A Genetically Informed Longitudinal Study of Loneliness and Dementia Risk in Older Adults

Abstract

Although several studies have shown small longitudinal associations between baseline loneliness and subsequent dementia risk, studies rarely test whether change in loneliness predicts dementia risk. Furthermore, as both increase with advancing age, genetic and environmental selection processes may confound the putative causal association between loneliness and dementia risk. We used a sample of 2,476 individual twins from three longitudinal twin studies of aging in the Swedish Twin Registry to test the hypothesis that greater positive change in loneliness predicts greater dementia risk. We then used a sample of 1,632 pairs of twins to evaluate the hypothesis that effects of change in loneliness on dementia risk would remain after adjusting for effects of genetic and environmental variance. Phenotypic model results suggest that mild levels of baseline loneliness predict greater dementia risk. Contrary to our hypothesis, change in loneliness did not correlate with dementia risk, regardless of whether genetic and environmental selection confounds were taken into account. Worsening loneliness with age may not confer greater dementia risk.

Do We Become More Lonely With Age? A Coordinated Data Analysis of Nine Longitudinal Studies

“…In LISS, a propensity-score-matched study of loneliness change found that loneliness did not change in this particular sample (Buecker et al, 2021). In Octo-Twin and SATSA, it was found that loneliness follows a U -shaped curve, swinging up after age 60 (Kim et al, 2021; Phillips et al, 2022). In SHARE, late-life loneliness was related to educational and family factors, but loneliness trajectories were not formally tested (Fernández-Carro & Gumà Lao, 2022).…”

The Impact of Loneliness and Social Isolation on Cognitive Aging: A Narrative Review

“…Notably, the initial data collection for the analysis was conducted from 2010–2014, and represents a pre-pandemic experience, however, the levels of loneliness and social isolation reported in the study also vary greatly from the national average at the time. Similarly, a genetically informed longitudinal study also failed to establish a link between loneliness and dementia risk in older adults [ 68 ]. The study comprised of 1,632 pairs of twins from the Swedish Twin Registry who participated in one of the three previous longitudinal studies.…”

Correlations between Dementia and Loneliness

“…There are two hypotheses—the social causation hypothesis states that loneliness itself increases the risk of dementia, whereas under the social selection hypothesis the risk of dementia among lonelier people is more likely to occur because of their greater underlying biological and environmental risk exposure. For instance, in pairs of monozygotic twins, differences in the effect of loneliness on dementia risk should be attributed to the twins’ dissimilarity in environmental exposure, as they share all of their genotypes and common environments [ 20 ].…”