Relationship between Obesity Indices and Pulmonary Function Parameters in Obese Thai Children and Adolescents

To determine the correlation between various obesity indices and pulmonary function parameters in obese Thai children and adolescents.

Obese children and adolescents aged from 8 to 18 y and diagnosed under the criteria of International Obesity Task Force (IOTF) were enrolled. Anthropometric and body composition measurements (bioelectrical impedance analysis) of all eligible participants were recorded. Pulmonary function studies (spirometry and body plethysmography) were also performed on the same day.

Forty-five children and adolescents [84 % boys; mean age 11.9 ± 2.4 y; mean BMI 31.8 ± 5.1 kg/m(2); and, mean body mass index (BMI) z-score 3.2 ± 0.5] were studied. Mean body fat percentage, mean fat mass index (FMI), mean fat free mass index, and mean truncal fat percentage were 47.4 ± 10.2 %, 15.2 ± 5.2 kg/m(2), 16.3 ± 3.1 kg/m(2), and 47.7 ± 11.5 %, respectively. Abnormal lung functions were found in 73.2 % of subjects; the most common was decreased functional residual capacity (FRC) (29 cases; 64.4 %). There was a negative correlation between FRC and BMI z-score (r = -0.32; p 0.03), waist-height ratio (r = -0.32; p 0.02), body fat percentage (r = -0.32; p 0.03), FMI (r = -0.36; p 0.02), and truncal fat percentage (r = -0.32; p 0.04). Obese individuals who had FMI > 17 kg/m(2) were 5.7 times more likely to have decreased FRC than those who had lower FMI (95 % CI 1.1-29.7; p 0.016).

Decreased FRC was the most common pulmonary function abnormality in obese children and adolescents. BMI z-score, waist-height ratio, body fat percentage, FMI, and truncal fat percentage were all negatively correlated with FRC. FMI had the highest negative correlation. Obese individuals with FMI > 17 kg/m(2) had a 5.7 times increased risk of low FRC. Appropriate planning for respiratory care and follow-up may be required in this population.