February 12, 2007
People who feel lonely may be twice as likely to develop Alzheimer's disease in their later years as those who feel they have a close network of friends and family, researchers report. The findings appeared in the Archives of General Psychiatry, a mental health journal from the American Medical Association.
Earlier research has linked social isolation to an increased risk for dementia. People with a limited social network, those who do not get married, and individuals who participate in few activities with others all appear to be at higher risk for dementia.
"In contrast, little is known about the association of dementia with emotional isolation, or loneliness, which refers to perceived social isolation and feeling disconnected from others that is, to dissatisfaction with social interactions, rather than their absence," the authors write.
Study leader Dr. Robert S. Wilson, from Rush University Medical Center in Chicago, and colleagues analyzed the association between loneliness and Alzheimer's disease in 823 seniors (average age of 80). At the start of the study, all the participants filled out questionnaires to assess feelings of loneliness. They filled out similar surveys two years later, and again two years after that. Loneliness was measured on a scale of one to five, with higher scores indicating a greater degree of loneliness. Those in the study also underwent extensive testing for problems with thinking, learning, and memory, symptoms that might indicate the presence of Alzheimer's disease.
At the first examination, participants' average loneliness score was 2.3. During the study period, 76 of the seniors were given a diagnosis of Alzheimer's disease. The risk for developing Alzheimer's disease increased by over 50 percent for each point on the loneliness score, so that a person with a high loneliness score (3.2) had about 2.1 times the risk of developing Alzheimer's disease than a person with a low score (1.4). Feeling lonely was linked to a higher Alzheimer's risk, even after researchers considered such factors as a small social network and infrequent social activities.
Autopsies were performed on 90 seniors who died during the study. Curiously, feeling lonely during life was not related to any of the hallmark brain changes associated with Alzheimer's disease, such as plaques and tangles or other damage in the brain.
Scientists are unsure why or how loneliness may be linked to dementia. Because loneliness levels remained relatively stable during the course of the study, even in people who were diagnosed with Alzheimer's, it seems unlikely that loneliness is caused by dementia, the researchers note.
"In human beings, loneliness has been associated with impaired social skills," they write. "Thus, neural systems underlying social behavior might be less elaborated in lonely persons." As a result, they speculate, the brains of lonely people may be less able to compensate for the onslaughts of a disease like Alzheimer's.
Still, this does not rule out the possibility that individuals who experience the early stages of cognitive decline may become lonely due to the isolating effects of mental decline. The authors of the study call for further research to investigate these and other possibilities.
Alzheimer's is a complex disease that likely has a variety of causes. The genes you inherit, advancing age, exercise habits, the foods you eat, and myriad other factors may all influence who develops Alzheimer's in old age, and who remains mentally sharp and alert. The Fisher Center for Alzheimer's Research Foundation continues to fund critical research into the underlying causes of Alzheimer's, care of the disease, and the search for a cure. To learn more, visit www.ALZinfo.org, The Alzheimer's Information Site.
Robert S. Wilson, PhD; Kristin R. Krueger, PhD; Steven E. Arnold, MD, et al: "Loneliness and Risk of Alzheimer Disease." Archives of General Psychiatry, Volume 64, February 2007, pages 234-240.