Loneliness exacerbates age differences in the -allostatic-interoceptive system during induced affect.

Loneliness is associated with age-related health issues through its impact on the brain and body. The brain's allostatic-interoceptive system (AIS) consists of regions that predictively regulate bodily functions in reaction to affectively or socially salient situations. We hypothesized that loneliness would interact with age to exacerbate normative age-related differences in the static (i.e. average) and dynamic (i.e. time-varying) functional connectivity of the AIS during socially salient scenarios. Participants (N = 73) rated their loneliness and underwent functional magnetic resonance imaging (fMRI) during a task involving socially neutral, pleasant, and unpleasant conditions. Static and dynamic functional connectivity of the AIS were each quantified using participation coefficient (PC) and within-module degree (WD), which are graph-theoretical metrics indicating integration of the AIS with the rest of the brain and coherence within itself, respectively. Static AIS PC was positively associated with age across conditions. In the socially pleasant condition, static AIS WD decreased with increasing age, but only for those with high loneliness. In both the pleasant and unpleasant conditions, dynamic PC and WD showed steeper negative associations with age in individuals with higher loneliness. Overall, loneliness may exacerbate age-related differences in brain systems that are essential for physiological regulation and responding to social cues.