key: cord-1035978-v63fhrxp
authors: Yue, Limin; Zhang, Rongguang; Duan, Guangcai
title: The relationship between smoking and COVID-19 progression
date: 2020-11-27
journal: Nicotine Tob Res
DOI: 10.1093/ntr/ntaa245
sha: 72096de8aa5640ccbb937a29bbf3e5f123bd22f3
doc_id: 1035978
cord_uid: v63fhrxp

nan

A c c e p t e d M a n u s c r i p t Dear editor, Recently, Patanavanich et al. 1 conducted a systematic review and meta-analysis to explore the association of smoking with coronavirus (COVID-19) progression, based on 18 retrospective studies and one case series report. They found that smoking was a risk factor for COVID-19 progression. After reading this article, we found three questions that should be considered.

First, one study by Kim et al. 2 included in the meta-analysis collected 28 hospitalized COVID-19 patients, of whom only 27 had a clear smoking status. In addition, it was unclear whether the patient whose smoking status was not stated had progressed to COVID-19 or not.

The authors classified this patient as non-smoker. We think this approach is inappropriate and this study by Kim et al. 2 should be excluded because it cannot calculate a valid odds ratio. 3 Second, this meta-analysis combined retrospective studies and a case series report, and there was moderate heterogeneity among the studies. Combining different research types can increase heterogeneity. 4 We believe the case report should be excluded and only the retrospective studies included in the meta-analysis. For example, Arrich et al. 5 categories. But we found that another two studies (references 9 and 16 in this meta-analysis) also reported current and former smokers. Therefore, not only the meta-analysis comparing COVID-19 progression among current and former smokers, but also a meta-analysis comparing former smokers and never smokers could be performed. Patanavanich et al. 1 A c c e p t e d M a n u s c r i p t combined seven studies (references 12, 14, 18, 20, 23, 25, and 26 in this meta-analysis) that only reported current smokers with the other studies. That is to say, the authors considered non-current smokers as never smokers. This is not appropriate for non-current smokers include both former smokers and never smokers. Although the lung function of smokers could recover after stopping smoking, they would only partially recover. 8, 9 We believe a better approach would be to combine the seven studies which reported current smokers only (references 12, 14, 18, 20, 23, 25, and 26 in this meta-analysis) in a meta-analysis comparing progress among current smokers and non-current smokers, and the rest studies should be included in a meta-analysis comparing COVID-19 progress among people with a history of smoking ever and never smokers.

Taken together, the results of the meta-analysis by Patanavanich et al. 1 should be interpreted with caution. We hope that this comment will contribute to explaining and confirming their findings more accurately.

Smoking Is Associated With COVID-19 Progression: A Meta-analysis

Clinical Course and Outcomes of Patients with Severe Acute Respiratory Syndrome Coronavirus 2 Infection: a Preliminary Report of the First 28 Patients from the Korean Cohort Study on COVID-19

Understanding relative risk, odds ratio, and related terms: as simple as it can get

Meta-analysis of observational studies in epidemiology: a proposal for reporting. Meta-analysis Of Observational Studies in Epidemiology (MOOSE) group

Hypothermia for neuroprotection in adults after cardiopulmonary resuscitation

New Approaches to Airway Management in Tracheal Resections-A Systematic Review and Meta-analysis

Meta-analysis of treatment outcomes of posterior circulation non-saccular aneurysms by flow diverters

Respiratory function tests. Differences between smokers and non-smokers. Effects of withdrawal

Effects of randomized assignment to a smoking cessation intervention and changes in smoking habits on respiratory symptoms in smokers with early chronic obstructive pulmonary disease: the Lung Health Study

The authors declared no conflict of interest.

This study was funded by National Major Science and Technology Projects of China (2018ZX10301407) and National Natural Science Foundation of China (81773495).

A c c e p t e d M a n u s c r i p t