Relationships between sedentary behaviour, physical activity levelsand red blood cell distribution width in children and adolescents

Background: Red blood cell distribution width (RDW) is a biomarker for cardiovascular disease(CVD). RDW is associated with sedentary behavior (SB) and physical activity (PA) in adults.To date, no study has evaluated this association in children. The purpose of this study was to evaluate the association between RDW and SB and PA levels of children and adolescents. Methods: This observational study included data from participants aged 12-20 years in the 2003–2006 National Health and Nutrition Examination Survey (NHANES). SB and PA were measured using accelerometers. Activity levels were classified into intensity categories. Sex specific multivariable regression analyses (adjusted for covariates) were used to explore the associations between SB, PA and RDW. Results: The study included 2143 children and adolescents (1080 boys and 1063 girls). In the fully adjusted regression model for boys, SB was positively associated with RDW (β =0.116,P=0.004) while moderate PA was negatively associated with RDW (β =-0.082, P=0.048). In girls, there were no significant associations between activity levels and RDW. Conclusion: This study provides preliminary evidence of the association between SB, moderate intensity PA and RDW in boys, but not in girls. Further research to determine the mechanisms associated with this relationship and underlying sex differences is warranted.