Abstract P323: Youth Characteristics Related to Participation in Accelerometer-Measured Physical Activity

Introduction: Accelerometer-measured physical activity is considered the ‘gold standard’ of physical activity (PA) measurement. However, previous studies have found that adults in accelerometer studies are more likely to be male, healthier and employed. Little is known about the correlates of participation among youth. We assessed characteristics associated with participation in accelerometer-measured PA among a cohort of healthy Chilean adolescents. Methods: Participants were 670 youth from an ongoing observational study who have been studied since infancy. The adolescent follow-up included measurement of PA with a hip-accelerometer worn for ≥10 hrs/day for ≥5 days or ≥3000 min over a 4-day period. We used multinomial logistic regression to evaluate socioeconomic, lifestyle, and cardiometabolic factors associated with providing sufficient accelerometry data (“Completers”), insufficient data (“Incompleters”), and not participating (“Non-participants”) in adolescence. Results: The study sample was 47% female and 17 years of age. About 33% (n=223) were Completers, 10% (n=68) were Incompleters, and 57% (n=379) were Non-participants. Completers reported lower neighborhood crime, 50% less cigarette and alcohol use, had healthier diets, healthier cholesterol, and mothers with higher IQs compared to the other two groups (all p Conclusions: Participants providing complete accelerometer data were not representative of the full sample; they had healthier behaviors and perceived less neighborhood crime. There may be additional unmeasured variables, such as attitudes towards the wearable device, that contributed to participation. Selective participation in studies using accelerometry inhibits generalizability and threatens internal validity when analyzing PA as a predictor of cardiometabolic outcomes. More effort is needed in the design of studies to reduce incomplete and refused participation in accelerometry.