The effects of asthma on the association between pulmonary function and obesity: A 16-year longitudinal study

Abstract

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/m2) is significantly associated with lower FVC [adjusted coefficients (β) for asthmatics:-0.11 L (95% CI:-0.14,-0.08); adjusted β for non-asthmatics:-0.08 L (-0.09,-0.08)] and FVC% [adjusted β for asthmatics:-1.91% (95% CI:-2.64,-1.19); adjusted β for non-asthmatics: 1.48% (-1.63,-1.33)]. Annual change of BMI (ΔBMI/year) is an independent risk factor for decreased FVC [adjusted β for asthmatics:-0.030 L (-0.048,-0.013); adjusted β for non-asthmatics:-0.019 L (-0.022,-0.016)] and FVC% [adjusted β for non-asthmatics:-0.603% (-1.063,-0.142); adjusted β for non-asthmatics:-0.304% (-0.393,-0.214)], and is significantly associated with accelerated FVC decline [adjusted β of ΔFVC/year and ΔFVC %/year for asthmatics:-0.038 L (-0.054,-0.022) and-0.873% (-1.312,-0.435); adjusted β of ΔFVC/year and ΔFVC %/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.