Valid and Invalid Accelerometry Data Among Children and Adolescents: Comparison Across Demographic, Behavioral, and Biological Variables

Abstract Purpose. To examine whether there are differences between demographic, behavioral, and biological variables for those with invalid accelerometry data (IAD) and those with valid accelerometry data (VAD). Design. Cross-sectional. Setting. Data from 2003–2006 National Health and Nutrition Examination Survey (NHANES) were used. Subjects. Participants included 1,315 children (i.e., 6–11 years) with VAD and 534 children with IAD and 1,859 adolescents (i.e., 12–17 years) with VAD and 1,057 with IAD. Measures. Physical activity (PA) was measured using an accelerometer, with questionnaires used to assess demographic and behavioral variables and biological parameters assessed from a blood sample. Analysis. Wald and design-based likelihood ratio tests and logistic regression were used to assess differences between those subjects with IAD and those with VAD. Results. After adjustments, overweight children, compared to normal weight children, were 1.6 (odds ratio [OR] = 1.67; 95% confidence interval [CI]: 1.2...