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Chronic obstructive pulmonary disease
Higher BMI is associated with higher expiratory airflow normalised for lung volume (FEF25–75/FVC) in COPD
  1. Eric Abston1,
  2. Alejandro Comellas1,2,
  3. Robert Michael Reed3,
  4. Victor Kim4,
  5. Robert A Wise5,
  6. Roy Brower5,
  7. Spyridon Fortis1,2,
  8. Reinhard Beichel1,6,7,
  9. Surya Bhatt8,
  10. Joseph Zabner1,2,
  11. John Newell7,9,
  12. Eric A Hoffman1,6,7,9 and
  13. Michael Eberlein1,2
  1. 1 Department of Medicine, University of Iowa, Iowa City, Iowa, USA
  2. 2 Division of Pulmonary, Critical Care and Occupational Medicine, University of Iowa, Iowa City, Iowa, USA
  3. 3 Division of Pulmonary and Critical Care Medicine, University of Maryland School of Medicine, Baltimore, Maryland, USA
  4. 4 Division of Pulmonary and Critical Care Medicine, Temple University, School of Medicine, Philadelphia, Pennsylvania, USA
  5. 5 Division of Pulmonary and Critical Care Medicine, Johns Hopkins University, Baltimore, Maryland, USA
  6. 6 Department of Electrical and Computer Engineering, University of Iowa, Iowa City, Iowa, USA
  7. 7 The Iowa Institute for Biomedical Imaging, University of Iowa, University of Iowa, Iowa City, Iowa, USA
  8. 8 Division of Pulmonary, Allergy and Critical Care Medicine, University of Alabama, Birmingham, Alabama, USA
  9. 9 Department of Radiology, University of Iowa, Iowa, USA
  1. Correspondence to Dr Michael Eberlein; michael-eberlein{at}uiowa.edu

Abstract

Introduction The obesity paradox in chronic obstructive pulmonary disease (COPD), whereby patients with higher body mass index (BMI) fare better, is poorly understood. Higher BMIs are associated with lower lung volumes and greater lung elastic recoil, a key determinant of expiratory airflow. The forced expiratory flow (25–75) (FEF25–75)/forced vital capacity (FVC) ratio reflects effort-independent expiratory airflow in the context of lung volume and could be modulated by BMI.

Methods We analysed data from the COPDGene study, an observational study of 10 192 subjects, with at least a 10 pack-year smoking history. Data were limited to subjects with BMI 20–40 kg/m2 (n=9222). Subjects were stratified according to forced expiratory volume in 1 s (FEV1) (%predicted)-quintiles. In regression analyses and Cox proportional hazard models, we analysed the association between BMI, the FEF25–75/FVC ratio, the imaging phenotype, COPD exacerbations, hospitalisations and death.

Results There was no correlation between BMI and FEV1(%predicted). However, a higher BMI is correlated with a higher FEF25–75/FVC ratio. In CT scans, a higher BMI was associated with less emphysema and less air trapping. In risk-adjusted models, the quintile with the highest FEF25–75/FVC ratio was associated with a 46% lower risk of COPD exacerbations (OR 0.54, p<0.001) and a 40% lower risk of death (HR 0.60, p=0.02), compared with the lowest quintile. BMI was not independently associated with these outcomes.

Conclusions A higher BMI is associated with lower lung volumes and higher expiratory airflows when normalised for lung volume, as quantified by the FEF25–75/FVC ratio. A higher FEF25–75/FVC ratio is associated with a lower risk of COPD exacerbations and death and might quantify functional aspects of the paradoxical effect of higher BMIs on COPD.

  • copd epidemiology
  • lung physiology

This is an Open Access article distributed in accordance with the terms of the Creative Commons Attribution (CC BY 4.0) license, which permits others to distribute, remix, adapt and build upon this work, for commercial use, provided the original work is properly cited. See: http://creativecommons.org/licenses/by/4.0/

https://doi.org/10.1136/bmjresp-2017-000231

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    Footnotes

    • Handling editor Matt P Wise

    • Contributors Conception and design: EA, APC, ME. Analysis and interpretation: EA, APC, RMR, VK, RGB, SF, SPB, RRB, JDN, EAH and ME. Drafting the manuscript: EA and ME. Review of the manuscript for important intellectual content: EA, APC, RMR, VK, RAW, RGB, SF, SPB, RRB, JZ, JDN, EAH and ME.

    • Funding The project described was supported by award number R01HL089897 and award number R01HL089856 from the National Heart, Lung and Blood Institute.

    • Competing interests None declared.

    • Ethics approval Each study site received Institutional Review Board approval to participate in the study.

    • Provenance and peer review Not commissioned; externally peer reviewed.

