Tobacco Use and the Risk of COVID-19

March 5, 2024 updated by: Maria Rosaria Galanti, Karolinska Institutet

Smoking, Snus Use and the Risk of COVID-19 in a Cohort of Adult Client of Public Dentistry Clinics: is There a Causal Association?

Contrasting hypotheses, including that of a protective role of nicotine, have been generated concerning the association between smoking and the occurrence of COVID-19 infection. The question has attracted a lively scientific and public debate. However, the studies conducted so far are based on clinical samples, with a majority of hospital case series, thus most likely suffering from bias due to selection.

The investigators propose to conduct an analysis of the potential causal association between smoking or the use of the Swedish smokeless tobacco snus and the occurrence of COVID-19 using data from a newly identified retrospective cohort in Sweden. Information on tobacco use will be extracted by public dental clinic records in Stockholm Region between October 2015 and January 2020. Information on diagnoses of COVID-19 will be obtained through record linkage with health care registers of inpatient and outpatient care during the period February 2020-August 2021. Socio-demographic information will be accrued from the register of the total population in Stockholm Region (Statistics Sweden). The risk of COVID-19 for tobacco users compared to non-tobacco users will be calculated as a measure of association adjusting for potential confounders.

Study Overview

Status

Completed

Conditions

Intervention / Treatment

Detailed Description

Background The role of tobacco use in the incidence and in the prognosis of the Severe acute respiratory syndrome-Cov2 disease (COVID-19 pandemic) has raised much international interest, due to contrasting findings reported so far in the scientific literature. On one side smoking may increase the risk of adverse outcomes in clinically overt COVID-19 requiring hospital admission. Several cross-sectional studies (case series) indicated a higher risk of negative disease progression among smokers compared to non-smokers in cases hospitalized with severe symptoms of the disease. On the other side, studies also suggest also that smoking is associated with a decreased risk of hospital admission with a diagnosis of COVID-19, or a decreased risk of occurrence of the disease in the community. These studies have noted 4 to 5 times lower proportions of smokers among patients hospitalized for COVID-19 compared with the underlying source population. A metanalysis of hospital case series confirmed this gap.

Given the public health importance of tobacco use as a risk factor for morbidity and mortality, it is urgent to provide both the scientific and the broad lay community with sound information from large population studies, something that the World Health Organization has also recommended.

Aim The present study aims to elucidate the potential causal association between tobacco use (smoking and snus) and COVID-19 using a population-based cohort study.

Methods In Sweden, the public dental clinics collect information at each visit on lifestyle and co-morbidities with relevance for oral health (health declaration), with a uniform instrument in use from October 2015. Smoking and snus use are ascertained as past use, current use and categories of intensity of current use. During February 2020 the usual routine activity of the clinics was disrupted by the pandemic, and the so-called oral health check-up was discontinued. About 450 000 adult clients of the public dentistry in Stockholm Region were identified in the period October 2015 to January 2020. Among these about 120000 were assessed within 7 months from the onset of the pandemic, therefore represent recent experiences. The investigators expect about 9% to be smokers and about 11% to be snus users. With the help of the national personal numbers assigned to every resident in Sweden at birth or at immigration, the investigators will link the reports of smoking among these clients with diagnoses of COVID-19 and other comorbidities registered in the regional database of inpatient and outpatient health care. The information in the dental clinic registers will be linked to the total population of the region of Stockholm, in order to extract socio-demographic information.

Statistical analysis plan The investigators will examine the role of tobacco use on the risk of the following events: any diagnosis of COVID-19, hospitalization, receiving intensive care, and death because of COVID-19 using generalized linear models, with and without possible confounders (age, gender, country of birth, type of employment, education and cohabitation), and within subgroups to identify potential effect modification (age group, gender [in analyses of snus use], assumed infection risk associated to occupation, pandemic period, and strategies of virologic testing, very restricted in the first 3 months, available on individual request thereafter).

Study Type

Observational

Enrollment (Actual)

450000

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

23 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Sampling Method

Non-Probability Sample

Study Population

Adult clients of the public dental clinics in Stockholm Region (Sweden) in the period between October 2015 and January 2020.

Description

Inclusion Criteria:

  • Being a client of the public dental clinics in the region of Stockholm (Sweden) between October 2015 and January 2020
  • Being age 23 years or older
  • Having tobacco use habits recorded in at least one visit

Exclusion Criteria:

  • Not having a Swedish personal identity number
  • Resident in assisted elderly dwelling

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Observational Models: Cohort
  • Time Perspectives: Retrospective

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Cohort of adult client of public dental clinics in Region Stockholm
Tobacco use (cigarette smoking and/or snus use) will be considered as exposure. Information on tobacco use will be extracted by public dental clinic records in Stockholm Region (October 2015-January 2020). Any diagnosis of COVID-19, hospitalization, receiving intensive care, and death because of COVID-19 will be examined as outcomes. Diagnoses of COVID-19 will be obtained through record linkage with health care registers of inpatient and outpatient care (February 2020-August 2021).
Behavioral: Tobacco use

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Diagnosis of COVID-19
Time Frame: 18 months from the index case of the pandemic in Sweden
Incident diagnoses of COVID-19, whether symptomatic or not, corresponding to a positive virologic test (PCR)
18 months from the index case of the pandemic in Sweden
Hospital admission for COVID-19
Time Frame: 18 months from the index case of the pandemic in Sweden
Rates of hospital admission due to COVID-19 reported in the hospital register
18 months from the index case of the pandemic in Sweden
Intensive unit care because of a diagnosis of COVID-19
Time Frame: 18 months from the index case of the pandemic in Sweden
Rates of admission to Intensive care units (IU) with a diagnosis of COVID-19 reported in the hospital register
18 months from the index case of the pandemic in Sweden
Death for COVID-19
Time Frame: 18 months from the index case of the pandemic in Sweden
COVID-19 death rates where COVID-19 is mentioned as cause of death reported in the death register
18 months from the index case of the pandemic in Sweden

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Karolinska Institutet

Collaborators

Norwegian Institute of Public Health
Finnish Institute for Health and Welfare
Stockholm Region
Norforsk

Investigators

  • Principal Investigator: Maria Rosaria Galanti, PhD, Karolinska Institutet

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

October 1, 2015

Primary Completion (Actual)

December 31, 2023

Study Completion (Actual)

December 31, 2023

Study Registration Dates

First Submitted

May 20, 2021

First Submitted That Met QC Criteria

May 20, 2021

First Posted (Actual)

May 21, 2021

Study Record Updates

Last Update Posted (Actual)

March 6, 2024

Last Update Submitted That Met QC Criteria

March 5, 2024

Last Verified

March 1, 2024

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 4-1457/2021

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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