Physical Activity and Healthy Ageing & Longevity Data: Interoperability, Reuse, and Innovation in a Federated European Context

Background Physical activity (PA) is a cornerstone of Healthy Ageing and Longevity (HAL) and a high-leverage target for prevention-oriented health systems. Despite major advances in sensing technologies and digital health, PA and HAL research in Europe remains constrained by weak cross-study discoverability and limited data reuse. The bottleneck is not data scarcity but the absence of consistent cataloguing, taxonomies, and machine-actionable metadata enabling interoperability, federated analytics, and reproducible evidence synthesis. European policy initiatives emphasise secondary use of health data, real-world evidence (RWE), and AI-enabled analytics as key drivers of innovation within a federation-first governance model. Methods This article presents a conceptual and policy-facing analysis structured around a six-layer interoperability stack — cataloguing, metadata, semantics, provenance, access/governance, and computability — applied to current PA/HAL data practices in Europe. A present-situation analysis, gap analysis, and alignment agenda are situated within the EU’s evolving data governance landscape, including the European Health Data Space (EHDS) and the European Open Science Cloud (EOSC). Results PA/HAL data practices exhibit systematic gaps across all interoperability layers. Generic cataloguing fails to capture domain-relevant characteristics; metadata inconsistency undermines comparability; semantic fragmentation prevents federated analytics; and governance metadata is rarely machine-actionable. Knowledge graph-based semantic layers, combined with BBMRI-ERIC and ELIXIR infrastructures, represent underutilised bridges for domain-coherent discovery and reuse. Conclusions An alignment agenda for EHDS-compatible and Open Science -ready PA/HAL data is feasible using existing European components. Success depends on coherent assembly of cataloguing standards, shared taxonomies, machine-actionable provenance, and operational governance — not on centralisation. PA/HAL data represent a critical stress test for European data strategy: their effective reuse will depend on whether heterogeneous, context-sensitive data can be made meaningfully interoperable within a federated system.