Smoking has been found to significantly increase the hospitalization and mortality rates of COVID-19 patients. Previous studies did not always show this correlation because they only considered patients’ current smoking habits, rather than their cumulative smoking dose. However, a study of health data from China in March 2020 provided evidence that smoking increases the risk of severe COVID-19 illness. The University of California (UCLA) identified smoking as a cause of inhibiting the formation and maturation of respiratory stem cells. While some studies have shown conflicting results, the cumulative smoking dose is crucial in determining the risk of severe COVID-19 illness.
In response to these conflicting studies, scientists at the Cleveland Clinic have been recording information on the cumulative smoking dose of COVID-19 patients since March 2020. Of the 7,102 patients recorded, 910 were former smokers and 172 were current smokers. 341 of these patients had a cumulative smoking dose of at least 30 pack-years. According to an analysis of health data published in the JAMA Internal Medicine journal, the hospitalization rate of this group was 4.65 times higher than that of non-smokers. They also required intensive care treatment 2.11 times more often and had a 6.2 times higher risk of death. However, the increased risk is mainly due to smoking-related comorbidities.
The higher risk of severe COVID-19 illness among smokers is mainly due to smoking-related comorbidities. 85.5% of the patients had arterial hypertension, 47.2% had emphysema or COPD, 43.1% had coronary heart disease, 32.3% had heart failure, and 30.8% had a history of or current cancer. 22.9% had asthma. When factors such as age, gender, and ethnicity were taken into account, the risk of hospitalization, intensive care treatment, and death from COVID-19 was still significantly higher for those with a cumulative smoking dose of more than 30 pack-years. Therefore, it is crucial to consider the cumulative smoking dose when assessing the risk of severe COVID-19 illness among smokers.