    • Collaborators Administrative Centre: James D Crapo, MD (PI); Edwin K Silverman, MD, PhD (PI); Barry J Make, MD; Elizabeth A Regan, MD, PhD. Genetic Analysis Centre: Terri Beaty, PhD; Ferdouse Begum, PhD; Robert Busch, MD; Peter J Castaldi, MD, MSc; Michael Cho, MD; Dawn L DeMeo, MD, MPH; Adel R Boueiz, MD; Marilyn G Foreman, MD, MS; Eitan Halper-Stromberg; Nadia N Hansel, MD, MPH; Megan E Hardin, MD; Lystra P Hayden, MD, MMSc; Craig P Hersh, MD, MPH; Jacqueline Hetmanski, MS, MPH; Brian D Hobbs, MD; John E Hokanson, MPH, PhD; Nan Laird, PhD; Christoph Lange, PhD; Sharon M Lutz, PhD; Merry-Lynn McDonald, PhD; Margaret M Parker, PhD; Dandi Qiao, PhD; Elizabeth A Regan, MD, PhD; Stephanie Santorico, PhD; Edwin K Silverman, MD, PhD; Emily S Wan, MD; Sungho Won. Imaging Centre: Mustafa Al Qaisi, MD; Harvey O Coxson, PhD; Teresa Gray; MeiLan K Han, MD, MS; Eric A Hoffman, PhD; Stephen Humphries, PhD; Francine L Jacobson, MD, MPH; Philip F Judy, PhD; Ella A Kazerooni, MD; Alex Kluiber; David A Lynch, MB; John D Newell, Jr, MD; Elizabeth A Regan, MD, PhD; James C Ross, PhD; Raul San Jose Estepar, PhD; Joyce Schroeder, MD; Jered Sieren; Douglas Stinson; Berend C Stoel, PhD; Juerg Tschirren, PhD; Edwin Van Beek, MD, PhD; Bram van Ginneken, PhD; Eva van Rikxoort, PhD; George Washko, MD; Carla G Wilson, MS. PFTQA Center, Salt Lake City, UT: Robert Jensen, PhD. Data Coordinating Center and Biostatistics, National Jewish Health, Denver, CO: Douglas Everett, PhD; Jim Crooks, PhD; Camille Moore, PhD; Matt Strand, PhD; Carla G Wilson, MS. Epidemiology Core, University of Colorado Anschutz Medical Campus, Aurora, CO: John E Hokanson, MPH, PhD; John Hughes, PhD; Gregory Kinney, MPH, PhD; Sharon M Lutz, PhD; Katherine Pratte, MSPH; Kendra A Young, PhD. Ann Arbor VA: Jeffrey L Curtis, MD; Carlos H Martinez, MD, MPH; Perry G Pernicano, MD. Baylor College of Medicine, Houston, TX: Nicola Hanania, MD, MS; Philip Alapat, MD; Mustafa Atik, MD; Venkata Bandi, MD; Aladin Boriek, PhD; Kalpatha Guntupalli, MD; Elizabeth Guy, MD; Arun Nachiappan, MD; Amit Parulekar, MD. Brighamand Women’s Hospital, Boston, MA: Dawn L. DeMeo, MD, MPH; Craig Hersh, MD, MPH; Francine L Jacobson,MD, MPH; George Washko, MD. Columbia University, New York, NY: R Graham Barr, MD, DrPH; John Austin, MD; Belinda D’Souza, MD; Gregory D N Pearson, MD; Anna Rozenshtein, MD, MPH, FACR; Byron Thomashow, MD Duke University Medical Center, Durham, NC: Neil MacIntyre, Jr, MD; H Page McAdams, MD; Lacey Washington, MD. Health Partners Research Institute, Minneapolis, MN: Charlene McEvoy, MD, MPH; Joseph Tashjian, MD. Johns Hopkins University, Baltimore, MD: Robert Wise, MD; Robert Brown, MD; Nadia N Hansel, MD, MPH; Karen Horton, MD; Allison Lambert, MD, MHS; Nirupama Putcha, MD, MHS. Los Angeles Biomedical Research Institute at Harbor UCLA Medical Center, Torrance, CA: Michael E DeBakey VAMC. Houston: Richard Casaburi, PhD, MD; Alessandra Adami, PhD; Matthew Budoff, MD; Hans Fischer, MD; Janos Porszasz, MD, PhD; Harry Rossiter, PhD; William Stringer, MD. TX: Amir Sharafkhaneh, MD, PhD; Charlie Lan, DO. Minneapolis VA: More house School of Medicine, Atlanta, GA: Marilyn G Foreman, MD, MS; Eugene Berkowitz, MD, PhD; Gloria Westney, MD, MS. National Jewish Health, Denver, CO: Russell Bowler, MD, PhD; David A Lynch, MB. Reliant Medical Group, Worcester, MA: Richard Rosiello, MD; David Pace, MD. Temple University, Philadelphia, PA: Gerard Criner, MD; David Ciccolella, MD; Francis Cordova, MD; Chandra Dass, MD; Gilbert D’Alonzo, DO; Parag Desai, MD; Michael Jacobs, PharmD; Steven Kelsen, MD, PhD; Victor Kim, MD; A James Mamary, MD; Nathaniel Marchetti, DO; Aditi Satti, MD; Kartik Shenoy, MD; RobertM Steiner, MD; Alex Swift, MD; Irene Swift, MD; Maria ElenaVega-Sanchez, MD. Universityof Alabama, Birmingham, AL: Mark Dransfield, MD; William Bailey, MD; Surya Bhatt, MD; Anand Iyer, MD; Hrudaya Nath, MD; J Michael Wells, MD. University of California, San Diego, CA: Joe Ramsdell, MD; Paul Friedman, MD; Xavier Soler, MD, PhD; AndrewYen, MD. Universityof Iowa, Iowa City, IA: Alejandro P Comellas, MD; John Newell, Jr, MD; Brad Thompson, MD. University of Michigan, Ann Arbor, MI: MeiLan K Han, MD, MS; Ella Kazerooni, MD; Carlos H. Martinez, MD, MPH. University of Minnesota, Minneapolis, MN: Joanne Billings, MD; Abbie Begnaud, MD; Tadashi Allen, MD. University of Pittsburgh, Pittsburgh, PA: Frank Sciurba, MD; Jessica Bon, MD; Divay Chandra, MD, MSc; CarlFuhrman, MD; Joel Weissfeld, MD, MPH. University of Texas Health Science Center at San Antonio, San Antonio, TX: Antonio Anzueto, MD; Sandra Adams, MD; Diego Maselli-Caceres, MD; Mario E Ruiz, MD.