Chair-Rise Difficulty as a Functional Correlate in the Longitudinal Association Between Loneliness and Incident Osteoarthritis in Older Adults

Objective To examine whether chair-rise difficulty functions as a functional mediator in the association between loneliness/social isolation and incident osteoarthritis (OA). Methods Data from 6,232 adults ≥50 in 12 European countries (SHARE waves 7–9, 2017–2022). Social isolation and loneliness were exposures; depression, physical inactivity, and chair-rise difficulty were mediators; OA onset was the outcome. Structural equation modeling tested mediation, adjusting for covariates. Results No direct associations were found; both exposures had significant indirect effects via depression and functional decline. Chair-rise difficulty was the strongest mediator (β = 0.74, p < 0.001), followed by depression (β = 0.04, p = 0.033). Physical inactivity acted indirectly through chair-rise difficulty (β = 0.26, p < 0.001). Female sex and older-age independently increased OA incidence. Conclusion Loneliness and social isolation were indirectly linked to incident OA via psychological, behavioral, and functional mechanisms. Chair-rise difficulty is a functional intermediary linking psychosocial distress to physical vulnerability and increased OA incidence, not a direct cause of joint-degeneration.