by Karin Modig, Marcus Ebeling A common misconception is that increasing longevity reflects slower aging. Instead, most longevity gain comes from medical advances that allow survival with disease, rather than changes to the biology of aging itself, challenging how we study aging and health. Modern medicine has transformed not only how long we live, but also how we age, with more people surviving to old age with chronic disease. This Perspective examines how aging, health, and care should be redefined to reflect these increasingly complex later lives.