The social cost of iron: brain iron in face-processing regions links lower face-perception performance to reduced social connectedness in aging.

Face perception is fundamental to social interaction yet declines in older individuals. The social implications and mechanisms of this decline remain unclear. Here, we tested whether face-perception performance of 35 healthy, older adults is related to social connectedness and assessed regional brain iron as a hypothetical underlying mechanism. Face and non-face perception was assessed with the Cambridge Face and Cambridge Car Memory Test. Social connectedness was indexed as a composite of the Duke Social Support Index, UCLA Loneliness Scale, and Lubben Social Network Scale. A discrimination task to localize face- and house- processing was completed with fMRI data acquisition, and quantitative susceptibility mapping to index brain iron load was collected. Iron load in face-processing regions—but not in control regions—was associated with poorer face, but not non-face, perception, and poorer face-perception was also associated with lower social connectedness. Mediation analyses supported a perceptual-social pathway in aging whereby regional brain iron relates to lower social connectedness via face perception.