IntroductionData on adverse childhood experiences (ACEs) are key to understanding their burden and informing prevention programs and strategies. Population-based surveys that collect ACEs data may be affected by item non-response. This study examines differences in non-response to the optional Behavior Risk Factor Surveillance System (BRFSS) ACEs module overall, by sociodemographic characteristics, year, and question. MethodsThe study used BRFSS ACEs Module data from 21 states in 2019 and 16 states in 2021. Weighted proportions and 95% confidence intervals (95% CI) of responders and non-responders to the ACEs module by year and sociodemographic characteristics, and percentages of non-responders for each question were calculated. Chi-square tests were used to assess statistically significant (p<0.05) differences. Analyses were conducted in 2023. ResultsIn 2019 and 2021, 1.2% (95% CI=1.1, 1.4) and 2.4% (95% CI=2.2, 2.5) of BRFSS participants were non-responders to the ACEs Module, respectively (p<0.01). Compared with responders, non-responders were more likely to be non-Hispanic Black (p=0.01) or non-Hispanic Asian (p=0.01), unemployed (p<0.01), have income <$15,000 (p<0.01), or report poor health (p<0.01). Non-response by question increased as the module progressed, and non-response was highest for sexual abuse questions. ConclusionsOverall, findings demonstrate that individuals are willing to respond to the ACEs module questions. Although low, non-response to the module increased from 2019 to 2021. Higher non-response for sexual abuse questions may be due to their sensitivity or potential survey fatigue due to placement at the end of the module. Higher non-response among racial/ethnic minorities and economically disadvantages groups highlight opportunities to improve existing surveillance systems.