Abstract / Summary
Abstract Background Isolated or lonely older adults are more likely to become disabled; whether these exposures shape the direction of functional change — deterioration versus recovery — in cardiometabolic multimorbidity (CMM) is unknown. We examined how the two exposures relate to functional-state transitions and death in middle-aged and older adults with CMM. Methods We studied 1,731 adults aged ≥ 45 with CMM (≥ 2 of hypertension, dyslipidaemia, diabetes, heart disease or stroke) from waves 1–5 (2011–2020) of the China Health and Retirement Longitudinal Study. Isolation was a four-item index (unpartnered, living alone, no weekly child contact, no social activity); loneliness came from the Center for Epidemiologic Studies Depression Scale (CES-D) item. Crossed, they defined four groups (G1 low isolation/no loneliness, G2 loneliness only, G3 isolation only, G4 both). Multistate Markov models estimated associations with nine transitions among independence, instrumental activities of daily living (IADL) limitation, activities of daily living (ADL) limitation and death. Results Over 9 years, 286 participants (16.5%) died. Loneliness was linked to deterioration onset (G2 vs G1: independence→IADL limitation hazard ratio [HR] 2.83, 95% confidence interval [CI] 1.09–7.31; independence→ADL limitation 2.01, 1.28–3.15). Dual exposure carried a distinct signature: faster early deterioration (1→2 HR 2.66, 1.62–4.37), 66% lower recovery from ADL limitation (3→1 0.34, 0.17–0.70) and higher post-disability mortality (3→4 1.57, 1.04–2.39). Expected years independent between ages 60–90 were 4.83 (G1) versus 0.65 (G4): a 4.18-year gap. Conclusions In CMM, loneliness acted mainly at deterioration onset; dual exposure was marked by lost recovery and excess post-disability mortality. Social connection may be a modifiable target for preserving function across CMM trajectories.