Is osteoporosis a driver or a passenger? Rethinking its role in age-related multimorbidity

Background Osteoporosis (OP) has traditionally been regarded as an age-related skeletal disorder characterized by bone loss and increased fracture risk. However, accumulating evidence suggests that OP is not merely a downstream manifestation of aging but may participate in systemic pathophysiological processes that extend beyond the skeleton. Conceptual Framework This review summarizes current evidence on the bidirectional interactions between OP and major aging-related disorders, including Alzheimer’s disease (AD), cardiovascular disease, and metabolic dysfunction. We propose the concept of the “bone–organ axis”, highlighting interconnected pathways mediated by chronic inflammation, endocrine signaling, metabolic regulation, and neurohormonal mechanisms. Within this framework, specific axes, such as the bone–brain and bone–cardiovascular axes, are discussed as representative models of cross-organ communication. Implications Reframing OP as both a consequence and a potential contributor to geriatric multimorbidity provides new perspectives for mechanistic investigation and clinical management. Future priorities include longitudinal studies to clarify causal directionality, identification of early cross-organ biomarkers, and development of integrated intervention strategies targeting shared molecular pathways.