The Effects of Asthma on the Association Between Pulmonary Function and Obesity: A 16-Year Longitudinal Study

Background: Asthma and obesity are important public health issues around the world. Obesity is considered a risk factor associated with the severity and incidence of asthma. We investigated the relationships between poor pulmonary function (defined by forced vital capacity (FVC) and percentage of predicted FVC (FVC%)) and obesity. Methods: This is a retrospective longitudinal study using the MJ health examination database in Taiwan from 2000 to 2015. There were 160,609 participants aged >= 20 years with complete obesity indicators and lung function data, and having at least two visits. A generalized estimation equation (GEE) model was applied to estimate the association between lung function and obesity. Results: BMI was the best indicator to predict poor pulmonary function for our participants. Results of BMI are presented as an example: Obesity (body mass index (BMI) >= 27.0 kg/m(2)) is significantly associated with lower FVC [adjusted coefficients (beta) for asthmatics: -0.11 L (95% CI: -0.14, -0.08); adjusted beta for non-asthmatics: -0.08 L (-0.09, -0.08)] and FVC% [adjusted beta for asthmatics: -1.91% (95% CI: -2.64, -1.19); adjusted beta for non-asthmatics: 1.48% (-1.63, -1.33)]. Annual change of BMI (Delta BMI/year) is an independent risk factor for decreased FVC [adjusted beta for asthmatics: -0.030 L (-0.048, -0.013); adjusted beta for non-asthmatics: -0.019 L (-0.022, 0.016)] and FVC% [adjusted beta for non-asthmatics: -0.603% (-1.063, -0.142); adjusted beta for nonasthmatics: -0.304% (-0.393, -0.214)], and is significantly associated with accelerated FVC decline [adjusted beta of Delta FVC/year and Delta FVC %/year for asthmatics: -0.038 L (-0.054, -0.022) and -0.873% (-1.312, -0.435); adjusted beta of Delta FVC/year and Delta FVC %/year for non-asthmatics: 0.033 L (-0.042, -0.024) and -0.889% (-1.326, -0.452)]. Conclusion: Obesity is significantly associated with decreased lung function, and asthmatics had a higher risk than non-asthmatics.

Automated summary

The study revealed a significant association between obesity and decreased lung function, with BMI being the best indicator to predict poor pulmonary function. Annual change in BMI was found to be an independent risk factor for decreased FVC and FVC%, as well as for accelerated decline in lung function. Asthmatics were at a higher risk compared to non-asthmatics.