Using physical examinations to estimate age in elementary school children: A Chinese population-based study

BACKGROUND: Designing a simple and accessible approach to age estimation in children and youth is a great challenge in the fields of sports and physical activity (PA). This study was designed to develop and validate a physical-examination-based method of estimating age in young children. METHODS: In a cross-sectional study conducted in 2014, we performed physical examinations and assessed PA among 14,970 elementary school children 7–12 years old in Shanghai, China. Additional biological information on the children's height and birth date was ascertained through their parents. Two indicators were applied to develop a gender-specific age estimation equation: The percentage of predicted mature height (PPMH) and the Tanner stage. The equation was validated through a k-fold cross-validation approach. To check for estimation accuracy, the association between the discrepancy of estimated age (EA) and chronological age and PA was examined. RESULTS: The gender-specific equations of EA were as follows: EA(boy) = –6.071 + 6.559 Tanner 2 + 13.315 Tanner 3 + 14.130 Tanner 4 + 0.190 PPMH – 0.071 Tanner 2 × PPMH – 0.146 Tanner 3 × PPMH – 0.155 Tanner 4 × PPMH; EA(girl) = –4.524 – 1.251 Tanner 2 + 2.504 Tanner 3 + 8.752 Tanner 4 + 11.893 Tanner 5 + 0.158 PPMH + 0.017 Tanner 2 × PPMH – 0.024 Tanner 3 × PPMH – 0.087 Tanner 4 × PPMH – 0.118 Tanner 5 × PPMH. The mean absolute error was 0.60 years for boys and 0.59 years for girls. The discrepancy score was negatively and weakly associated with self-reported moderate-to-vigorous PA in both genders (r(boy) = –0.09, p < 0.001; r(girl) = –0.12, p < 0.001). CONCLUSION: Findings suggest that physical examinations could provide a valid and reliable approach for estimating age in young Chinese children.