Dr. Lester Breslow, a public health leader whose research gave mathematical proof to the notion that people can live longer and healthier by changing habits like smoking, diet and sleep, died Monday at his home in Los Angeles. He was 97.

The University of California, Los Angeles, where Dr. Breslow was a former dean of the Fielding School of Public Health, announced the death.

Dr. Breslow’s most lauded accomplishment was a study of 6,928 people in Alameda County, Calif., that examined their behavior over intervals of up to 20 years. It used quantitative analysis to prove that a 45-year-old with at least six of the seven healthy habits Dr. Breslow chose as important had a life expectancy 11 years longer than someone with three or fewer.

Over a 70-year career, Dr. Breslow helped expand the very definition of public health, from the historical concentration on communicable disease to a new concern with individual behavior and the effects of community and environment. As people lived longer and had more cancer and heart attacks, he was a leader in emphasizing the mounting importance of chronic disease.