Lonely individuals may be twice as likely to develop the type of dementia linked to Alzheimer's disease in late life as those who are not lonely, according to an article in the February issue of Archives of General Psychiatry, one of the JAMA/Archives journals.
Social isolation--characterized by a small social network, being unmarried and participating in few activities with others--has been linked to an increased risk for dementia, according to background information in the article. "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.
Robert S. Wilson, Ph.D., Rush University Medical Center, Chicago, and colleagues analyzed the association between loneliness and Alzheimer's disease in 823 individuals with an average age of 80.7. At the beginning of the study and every year after for up to four years, participants underwent evaluations that included questionnaires to assess loneliness, classifications of dementia and Alzheimer's disease, and testing of their thinking, learning and memory abilities. Loneliness was measured on a scale of one to five, with higher scores indicating more loneliness. The data were collected between November 2000 and May 2006.
At the first examination, participants' average loneliness score was 2.3. During the study period, 76 individuals developed dementia that met criteria for Alzheimer's disease. Risk for developing Alzheimer's disease increased approximately 51 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). The findings did not change significantly when the researchers factored in markers of social isolation, such as a small social network and infrequent social activities.
Autopsies were performed on 90 individuals who died during the study. Loneliness during life was not related to any of the hallmark brain changes associated with Alzheimer's disease, including nerve plaques and tangles, or tissue damaged by lack of blood flow. "The results suggest that loneliness may contribute to risk of an Alzheimer's disease-like dementia in late life and does so through some mechanism other than Alzheimer's disease pathology and cerebral infarction," or the cutoff of blood supply to the brain, the authors write.
The mechanism that does link dementia and loneliness is unclear; because loneliness levels remained relatively stable even in individuals who developed dementia, it seems unlikely that loneliness is caused by dementia, the authors 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 and, as a result, be less able to compensate for other neural systems compromised by age-related neuropathology. Further clinicopathologic and clinicoradiologic research is needed to investigate these and other possibilities."
(Arch Gen Psychiatry. 2007;64:234-240. Available pre-embargo to the media at www.jamamedia.org.)
Editor's Note: This study was supported by grants from the National Institute on Aging and by the Illinois Department of Public Health. Please see the article for additional information, including other authors, author contributions and affiliations, financial disclosures, funding and support, etc.