Rationale: Available prospective studies of obesity and asthma have used only body mass index (BMI) as an indicator for adiposity; studies using detailed obesity measures are lacking, and the role of physical fitness level and sedentary time remains unexplored in the link between obesity and asthma.
Objectives: To compare various anthropometric measures of obesity in relation to childhood asthma, and to further characterize the interrelations among central obesity, physical fitness level, sedentary time, and asthma.
Methods: The nationwide Taiwan Children Health Study followed 2,758 schoolchildren from fourth to sixth grade, annually collecting data regarding physical fitness, sedentary time, obesity measures (comprising body weight and height, abdominal and hip circumference, skin fold thickness, and body composition), asthma, and pulmonary function tests. The generalized estimating equation was used for 3 years of repeated measurements to analyze the interrelation among obesity, sedentary time, physical fitness level, and asthma; a structural equation model was used to explore the pathogenesis among these factors. Asthma incidence was analyzed during a 2-year follow-up among centrally obese and nonobese groups in baseline children without asthma.
Measurements and main results: Central obesity most accurately predicts asthma. Low physical fitness levels and high screen time increase the risk of central obesity, which leads to asthma development. Obesity-related reduction in pulmonary function is a possible mechanism in the pathway from central obesity to asthma.
Conclusions: Central obesity measures should be incorporated in childhood asthma risk predictions. Children are encouraged to increase their physical fitness levels and reduce their sedentary time to prevent central obesity-related asthma.