Ageing research has undergone a paradigm shift from descriptive theories to a mechanistic understanding grounded in the interconnected biological processes. This work synthesizes the current landscape of ageing research, emphasizing the critical role of biomarkers in translating mechanistic insights into clinical application. Biomarkers, ranging from molecular and cellular markers to functional and imaging parameters, serve as essential tools for quantifying biological age, assessing the efficacy of therapeutic interventions, and predicting age-related disease risk. However, rather than offering another catalogue of hallmarks or isolated biomarker classes, this work structures the field through a translational decision framework that connects mechanistically grounded, organ-specific biomarkers to therapeutic evidence levels, participant stratification, longitudinal response tracking, and safety evaluation. Within this framework, we distinguish interventions targeting ageing biology from those directed at established age-related diseases, critically assess insights from inconclusive or negative human trials, and delineate essential prerequisites for biomarker qualification and clinical adoption. Despite significant challenges, such as the lack of a universal gold standard biomarker and discrepancies between preclinical models and human biology, the continued development and validation of robust biomarker systems are imperative. As the field moves toward next-generation composite biomarkers and multi-target combination therapies, biomarkers will be indispensable for driving the paradigm shift from treating age-related diseases to proactively managing the ageing process itself, ultimately paving the way for clinical-grade anti-ageing interventions.
