Tobacco Use and COVID-19 Incidence in the Finnish General Population

Completed

• Conditions: SARS-CoV-2 Infection; Covid19
• Interventions: Other: Not applicable, this is an observational study

• Registration Number: NCT04915781
• Lead Sponsor: Finnish Institute for Health and Welfare

Brief Summary

This is an observational study of participants in three general population health surveys (FinSote 2018, 2019, 2020) who are followed up until the incidence of SARS-CoV-2 infection or end of follow-up. The primary objective is to examine the association between tobacco use and the risk of SARS-CoV-2 infection in a general population sample in Finland.

Detailed Description

Tobacco use, as a leading risk factor of death and disability due to respiratory diseases, was expected to increase the risk of SARS-CoV-2 infection and COVID-19 deaths. Earlier epidemiological studies, however, showed that smokers were underrepresented among patients hospitalized due to COVID-19. The most recent meta-analysis has confirmed these early findings, showing that current smokers had lower risk of SARS-CoV-2 infection than never smokers (Relative risk 0.71, 95% Credible interval 0.61; 0.82). A majority of these studies are based on samples of hospitalized patients, tested population or specific population groups, which might not represent the general population. In addition, data on tobacco use has been primarily collected from electronic health records or retrospectively and therefore prone to misclassification and information bias.

A message of a protective effect of tobacco use could undermine public health efforts to curb its use and reduce the perception of harm in the general population. Studies with general population samples and prospective data collection are thus urgently needed.

The aim of the study is to examine the association between tobacco use and the risk of SARS-CoV-2 infection. We will explore several forms of tobacco use (smoking, moist smokeless tobacco and e-cigarettes) and investigate whether introducing a potential collider bias by adjusting for mediating risk factors (alcohol use, physical activity and obesity) could have explained earlier results. We will use data from a prospective cohort study of nationally representative health surveys in Finland linked to SARS-CoV-2 incidence data, which is less subject to collider and recall bias than previous case-control studies.

Study Timeline

• Study Start: 2017-10-02
• Study First Submitted: 2021-06-03
• Study First Submitted QC: 2021-06-04
• Study First Posted: 2021-06-07
• Primary Completion: 2021-12-30
• Study Completion: 2021-12-30
• Status Verified: 2022-06
• Last Update Submitted: 2022-06-16
• Last Update Posted: 2022-06-22

Recruitment & Eligibility

• Status: COMPLETED
• Sex: All
• Target Recruitment: 60872

Inclusion Criteria

• Permanent residents of Finland
• Registered in the Population Register at the moment of sampling
• Aged 20 and over
• Participated in the FinSote surveys in 2018, 2019 or 2020

Exclusion Criteria

• Temporary residents in Finland or tourists
• Age less than 20 years old
• Did not participate in FinSote surveys in 2018, 2019 and 2020

Study & Design

• Study Type: OBSERVATIONAL
• Study Design: Not specified

Arm && Interventions

Group	Intervention	Description
Tobacco users	Not applicable, this is an observational study	Never smokers (reference group) will be compared with former smokers, occasional smokers and daily smokers. For FinSote 2018 and 2020, we will also compare never users of (1) smokeless tobacco (snus), (2) electronic cigarettes with and without nicotine or (3) nicotine replacement therapy products with respective former, occasional and daily users.

Primary Outcome Measures

Name	Time	Method
Incidence of SARS-CoV-2 infection	Baseline until SARS-CoV-2 infection or April 30, 2021	Incidence is the detection of a new SARS-CoV-2 infection with RT-PCR or a COVID-19 syndrome diagnosed by a physician from baseline to April 30, 2021

Trial Locations

Locations (1)

Finland; 🇫🇮 Helsinki, Finland