Longitudinal data is information collected about the same patient, group, or subject at multiple points over time. In healthcare, it can include clinical measurements, diagnoses, treatments, and outcomes, allowing researchers and care teams to study changes rather than rely on a single snapshot.
Because these records can reveal sensitive health patterns, their use requires strong governance and security. Organizations should control access with least privilege, track queries in audit logs, and preserve data provenance so its origin and handling remain traceable. When records are shared across research or business partners, clear permissions and purpose limits help prevent access or reuse beyond what is authorized.