Importance: The benefits of smoking cessation are well known, but former smokers have a higher health risk than never smokers. The impact of former smokers' engaging in other aspects of a healthy lifestyle is unclear.

Question: Are healthy lifestyle choices associated with reduced mortality among former smokers?

Findings: In this cohort study of 159 937 former smokers in the National Institutes of Health–AARP Diet and Health Study, former smokers who reported the highest adherence to recommendations for body weight, diet, physical activity, and alcohol intake had a 27% lower risk of all-cause mortality compared with those who reported the lowest adherence. Associations were also observed for deaths from cancer, cardiovascular disease, and respiratory disease.

Meaning: These findings suggest that former smokers may additionally lower their risk of premature death by adhering to healthy lifestyle recommendations.