Risk factors for COVID-19: A test-negative case-control study

Abstract

Background: There are conflicting findings about the associations between smoking, obstructive lung disease and COVID-19. Objectives: To assess risk factors for COVID-19, by comparing PCR positive (PCR+) cases with PCR negative (PCR-) controls using a test-negative case-control study design, including population controls. Methods: This observational, multicenter test-negative case-control study included SARS-CoV-2 RT- PCR (Real-time –polymerase chain reaction) positive and negative participants from south-eastern Norway between February and December 2020. The study included the first and second pandemic waves in Norway, dominated by the alpha virus. A self-reported questionnaire about possible risk factors was completed by the participants 3-5 months after the first PCR test. We applied univariate and multiple regression analysis. Results: 400 PCR+ cases and 719 PCR- controls were included. The mean age of PCR+ cases and PCR- controls was 48±15 years and 47±14 years, respectively. Only six percent of participants were hospitalized. Male participants were represented in 49% of PCR+ and 34% of PCR- participants. Asthma was present in 64 (16%) of the PCR+ compared to 135 (19%) of the PCR- participants. Male gender was positively associated with risk for COVID-19 (OR 1.9, 95% CI; 1.4 to 2.6). For smoking the OR was 0.5, 95% CI 0.3 to 0.8. Non-statistically significant negative associations were observed between asthma and COVID-19 (OR 0.83, 95% CI; 0.6 to 1.2) and between COPD and COVID-19 (OR 0.41, 0.13 to 1.11). Conclusions: Male gender was positively associated with COVID-19 infection in this test-negative study. Smoking was negatively associated with COVID-19 and no association was detected between asthma or COPD and COVID-19.

Authors 14

1. Marjut Sarjomaa

   University of Oslo

   Affiliation as printed

   Telemark Hospital, University of Oslo, Skien, Norway

2. Randi Eikeland

   University of Agder · Sørlandet Hospital Arendal · Sørlandet Sykehus

   Affiliation as printed

   Sørlandet Hospital, University of Agder, Arendal, Norway

3. Chi Zhang

   Norwegian Institute of Public Health

   Affiliation as printed

   Norwegian Institute of public Health, Oslo, Norway

4. Yngvar Tveten

   Telemark Hospital

   Affiliation as printed

   Telemark Hospital, Skien, Norway

5. Harald Reiso

   Sørlandet Hospital Arendal

   Affiliation as printed

   Sørlandet Hospital, Arendal, Norway

6. Carina Thilesen

   Unilabs (Norway)

   Affiliation as printed

   Unilabs, Skien, Norway

7. Svein Arne Nordbø

   Norwegian University of Science and Technology · St Olav's University Hospital

   Affiliation as printed

   St Olavs Hospital, Norwegian University of science and technology, Trondheim, Norway

8. Kristine Karlsrud Berg

   Sørlandet Sykehus

   Affiliation as printed

   Sørlandet Hospital, Kristiansand, Norway

9. Ingeborg Aaberge

   Norwegian Institute of Public Health

   Affiliation as printed

   Norwegian Institute of public Health, Oslo, Norway

10. Johny Steinar Kongerud

    University of Oslo

    Affiliation as printed

    University of Oslo, Oslo, Norway

11. Neil Pearce

    London School of Hygiene & Tropical Medicine

    Affiliation as printed

    London School of Hygiene and tropical Medicine, London, United Kingdom

12. Hege Kersten

    University of Oslo

    Affiliation as printed

    Telemark Hospital, University of Oslo, Skien, Norway

13. Jan Paul Vandenbroucke Aachen London School of Hygiene and Tropical Medicine

    Leiden University · London School of Hygiene & Tropical Medicine

    Affiliation as printed

    London School of Hygiene and Tropical Medicine, University of Leiden, University of Aalborg, London, Leiden, Aalborg, Netherlands

14. Anne Kristin Møller Fell

    University of Oslo

    Affiliation as printed

    Telemark Hospital, University of Oslo, Skien, Norway