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. 2021 Jul 1;115(7):820-831.
doi: 10.1093/trstmh/traa172.

Tobacco, alcohol use and other risk factors for developing symptomatic COVID-19 vs asymptomatic SARS-CoV-2 infection: a case-control study from western Rajasthan, India

Suman Saurabh  1 , Mahendra Kumar Verma  1 , Vaishali Gautam  1 , Nitesh Kumar  1 , Vidhi Jain  2 , Akhil Dhanesh Goel  1 , Manoj Kumar Gupta  1 , Prem Prakash Sharma  1 , Pankaj Bhardwaj  1 , Kuldeep Singh  3 , Vijaya Lakshmi Nag  2 , Mahendra Kumar Garg  4 , Sanjeev Misra  5
Affiliations

Tobacco, alcohol use and other risk factors for developing symptomatic COVID-19 vs asymptomatic SARS-CoV-2 infection: a case-control study from western Rajasthan, India

Suman Saurabh et al. Trans R Soc Trop Med Hyg. .

Abstract

Background: Understanding risk factors of symptomatic coronavirus disease 2019 (COVID-19) vis-à-vis asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection, severe disease and death is important.

Methods: An unmatched case-control study was conducted through telephonic interviews among individuals who tested positive for SARS-CoV-2 in Jodhpur, India from 23 March to 20 July 2020. Contact history, comorbidities and tobacco and alcohol use were elicited using standard tools.

Results: Among 911 SARS-CoV-2-infected individuals, 47.5% were symptomatic, 14.1% had severe COVID-19 and 41 (4.5%) died. Older age, working outside the home, cardiac and respiratory comorbidity and alcohol use were found to increase the risk of symptomatic disease as compared with asymptomatic infection. Current tobacco smoking (odds ratio [OR] 0.46 [95% confidence interval {CI} 0.26 to 0.78]) but not smokeless tobacco use (OR 0.81 [95% CI 0.55 to 1.19]) appeared to reduce the risk of symptomatic disease. Age ≥60 y and renal comorbidity were significantly associated with severe COVID-19. Age ≥60 y and respiratory and cardiac comorbidity were found to predispose to mortality.

Conclusions: The apparent reduced risk of symptomatic COVID-19 among tobacco smokers could be due to residual confounding owing to unknown factors, while acknowledging the limitation of recall bias. Cross-protection afforded by frequent upper respiratory tract infection among tobacco smokers could explain why a similar association was not found for smokeless tobacco use, thereby being more plausible than the 'nicotinic hypothesis'. Those with comorbidities and age ≥60 y should be prioritized for hospital admission.

Keywords: COVID-19; alcohol; case-control; cross-protection; nicotine hypothesis; tobacco.

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Figures

Figure 1.
Figure 1.
Location of the All India Institute of Medical Sciences and the approximate catchment area of Jodhpur and surrounding districts in western Rajasthan, India. (Modified from source file https://commons.wikimedia.org/wiki/File:India_districts_map.svg, Creative Commons Attribution-Share Alike 4.0 International license).
Figure 2.
Figure 2.
Flowchart of recruitment of SARS-CoV-2-infected individuals for the case–control study, their clinical severity and outcomes.
See this image and copyright information in PMC

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