Aging biology and geriatric disease in dogs and cats

Importance: As companion animals live longer, veterinarians face an increasing prevalence of complex, multisystem diseases shaped by the biology of aging.This review synthesizes current evidence that aging is a biologic, not merely chronological, process, linking cellular and systemic hallmarks to organ-level pathology and clinical decision-making in dogs and cats.Observations: Our synthesis of over 350 peer-reviewed sources identified shared and species-specific patterns of age-associated disease across major organ systems.In both dogs and cats, genomic instability, telomere attrition, mitochondrial dysfunction, oxidative stress, and cellular senescence converge in systemic processes such as immunosenescence, inflammaging, sarcopenia, and frailty, which amplify multimorbidity risk.Organ-based analyses revealed differences in prevalence and progression of key conditions-such as myxomatous mitral valve disease and osteoarthritis in dogs, versus chronic kidney disease and hyperthyroidism in cats-while highlighting common pathways of tissue degeneration, metabolic dysregulation, and immune decline.Structured diagnostic-therapeutic tables demonstrate that integrating these mechanistic insights supports earlier screening, targeted intervention, and longitudinal monitoring.Notably, recognition of multimorbidity and frailty as central geriatric syndromes emerged as a recurring theme with direct implications for prognosis and care planning.Conclusions and Relevance: By aligning geroscience concepts with practical, speciesspecific clinical frameworks, this review provides veterinarians with tools to improve proactive screening, precision diagnosis, and individualized management in aging pets.Applying these findings may extend healthspan, mitigate functional decline, and enhance quality of life in senior and geriatric dogs and cats.