Social isolation increased the risk for incident dementia among older adults in the United States, according to study findings published in the Journal of the American Geriatrics Society.
The concept of social isolation refers to factors such as social connections, social support, resource sharing, and relationship strain. In the US, social isolation affects an estimated 1 in 4 older adults. Although previous research has pointed to a link between older adults who are socially isolated and a higher dementia risk, no study has described this longitudinal association in a nationally representative cohort of older adults in the US, according to researchers of the current study. They aimed to determine the relationship between social isolation and incident dementia over a 9-year period.
Researchers at Johns Hopkins University conducted a longitudinal, national cohort study from 2011 to 2020. They obtained data from the National Health and Aging Trends Study (NHATS) on 5022 community-dwelling Medicare beneficiaries (57.21% women; 71.71% White; mean age, 76.4 years; 42.4% with more than a college education).
NHATS includes domains related to the characterization of social isolation. These domains included living arrangements, discussion networks, and participation. In NHATS, social isolation was characterized by asking questions about living with at least 1 other person, talking to 2 or more people about “important matters” in the past year, attending religious services in the past month, and participating in clubs, meetings, or group activities, or volunteer work in the past month.
The participants received 1 point for each item/domain. A sum score of 0 or 1 was classified as “socially isolated” and those with sum scores of 2 or more were considered “not socially isolated.” Participants were classified as having probable dementia based on self-report, cognitive test performance <1.5 standard deviation below the mean of self respondents in 2 or more cognitive domains, and a score indicating probable dementia on the AD8 Dementia Screening Interview.
Of the 5022 Medicare beneficiaries, 1172 (23.3%) classified as socially isolated, while the remaining 3850 (76.7%) were not. During the 9-year follow-up period, 1060 (21.1%) of these older adults developed incident dementia.
After adjusting for certain demographic factors, the researchers discovered that socially isolated older adults demonstrated an increased likelihood of developing incident dementia compared with those who were not socially isolated (25.9% vs. 19.6%; hazard ratio [HR], 1.33; 95% CI, 1.13-1.56; P <.001). This trend associating social isolation with increasing rates of incident dementia continued even after the researchers adjusted for potential contributing health factors (HR, 1.27; 95% CI, 1.08-1.49; P <.01).
Social isolation increased dementia risk across all racial and ethnic groups without a significant difference between groups. A total of 18% of participants died prior to dementia over follow-up. The cause-specific HR of death before dementia associated with social isolation was 1.28 (95% CI, 1.12-1.47).
The researchers also estimated the cause-specific hazard of death before dementia.
The researchers’ findings highlighted that social isolation is associated with a greater risk for dementia among older adults. They concluded, “Elucidating the pathway by which social isolation impacts dementia may offer meaningful insights for the development of novel solutions to prevent or ameliorate dementia across diverse racial and ethnic groups,” they concluded.
Study limitations included attrition rate (30%) and the number of individuals (<1%) who transitioned from community dwelling into residential or nursing home care and the lack of assessment of other factors influencing social isolation, such as social support, loneliness, and relationship quality. Additionally, these results may be underestimated and not generalizable to noncommunity dwelling older adults since rates of social isolation and dementia are more prevalent within this particular population.
Huang AR, Roth DL, Cidav T, et al. Social isolation and 9-year dementia risk in community-dwelling Medicare beneficiaries in the United States. J Am Geriatr Soc. Published online January 11, 2023. doi:10.1111/jgs.18140