Importance: The association of use of electronic nicotine delivery systems (ENDS) with the age of asthma onset is unknown.

Question: Is the use of electronic nicotine delivery systems (ENDS) in the past 30 days associated with the age of asthma onset among adults (≥18 years) and youths (12-17 years) who never used cigarettes?

Findings: This cohort study of 7766 adults and 17 023 youths from the Population Assessment of Tobacco and Health Study (2013-2021) found that adults who used ENDS in the past 30-days had an increased risk for asthma incidence at earlier ages vs adults who did not use ENDS in the past 30 days. This finding did not hold for youths.

Meaning: These findings suggest that tobacco regulations, prevention, intervention campaigns, and cessation programs are needed to prevent early age of asthma onset among adults who use ENDS, to protect public health, and to help improve asthma screening guidelines.