The heritability of social connections among older adults and their associations with mental and cognitive health: Older Australian Twins Study.

Abstract

Social connections might be protective against depressive and anxious symptoms and dementia in later life. The extent to which social connections are heritable versus modifiable in older age remains unknown. We aimed to investigate the heritability of social connections and their influence on mental and cognitive health over time among older adults in a longitudinal cohort. We analysed data from the Older Australian Twins Study (333 monozygotic, 266 dizygotic twins; 65+ years) at three time-points over 6 years. We examined the factor structure and heritability of baseline social connections and their associations with mental and cognitive health longitudinally. We found three weakly heritable social connections factors: (a) interacting with friends/neighbours/community (<i>h</i>² = 0.09, 95% CI: 0.00, 0.44); (b) family interactions/childcare (<i>h</i>² = 0.13, 95% CI: 0.00, 0.43); (c) involvement in religious groups/caregiving (<i>h</i>² = 0.00, 95% CI: 0.00, 0.19). Strong genetic correlations were observed between depressive symptoms and factors a (<i>r</i> = -0.96) and b (<i>r</i> = -0.60). More frequent baseline interactions with friends/neighbours/community were associated with fewer depressive symptoms cross-sectionally (<i>B</i> = -0.14, <i>p</i> = .004) and longitudinally (<i>B</i> = -0.09, <i>p</i> = 0.006), but the associations between social connections and cognitive health were not significant. Social connections were weakly heritable, suggesting large environmental determination. Connections with friends/neighbours/community were associated with better mental health cross-sectionally and over time.