Active Smokers Are at Higher Risk of COVID-19 Death: A Systematic Review and Meta-analysis

Abstract

Introduction Current evidence indicates that smoking worsens COVID-19 outcomes. However, when studies restricted their analyses to current smokers, the risks for COVID-19 severity and death are inconsistent. This meta-analysis explored the association between current smoking and the risk for mortality based on the studies that reported all three categories of smoking (current, former, and never smokers) to overcome the limitation of the previous meta-analyses which former smokers might have been classified as non-smokers. Methods We searched PubMed and Embase up to 1 January 2021. We included studies reporting all three categories of smoking behaviors of COVID-19 patients and mortality outcomes. A random-effects meta-analysis and meta-regression were used to examine relationships in the data. Results A total of 34 articles with 35,193 COVID-19 patients was included. The meta-analysis confirmed the association between current smoking (OR 1.26, 95% CI: 1.01-1.58) and former smoking (OR 1.76, 95% CI: 1.53-2.03) with COVID-19 mortality. We also found that the risk for COVID-19 death in current smokers does not vary by age, but significantly drops by age in former smokers. Moreover, current smokers in non-high-income countries have higher risks of COVID-19 death compared with high-income countries (OR 3.11, 95% CI: 2.04-4.72 vs. OR 1.14, 95% CI: 0.91-1.43; p=0.015). Conclusions Current and former smokers are at higher risk of dying from COVID-19. Tobacco control should be strengthened to encourage current smokers to quit and prevent the initiation of smoking. Public health professionals should take the COVID-19 pandemic as an opportunity to promote smoking prevention and cession. Implications This study makes an important contribution to the existing literature by distinguishing between current and former smoking and their separate effects on COVID-19 mortality. We also explore the effects by age of patients and country income level. Findings from this study provide empirical evidence against misinformation about the relationship between smoking and COVID-19 mortality.

A population-based cohort study of sex and risk of severe outcomes in covid-19

“…Emerging evidence seems to support an association between smoking and more severe COVID-19 outcomes. [55,56] However, more women than men smoke daily in Sweden, although the difference is marginal. [57] Therefore, it is not likely that smoking status is a major driver of the observed sex disparity.…”

Commentary: Smoking, nicotine and COVID-19 outcomes: unprecedented challenges to epidemiologists

“…Nevertheless, a recent meta-analysis of observational studies showed that current and former smokers had higher risk of COVID-19 death. 3 …”

“… 4 (not included by Simons et al . 3 ) combining observational analysis and Mendelian randomization using the UK Biobank cohort, which reported that current smoking was associated with elevated risk of severe COVID-19. Gao et al .…”

Potential Bias in Assessing the Tobacco/Nicotine—COVID-19 Association—How to Improve Our Level of Understanding

“…According to currently available data, the role of smoking, tobacco, or other nicotine inhalation delivery systems’ use in acquiring SARS-CoV-2 infections is not established. In contrast, the harmful effect of tobacco smoking on the severity and mortality of COVID-19 is well-established [ 5 , 12 , 15 , 16 , 17 , 18 , 19 ]. This means that current regulatory strategies [ 20 ] to fight the tobacco epidemic should not be changed.…”