.3 on a scale from 1 (lowest) to 5.

Seventy-six people developed Alzheimer's disease during the course of the study, which is published in the February issue of the journal Archives of General Psychiatry.

According to the researchers, each point of increase on the loneliness score was associated with about a 51 percent increased risk of developing Alzheimer's.

This would mean that a person with a high loneliness score (3.2) would be about 2.1 times more likely to develop Alzheimer's than someone with a low score (1.4), they said.

Autopsies performed on 90 people who died during the study revealed that loneliness in life was not related to any of the characteristic brain changes -- such as nerve plaques and tangles -- that are associated with Alzheimer's disease.

So, the actual mechanism linking loneliness and Alzheimer's is unclear, the researchers said. It's unlikely that Alzheimer's actually causes the loneliness, they said.

"In human beings, loneliness has been associated with impaired social skills. Thus, neural systems underlying social behavior might be less elaborated in lonely persons and, as a result, be less able to compensate for other neural systems compromised by age-related neuropathy," the study authors wrote.

More information

The U.S. National Institute on Aging has more about Alzheimer's disease.