Interactive effects of adiposity and insulin resistance on the impaired lung function in asthmatic adults: cross-sectional analysis of NHANES data

Background: Obesity is considered a risk factor for both asthma and insulin resistance in adults. Insulin resistance (IR) also influences pulmonary function in the non-obese population.Aim: To investigate the modifying effect of insulin resistance on the predictive role of anthropometric measures in the estimation of impaired lung function among asthmatic adults.Subjects and methods: A cross-sectional study of 1276 adults extracted from the NHANES 2009–2012 database was performed. Adjusted multiple linear regression was conducted to analyse the contributory role of obesity and IR in predicting lung function among asthmatic adults.Results: BMI, waist circumference (WC) and waist-to-height ratio (WHtR) showed significantly negative correlations with FVC (r=–0.24, –0.18, –0.39, respectively; p < 0.001), FEV1(r=–0.24, –0.21, –0.40, respectively; p < 0.001) and FEF 25–75% (r=–0.15, –0.18, –0.27, respectively; p < 0.001). Even after adjustment for the covariates (age, gender, smoking history and standing height), BMI and HOMA-IR had significant relationships with FVC (β= −10.3; p < 0.01 and β= −16.0; p < 0.05) and FEV1 (β= −8.7; p < 0.01 and β= −11.7; p < 0.05). BMI could significantly predict the decreased FVC (β= −13.7; p < 0.01) and FEV1 (β= −10.7; p < 0.01) only in the insulin resistant asthmatics.Conclusion: WHtR and IR predict impaired lung function in overweight/obese asthmatic adults independently. IR also modifies the association between excessive adiposity and respiratory function in asthmatic adults.