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Original research
Physical activity paradox: could inflammation be a key factor?
  1. Joshua Buron Feinberg1,2,
  2. Anne Møller3,
  3. Volkert Siersma3,
  4. Helle Bruunsgaard4,5,
  5. Ole Steen Mortensen1,6
  1. 1 Department of Occupational and Social Medicine, Holbaek Hospital, Holbaek, Denmark
  2. 2 Faculty of Health Sciences, Institute of Regional Health, University of Southern Denmark, Odense, Denmark
  3. 3 Department of Public Health, The Research Unit for General Practice and Section of General Practice, University of Copenhagen, Copenhagen, Denmark
  4. 4 Department of Clinical Immunology, Rigshospitalet, Copenhagen, Denmark
  5. 5 Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark
  6. 6 Section of Social Medicine, Department of Public Health, University of Copenhagen, Copenhagen, Denmark
  1. Correspondence to Dr Joshua Buron Feinberg, Department of Occupational and Social Medicine, Holbaek Hospital, Holbaek 4300, Denmark; wtv945{at}alumni.ku.dk

Abstract

Objective The aim of this study was to test the extent to which physical activity performed during work and leisure is associated with systemic inflammation.

Methods Data regarding job history and high-sensitivity C reactive protein (hs-CRP) levels, as well as potential confounders, came from the Copenhagen Aging and Midlife Biobank. The participants’ self-reported job history was combined with a job exposure matrix to give a more valid assessment of cumulated occupational physical activity compared with conventional self-reported activity. Occupational physical activity was measured as cumulative ton-years (lifting 1000 kg each day for a year). Current leisure time physical activity was self-reported into four different categories. We analysed the association between occupational physical activity, current leisure time physical activity and hs-CRP level in a multivariable linear regression model with adjustment for age, sex, smoking history, number of chronic diseases, body mass index and alcohol.

Results In unadjusted analysis, higher occupational physical activity was associated with increased hs-CRP levels, while higher leisure time physical activity was associated with lower hs-CRP levels. In adjusted analysis, lower leisure time physical activity resulted in 12% higher hs-CRP levels while higher occupational physical activities showed a 6% increase in hs-CRP. When we analysed occupational and leisure time physical activity as continuous variables, only leisure time physical activity affected hs-CRP.

Conclusion This study indicates that the relationship between physical activity and hs-CRP depends on the setting of physical activity, with lower hs-CRP related to leisure time physical activity and higher hs-CRP related to occupational physical activity. The results suggest that systemic inflammation may explain the physical activity paradox.

  • Physical activity

Data availability statement

Data are available upon reasonable request. Request are made to the PI of CAMB. More information is available from https://camb.ku.dk/.

https://doi.org/10.1136/bjsports-2022-105429

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    Data availability statement

    Data are available upon reasonable request. Request are made to the PI of CAMB. More information is available from https://camb.ku.dk/.

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    Footnotes

    • Contributors OSM and AM conceived the study. JBF wrote the initial draft. AM and JBF performed the analysis with assistance from VS. VS provided overall statistical advice. All authors revised the manuscript and approved the final version. JBF serves as the guarantor.

    • Funding Salary for first author Joshua Buron Feinberg paid by the Danish Heart Foundation (grant number 19-R134-A8959-22123) and the University of Southern Denmark.

    • Competing interests None declared.

    • Patient and public involvement Patients and/or the public were not involved in the design, or conduct, or reporting, or dissemination plans of this research.

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

    • Supplemental material This content has been supplied by the author(s). It has not been vetted by BMJ Publishing Group Limited (BMJ) and may not have been peer-reviewed. Any opinions or recommendations discussed are solely those of the author(s) and are not endorsed by BMJ. BMJ disclaims all liability and responsibility arising from any reliance placed on the content. Where the content includes any translated material, BMJ does not warrant the accuracy and reliability of the translations (including but not limited to local regulations, clinical guidelines, terminology, drug names and drug dosages), and is not responsible for any error and/or omissions arising from translation and adaptation or otherwise.