Elsevier

Respiratory Medicine

Volume 195, April–May 2022, 106792
Respiratory Medicine

Short communication
Association of BMI with pulmonary function, functional capacity, symptoms, and quality of life in ILD

https://doi.org/10.1016/j.rmed.2022.106792Get rights and content

Highlights

  • Increasing BMI is associated with worse pulmonary function, functional capacity, dyspnea, and quality of life in ILD.

  • Mass loading of the thorax in higher BMI categories could exacerbate the restrictive pulmonary defect characteristic of ILD.

  • Intentional weight-loss in overweight and obese patients may improve pulmonary function in addition to functional capacity.

Abstract

Obesity is a health epidemic associated with greater morbidity and mortality in the general population. Mass loading of the thorax from obesity leads to a restrictive pulmonary defect that reduces lung capacity in obese individuals without pulmonary disease, and may exacerbate the restrictive pulmonary physiology that is characteristic of interstitial lung disease (ILD). The purpose of this study was to test the association of body mass index (BMI) with pulmonary function, functional capacity, and patient-reported outcomes (dyspnea and quality of life) in patients with ILD. We analyzed 3169 patients with fibrotic ILD from the Canadian Registry for Pulmonary Fibrosis. Patients were subcategorized as underweight (BMI<18.5 kg/m2), normal weight (18.5≤BMI<25), overweight (25≤BMI<30), obese I (30≤BMI<35), obese II (35≤BMI<40), and obese III (BMI>40). Analysis was performed using a linear regression with adjustment for common prognostic variables. Overweight and obese BMI categories were associated with worse pulmonary function, functional capacity, dyspnea, and quality of life compared to normal weight. This is likely a result of mass loading on the thorax, and we speculate that intentional weight-loss may improve lung function and functional capacity in obese patients with fibrotic ILD. The underweight BMI category was also associated with worse functional capacity compared to normal weight, which may reflect greater disease severity or the presence of other comorbidities. Future work should explore the clinical utility of BMI to improve patient outcomes.

Introduction

Fibrotic interstitial lung diseases (ILDs) are associated with significant morbidity, most notably dyspnea, reduced exercise tolerance, and poor quality of life. Higher body mass index (BMI) is associated with increased mortality in the general population [1], but conversely associated with lower all-cause mortality in both chronic obstructive pulmonary disease (COPD) and fibrotic ILD [[2], [3], [4], [5]]; however, the impact of BMI on morbidity in ILD is unknown. In this study, we tested the association of baseline BMI with pulmonary function, functional capacity, and patient-reported outcomes (dyspnea and quality of life) in fibrotic ILD, hypothesizing that increasing BMI would be associated with greater morbidity.

Section snippets

Methods

This retrospective study included patients with fibrotic ILD from the Canadian Registry for Pulmonary Fibrosis who had at least one measurement of height and body mass [6]. Research ethics board approval was obtained at all participating sites (coordinating site: University of British Columbia H19-01989).

BMI was calculated based on the first available measurements of height and body mass from pulmonary function testing (i.e., baseline) and subcategorized as underweight (BMI<18.5 kg/m2), normal

Results

A total of 3169 patients (50% male) were included, with mean age 62 ± 13 years, BMI 28.8 ± 5.8 kg/m2 (1% underweight, 25% normal weight, 37% overweight, 23% obese I, 9% obese II, and 4% obese III), FVC 79 ± 20 %-predicted, and DLCO 62 ± 20 %-predicted.

The unadjusted association of BMI category with each outcome variable is shown in Fig. 1. The lowest and highest BMI groups had the lowest 6MWD and EQ5D VAS, while UCSD SOBQ scores were highest in the obese groups. Normal weight was typically

Discussion

Obesity is increasing in prevalence and considered a health epidemic in many countries [7]. Beyond the previously demonstrated association of BMI with mortality in patients with fibrotic ILD [5], we show that: 1) overweight and particularly obese BMI categories are associated with lower pulmonary function, lower functional capacity, worse dyspnea, and poorer quality of life compared to normal weight; and 2) the underweight BMI category is also associated with worse functional capacity compared

Funding

The CAnadian REgistry for Pulmonary Fibrosis (CARE-PF) is funded by Boehringer Ingelheim (Grant #: 20R23666).

Role of the sponsors

The funders had no role in the study design, data collection and analysis, or preparation of the manuscript.

Other contributions

The authors thank the patients who agreed to participate in the CARE-PF registry.

Summary of conflicts of interest statements

None of the authors report competing interests.

Financial/non-financial disclosures

DA, NK, MK, HM, and CJR report grants from Boehringer Ingelheim. DA, JHF, KAJ, NK, MK, VM, and CJR report personal fees from Boehringer Ingelheim. DA, KAJ, MK, VM, and CJR report personal fees from Hoffman La Roche. JHF, KAJ, and CJR report personal fees from Astra Zeneca. MK, VM, and CJR report grants from Hoffman La Roche. MK and CJR report personal fees from Cipla Ltd. JHF also reports grants from the Canadian Pulmonary Fibrosis Foundation, where she served on the medical advisory board, and

CRediT authorship contribution statement

Michele R. Schaeffer: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Software, Visualization, Writing – original draft, Writing – review & editing. Divjot S. Kumar: Conceptualization, Data curation, Formal analysis, Investigation, Methodology, Writing – original draft, Writing – review & editing. Deborah Assayag: Investigation, Project administration, Writing – review & editing. Jolene H. Fisher: Investigation, Project administration, Writing – review & editing.

References (10)

There are more references available in the full text version of this article.
View full text