Self-reported Versus Objectively Measured Physical Activity & Cardiometabolic Biomarkers Among Youth in NHANES

Purpose To compare associations between objective and subjective measures of moderate to vigorous physical activity (MVPA) & cardiometabolic biomarkers.

Methods 2174 (1110 boys) youth (12-19 years) from the 2003-6 NHANES combined surveys with self-reported MVPA (SRMVPA) in the previous 30 days & four 10-hour days of accelerometry MVPA (AMVPA) (Actigraph 7164) were included. The biomarkers were: body mass index (BMI, kg/m²), BMI percentile, height (cm), waist circumference (WC, cm), triceps & subscapular skinfolds (mm), high-density lipoprotein (HDL, mg/dl), total cholesterol (TC, mg/dl), systolic & diastolic blood pressure (SBP & DBP, mm/hg), triglycerides (mg/dl), glycohemoglobin (%), insulin (μU/ml), & C-reactive protein (CRP, mg/dl). Each biomarker was regressed on each MVPA measure by sex. Covariates were age, race/ethnicity, SES, physical limitations, & asthma.

Results Girls recorded less time in MVPA [accelerometer: 18.2(0.9) vs. 33.6(1.3) min/day; self-report: 160.0(16.1) vs. 214.4(12.2) min/week, p<0.006. SRMVPA was significantly correlated with AMVPA (boys: r=0.16; girls: r=0.095; p<0.002). In boys, AMVPA was inversely associated with BMI, BMI percentile, height, WC, & triceps skinfold; & positively associated with HDL, & glycohemoglobin (p<0.05 for all). In boys, SRMVPA was inversely associated with DBP (p=0.001). In girls, AMVPA was inversely associated with SBP (p=0.046); & SRMVPA was not associated with biomarker.

Conclusions AMVPA showed stronger associations with biomarker than SRMVPA. SRMVPA may not relate to the biological aspects of MVPA as well as accelerometers. The associations between biomarker & both measures were stronger in boys. The lack of association in girls could reflect their low levels of MVPA.