Previous studies have explored several risk factors for coronavirus disease 2019 (COVID-19) severity, but there is still a lack of association with smoking. Our study aims to find out the association between smoking and COVID-19 severity.

This comparative study was conducted among hospitalized severely and critically ill COVID-19 patients, as well as asymptomatic, mild, and moderate patients from the list of the city corporation (Dhaka, Bangladesh), as confirmed by reverse-transcription polymerase chain reaction (RT-PCR). A total of 2022 adults aged ≥18 years were enrolled in this study.

The mean age of the patients was 41.17 years; 66.96% of the patients were male, 57.02% were aged above 35 years, and 81.50% of the patients had ever been married; and 33.09% cases were mild and 14.99% were severe. Among the patients, 29.4% were ever-smokers. Smoking status, duration, and frequency, and the presence of comorbidities were significantly associated with COVID-19 severity (p<0.001). Ever-smokers were 1.35 times (95% CI: 0.74–2.45), 1.30 times (95% CI: 0.58–2.87), and 2.45 times (95% CI: 1.07–5.61) more likely to be mild, severe, and critical cases in comparison to non-smokers.

This study revealed a strong association between smoking and COVID-19 severity that calls for mass awareness and cessation campaigns from governments and voluntary organizations.