Variability of thinness and its relation to cardio-metabolic risk factors using four body mass index references in school-children from Delhi, India.

OBJECTIVES To compare: (i) prevalences of thinness in school-children by four body mass index references in common use viz., Centre for Disease Control (CDC); Cole; Indian Academy of Pediatrics (IAP); World Health Organization (WHO); and (ii) relationship of thinness with absence of cardio-metabolic risk factors in these BMI references. DESIGN Cross-sectional. SETTING Schools in Delhi. PARTICIPANTS Anthropometry and blood pressure were measured in 16,245 school children aged 5 to 18 years. Fasting lipids and blood sugar were estimated in 2796 subjects. OUTCOME MEASURES Age and sex-specific prevalences of thinness and predictive ability of reference cut-off for detecting any cardio-metabolic risk factor were compared. RESULTS Prevalence of thinness varied with the reference employed; more so for boys. Overall prevalence of thinness was least with IAP reference and highest with CDC cut-offs (6.6% to 16.9% in boys, 6.5% to 10.3% in girls). Children identified as thin by any reference had comparable, significantly lower risks (OR 0.59 to 0.73) of associated cardio-metabolic aberrations. In subjects with any cardio-metabolic or blood pressure aberration, the prevalence of thinness was highest with CDC and least with IAP definition. CONCLUSION Prevalence of thinness varies considerably with the reference employed. Thin children, identified by any reference, have a lower risk of associated cardio-metabolic aberrations; however, thinness is a poor diagnostic test for this purpose. In populations undergoing nutrition transition, there is a need to link cardio-metabolic risk factors with recommended anthropometric criteria to define undernutrition.