Association of Obesity with Quantitative Chest CT Measured Airway Wall Thickness in WTC Workers with Lower Airway Disease

Impact of obesity on airway remodeling in asthma: pathophysiological insights and clinical implications

The prevalence of obesity among asthma patients has surged in recent years, posing a significant risk factor for uncontrolled asthma. Beyond its impact on asthma severity and patients' quality of life, obesity is associated with reduced lung function, increased asthma exacerbations, hospitalizations, heightened airway hyperresponsiveness, and elevated asthma-related mortality. Obesity may lead to metabolic dysfunction and immune dysregulation, fostering chronic inflammation characterized by increased pro-inflammatory mediators and adipocytokines, elevated reactive oxygen species, and reduced antioxidant activity. This chronic inflammation holds the potential to induce airway remodeling in individuals with asthma and obesity. Airway remodeling encompasses structural and pathological changes, involving alterations in the airway's epithelial and subepithelial layers, hyperplasia and hypertrophy of airway smooth muscle, and changes in airway vascularity. In individuals with asthma and obesity, airway remodeling may underlie heightened airway hyperresponsiveness and increased asthma severity, ultimately contributing to the development of persistent airflow limitation, declining lung function, and a potential increase in asthma-related mortality. Despite efforts to address the impact of obesity on asthma outcomes, the intricate mechanisms linking obesity to asthma pathophysiology, particularly concerning airway remodeling, remain incompletely understood. This comprehensive review discusses current research investigating the influence of obesity on airway remodeling, to enhance our understanding of obesity's role in the context of asthma airway remodeling.

Cluster Analysis of World Trade Center Related Lower Airway Diseases

ABSTRACT

Introduction: Cluster analysis can classify without a priori assumptions the heterogeneous chronic lower airway diseases found in former workers at the World Trade Center (WTC) disaster site. Methods: We selected the first available chest computed tomography scan with quantitative computed tomography measurements on 311 former WTC workers with complete clinical, and spirometric data from their closest surveillance visit. We performed a nonhierarchical iterative algorithm K-prototype cluster analysis, using gap measure. Results: A five-cluster solution was most satisfactory. Cluster 5 had the healthiest individuals. In cluster 4, smoking was most prevalent and intense but there was scant evidence of respiratory disease. Cluster 3 had symptomatic subjects with reduced forced vital capacity impairment (low FVC). Clusters 1 and 2 had less dyspneic subjects, but more functional and quantitative computed tomography evidence of chronic obstructive pulmonary disease (COPD) in cluster 1, or low FVC in cluster 2. Clusters 1 and 4 had the highest proportion of rapid first-second forced expiratory volume decliners. Conclusions: Cluster analysis confirms low FVC and COPD/pre-COPD as distinctive chronic lower airway disease phenotypes on long-term surveillance of the WTC workers.

Asthma-COPD overlap in World Trade Center Health Registry enrollees, 2015-2016

INTRODUCTION

Asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) is a newly redefined form of chronic airway disease and has not been well studied among 9/11-exposed populations with increased prevalence of asthma. We assessed the prevalence and risk factors associated with ACO in an exposure cohort of World Trade Center Health Registry (WTCHR) enrollees.

METHODS

This is a longitudinal study, including enrollees with complete data on 9/11/01 exposure at enrollment (2003-2004, Wave 1), asthma and COPD diagnoses and at least 25 years of age at the time of the 2015-2016 (Wave 4) WTCHR survey. Probable ACO was defined as self-reported post-9/11 physician-diagnosed asthma and either emphysema, chronic bronchitis, or COPD. We evaluated whether probable ACO was associated with World Trade Center (WTC)-related exposures, using multivariable logistic regression.

RESULTS

Of 36,864 Wave 4 participants, 29,911 were eligible for this analysis, and 1,495 (5.0%) had self-reported post-9/11 probable ACO. After adjusting for demographics and smoking status, we found 38% increased odds of having ACO in enrollees with exposure to the dust cloud, and up to 3.39 times the odds in those with ≥3 injuries sustained on 9/11. Among rescue/recovery workers, ever working on the pile, on the pile on 9/11 or 9/12/01, or working on the WTC site for >7 days showed increased odds ratios of having ACO.

CONCLUSION

Probable ACO is associated with WTC exposures. Further study of ACO is needed to understand the development of this and other environmentally or occupationally-related airway diseases, and how to prevent these in disasters like 9/11.

Quantitative CT Evidence of Airway Inflammation in WTC Workers and Volunteers with Low FVC Spirometric Pattern

BACKGROUND

The most common abnormal spirometric pattern reported in WTC worker and volunteer cohorts has consistently been that of a nonobstructive reduced forced vital capacity (low FVC). Low FVC is associated with obesity, which is highly prevalent in these cohorts. We used quantitative CT (QCT) to investigate proximal and distal airway inflammation and emphysema in participants with stable low FVC pattern.

METHODS

We selected study participants with at least two available longitudinal surveillance spirometries, and a chest CT with QCT measurements of proximal airway inflammation (wall area percent, WAP), end-expiratory air trapping, suggestive of distal airway obstruction (expiratory to inspiratory mean lung attenuation ratio, MLA_EI), and emphysema (percentage of lung volume with attenuation below - 950 HU, LAV%). The comparison groups in multinomial logistic regression models were participants with consistently normal spirometries, and participants with stable fixed obstruction (COPD).

RESULTS

Compared to normal spirometry participants, and after adjusting for age, sex, race/ethnicity, BMI, smoking, and early arrival at the WTC disaster site, low FVC participants had higher WAP (OR_adj 1.24, 95% CI 1.06, 1.45, per 5% unit), suggestive of proximal airway inflammation, but did not differ in MLA_EI, or LAV%. COPD participants did not differ in WAP with the low FVC ones and were more likely to have higher MLA_EI or LAV% than the other two subgroups.

DISCUSSION

WTC workers with spirometric low FVC have higher QCT-measured WAP compared to those with normal spirometries, but did not differ in distal airway and emphysema measurements, independently of obesity, smoking, and other covariates.