The period established aging as a systemic, multi-organ biology in which vascular, renal, neural, and immune processes interweave to shape health trajectories, integrating physiology, developmental biology, and longevity science to model aging as a coordinated body-wide phenomenon. Researchers foregrounded standardized assessment through biomarkers, sleep measures, renal function indices, creatinine clearance, cross-sectional and longitudinal aging metrics, and pharmacokinetic profiles to quantify aging rate and health status. Pharmacology and drug disposition in aging gained priority, guiding geriatrics-specific dosing, safety, and efficacy considerations while clinical care, public health, and disease patterns in older adults framed evolving policies and practice. Historical Significance: The era laid foundational concepts for modern geriatrics by unifying aging biology with functional status and care delivery. Foundational assessment tools expanded beyond basic activities of daily living to include instrumental activities of daily living, enabling disability research and elder care planning. Quick cognitive screening methodologies emerged, along with integrative perspectives on aging that connected biology, medicine, and social factors to policy and research priorities for longevity and elder care.