About the Authors

Kristel S. Knudsen

Roles Writing – original draft

kristelknudsen@hotmail.com

Affiliations Department of Clinical Science, University of Bergen, Bergen, Norway, Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway

Sverre Lehmann

Roles Supervision, Writing – review & editing

Affiliations Department of Clinical Science, University of Bergen, Bergen, Norway, Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway

Rune Nielsen

Roles Supervision, Writing – review & editing

Affiliations Department of Clinical Science, University of Bergen, Bergen, Norway, Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway

Solveig Tangedal

Roles Formal analysis, Writing – review & editing

Affiliation Department of Clinical Science, University of Bergen, Bergen, Norway

Ingvild Haaland

Roles Formal analysis, Writing – review & editing

Affiliation Department of Clinical Science, University of Bergen, Bergen, Norway

Pieter S. Hiemstra

Roles Formal analysis, Methodology, Writing – review & editing

Affiliation Department of Pulmonology, Leiden University Medical Center, Leiden, Netherlands

Tomas M. Eagan

Roles Conceptualization, Formal analysis, Methodology, Project administration, Supervision, Writing – review & editing

Affiliations Department of Clinical Science, University of Bergen, Bergen, Norway, Department of Thoracic Medicine, Haukeland University Hospital, Bergen, Norway

Competing Interests

Data collection in the study was partially funded by a grant from the regional health authorities ("Helse-Vest") in 2014, to the last author, Tomas Eagan. Helse-Vest do not use grant numbers for their annual grant distribution. The funder web site is: "https://helse-vest.no/en/research-and-co-operation". Dr. Knudsen received grants from the Norwegian Thoracic Society and Boehringer Ingelheim during the study. This does not alter our adherence to PLOS ONE policies on sharing data and materials. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.