Associations of sarcopenia with depression and suicidal ideation: the sex-specific mediating role of loneliness

The global aging population amplifies sarcopenia’s burden, a syndrome linked to physical decline and comorbid mental health risks. Despite growing understanding of the associations between sarcopenia, depression, and suicidal ideation, the mediating role of loneliness and sex-specific patterns remains underexplored. This study investigates whether loneliness mediates the sarcopenia–negative mood relationship and examines sex differences in these pathways among Hong Kong older adults. We analyzed data from 2,126 adults aged ≥ 60 (69 ± 6.5 years, 57% women) in the 2024–2025 Panel study of Active Ageing and Society (PAAS). Sarcopenia was assessed using the SARC-F questionnaire (score > 4). Negative mood included depressive symptoms (CES-D-8 scale) and past-week suicidal ideation (binary item). Loneliness was measured via a 3-item UCLA-based scale (score 3–9). Linear regression (depression) and probit models (suicidal ideation) tested associations, adjusted for sociodemographic and health covariates. Entropy balancing and propensity score matching were used to address selection bias. KHB decomposition analysis quantified the total, direct and indirect effects of the loneliness mediation, stratified by sex. Sarcopenia prevalence was 9.6%, disproportionately affecting women, socioeconomically disadvantaged adults, and patients with comorbidities. Adjusted models revealed sarcopenia was positively associated with depressive symptoms (B = 3.41, SE = 0.28) and a 17.6% greater probability of suicidal ideation (B = 0.83, SE = 0.11). Effects were stronger in women (depression: B = 3.48 vs. 3.11 in men). Loneliness mediated 23.73% of the sarcopenia–suicidal ideation association and 20.54% of the sarcopenia–depression association. Sex-dimorphic pathways emerged: loneliness mediated more of sarcopenia’s effect on suicidal ideation in men (27.98%) than women (22.48%), despite women’s stronger direct effects. Loneliness significantly explains the sarcopenia–mental health relationship, with men exhibiting stronger indirect pathways via loneliness. This highlights the need for integrated interventions targeting sarcopenia (e.g., resistance training) and loneliness (e.g., group-based social activities), tailored to sex-specific mechanisms. Scaling such approaches is urgent for the aging society, with highly prevalent sarcopenia and mental health problems among older adults.