Close up image of a caretaker helping older woman walk

Dr. Robert Butler, founding director of the National Institute of Aging and a lifelong seniors’ health advocate, died Sunday from complications due to acute leukemia. He was 83.

Over the course of his career, Butler helped found the American Association for Geriatric Psychiatry, the Alzheimer’s Disease Association and the International Longevity Center, according to his obituary in The New York Times. Many credit him with creating the medical field of geriatrics. He is also credited with coining the term “ageism.” In 1975, Butler wrote a book, “Why Survive? Being Old in America,” which earned him a Pulitzer Prize.

In a statement, Health and Human Services Secretary Kathleen Sebelius paid tribute to him.

“For his trailblazing work to help seniors live rich and healthy lives—to not just survive, but thrive—all Americans, young and old, owe him an enormous debt,” she said.