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Asthma
Smoking and lung function among adults with newly onset asthma
  1. Jouni J K Jaakkola1,2,
  2. Samu Hernberg1,2,
  3. Taina K Lajunen1,2,
  4. Penpatra Sripaijboonkij1,2,3,
  5. L Pekka Malmberg4 and
  6. Maritta S Jaakkola1,2
  1. 1 Center for Environmental and Respiratory Health Research, University of Oulu, Oulu, Finland
  2. 2 Medical Research Center Oulu, Oulu, Finland, Oulu University Hospital
  3. 3 Physiotherapy and Sports Science, University College Dublin, Dublin, Ireland
  4. 4 Skin and Allergy Hospital, Helsinki University Hospital and Helsinki University, Helsinki, Finland
  1. Correspondence to Dr Jouni J K Jaakkola; jouni.jaakkola{at}oulu.fi

Abstract

Introduction Smoking increases the risk of asthma and reduces lung function among subjects with and without asthma. We assessed the effects of smoking on lung function reflecting both central and small airways among adults with newly onset asthma.

Methods In a population-based study, 521 (response rate 86%) working-aged adults with clinically defined newly diagnosed asthma answered a questionnaire on personal smoking and other factors potentially influencing lung function, and performed spirometry. We applied multiple linear regression analysis to estimate the relations between smoking and lung function adjusting for confounding.

Results Among asthmatics, FEV1 level was reduced significantly, on average 208 mL, related to regular smoking (adjusted effect estimate −0.208, 95% CI −0.355 to −0.061) and 245 mL in relation to former smoking, that is, among those who quit less than a year ago (−0.245, 95% CI −0.485 to −0.004). In contrast, FEV1 was not significantly related to occasional smoking or former smoking among those who quit over a year ago. Forced expiratory flow (FEF) levels (L/s) were also significantly reduced among regular smokers (FEF25–75%: −0.372, 95% CI −0.607 to −0.137; FEF50%: −0.476, 95% CI −0.750 to −0.202). An exposure–response pattern related to both daily smoking rate and lifetime cumulative smoking was seen both among men and women.

Conclusions This study provides new evidence that among working-aged adults with new asthma, regular smoking and former smoking reduce lung function levels with a dose–response pattern. The lung function parameters applied as outcomes reflect both larger and smaller airways.

  • smoking
  • lung function
  • small airways
  • asthmatics
  • bronchodilation test

This is an open access article distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited, appropriate credit is given, any changes made indicated, and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/.

https://doi.org/10.1136/bmjresp-2018-000377

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    Footnotes

    • Contributors JJKJ participated in conception and design of the study, acquisition of data, planning analyses and data interpretation, and wrote the article and serves as the corresponding author and the guarantor of the paper, taking responsibility for the integrity of the work as a whole. PS participated in data analysis and data interpretation and drafted the article. TKL analysed the data and participated in data interpretation and critical revision of the article. SH participated in data analysis and interpretation of data and critical revision of the manuscript. LPM provided expertise in clinical respiratory physiology. MSJ participated as the PI of the project in conception and design of the study, acquisition of data, planning analyses and data interpretation, and critical revision of the manuscript. All authors approved the final version of the manuscript to be submitted.

    • Funding This study was funded by the Academy of Finland (grants no. 138691 and no. 266314, and grant no. 129419 of SALVE research programme), the Ministry of Social Affairs and Health of Finland (grant no. STM/1523/2012), the Finnish Anti-Tuberculosis Association, Väinö and Laina Kivi Foundation, and Oulu University Hospital Research Fund.

    • Disclaimer The sponsors had no influence on the analysis or reporting of the results.

    • Competing interests None declared.

    • Patient consent for publication Not required.

    • Ethics approval The ethics committees of the Finnish Institute of Occupational Health and the Tampere University Hospital approved the study.

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

    • Data sharing statement No additional data are available.