Effect of Body Mass Index on Lung Function in Chinese Patients with Chronic Obstructive Pulmonary Disease: A Multicenter Cross-Sectional Study

Associations between different body mass index and lung function impairment in Chinese people aged over 40 years: a multicenter cross-sectional study

OBJECTIVE

The aim of this study was to explore the associations between different body mass index (BMI) levels and different lung function impairment (LFI) in Chinese people aged over 40 years.

METHODS

We used a multi-stage stratified cluster random sampling method to investigate 3000 residents aged over 40 years from 5 areas in Hubei province of China in 2019-20. The data on questionnaire, physical measurements, and spirometry of the participants were collected. The associations of different BMI levels with different LFI were analyzed using multivariate logistic regressions after complex weighting. The spirometry data were analyzed using one-factor analysis of variance (ANOVA), and post-hoc was performed using the least significance difference (LSD)-t test.

RESULTS

A total of 2860 subjects were included. The prevalence (95%CI) of obstructive lung disease (OLD), restrictive lung disease (RLD), mixed lung disease (MLD), chronic obstructive pulmonary disease (COPD), COPD mild, and COPD moderate/severe/very severe were 24.1% (95% CI: 22.2-26.2), 11.6% (95% CI: 10.3-12.9), 4.0% (95% CI: 3.3-4.8), 12.6% (95% CI: 11.0-14.1), 7.2% (95% CI: 6.0-8.4), and 5.3% (95% CI: 4.3-6.4) respectively. After multivariate adjustment, the risk of OLD, COPD, and COPD mild decreased with the increment of BMI levels (both P for trend < 0.05). When compared to the normal weight group, the overweight group and obese group were at lower risk of experiencing OLD than normal group, the ORs were 0.77 (95% CI: 0.59-0.99) and 0.59 (95% CI: 0.40-0.86) respectively. The obese group was at lower risk for people with COPD mild (OR: 0.42, 95%CI: 0.21-0.85). Participants in underweight group were more likely to experience COPD and COPD moderate/severe/very severe, the ORs were 2.82 (95% CI: 1.07-7.39) and 3.89 (95% CI: 1.28-11.87) respectively.

CONCLUSION

Higher BMI levels were associated with an decreased risk of OLD and COPD. Obesity had a protective effect on lung function in OLD patients and COPD patients. However, there was no significant difference in RLD and MLD prevalence between different BMI groups.

Analysis of the correlation between BMI and respiratory tract microbiota in acute exacerbation of COPD

Objective

To investigate the distribution differences in the respiratory tract microbiota of AECOPD patients in different BMI groups and explore its guiding value for treatment.

Methods

Sputum samples of thirty-eight AECOPD patients were collected. The patients were divided into low, normal and high BMI group. The sputum microbiota was sequenced by 16S rRNA detection technology, and the distribution of sputum microbiota was compared. Rarefaction curve, α-diversity, principal coordinate analysis (PCoA) and measurement of sputum microbiota abundance in each group were performed and analyzed by bioinformatics methods.

Results

1. The rarefaction curve in each BMI group reached a plateau. No significant differences were observed in the OTU total number or α-diversity index of microbiota in each group. PCoA showed significant differences in the distance matrix of sputum microbiota between the three groups, which was calculated by the Binary Jaccard and the Bray Curtis algorithm. 2. At the phylum level, most of the microbiota were Proteobacteria, Bacteroidetes Firmicutes, Actinobacteria, and Fusobacteria. At the genus level, most were Streptococcus, Prevotella, Haemophilus, Neisseria and Bacteroides. 3. At the phylum level, the abundance of Proteobacteria in the low group was significantly higher than that in normal and high BMI groups, the abundances of Firmicutes in the low and normal groups were significantly lower than that in high BMI groups. At the genus level, the abundance of Haemophilus in the low group was significantly higher than that in high BMI group, and the abundances of Streptococcus in the low and normal BMI groups were significantly lower than that in the high BMI group.

Conclusions

1. The sputum microbiota of AECOPD patients in different BMI groups covered almost all microbiota, and BMI had no significant association with total number of respiratory tract microbiota or α-diversity in AECOPD patients. However, there was a significant difference in the PCoA between different BMI groups. 2. The microbiota structure of AECOPD patients differed in different BMI groups. Gram-negative bacteria (G-) in the respiratory tract of patients predominated in the low BMI group, while gram-positive bacteria (G+) predominated in the high BMI group.

The Relationship Between BMI and Lung Function in Populations with Different Characteristics: A Cross-Sectional Study Based on the Enjoying Breathing Program in China

Purpose

To analyze the relationship between body mass index (BMI) and lung function, which may help optimize the screening and management process for chronic obstructive pulmonary disease (COPD) in the early stages.

Patients and Methods

In this cross-sectional study using data from the Enjoying Breathing Program in China, participants were divided into two groups according to COPD Screening Questionnaire (COPD-SQ) scores (at risk and not at risk of COPD) and three groups based on lung function (normal lung function, preserved ratio impaired spirometry [PRISm], and obstructive lung function).

Results

A total of 32,033 subjects were enrolled in the current analysis. First, in people at risk of COPD, overweight and obese participants had better forced expiratory volume in one second (FEV1; overweight: 0.33 liters (l), 95% confidence interval [CI]: 0.27 to 0.38; obesity: 0.31 L, 95% CI: 0.22 to 0.39) values than the normal BMI group. Second, among people with PRISm, underweight participants had a lower FEV1 (−0.56 L, 95% CI: −0.86 to −0.26) and forced vital capacity (FVC; −0.33 L, 95% CI: −0.55 to −0.11) than participants with a normal weight, and obese participants had a higher FEV1 (0.22 L, 95% CI: 0.02 to 0.42) and FVC (0.16 L, 95% CI: 0.02 to 0.30) than participants with a normal weight. Taking normal BMI as the reference group, lower FEV1 (−0.80 L, 95% CI: −0.97 to −0.63) and FVC (−0.53 L, 95% CI: −0.64 to −0.42) were found in underweight participants with obstructive spirometry, and better FEV1 (obesity: 0.26 L, 95% CI: 0.12 to 0.40) was found in obese participants with obstructive spirometry.

Conclusion

Being underweight and severely obese are associated with reduced lung function. Slight obesity was shown to be a protective factor for lung function in people at risk of COPD and those with PRISm.

The associations between body composition and vital capacity index of medical students in Shenyang of China: a cross-sectional survey

Objectives

This study aimed to examine the associations between body composition and vital capacity index (VCI) among medical students of Shenyang, China.

Study design

The design of this study is a cross-sectional study.

Methods

Participants were 2063 individuals (17–25 years) from a medical college in Shenyang, who participated in this survey from April to May 2017. Height, weight, fat mass (FM), fat free mass (FFM), protein mass (PM), total body water (TBW), mineral mass (MM), vital capacity were measured, then BMI and VCI were calculated. Stepwise multiple linear regression analysis was used to evaluate the effect of body composition on VCI of participants in different genders. In addition, subgroup analysis was carried out according to BMI levels.

Results

Male students showed significantly higher height, weight, BMI, FFM, PM, TBW, MM, VC, and VCI, but lower FM in comparison with female students. Stepwise multiple linear regression analysis showed that in both sexes FM was negatively correlated with VCI which represents pulmonary function (r < 0; P < 0.001). After dividing the whole participants by BMI, further correlation analysis showed FM was positively correlated with VCI only for male subgroups with BMI < 18.5 (r > 0; P = 0.050).

Conclusion

Overall, FM is highly negatively correlated with the VCI of Chinese medical students of both genders. However, there was a positive correlation between FM and VCI among low-weight male students.