Successful Cessation Programs that Reduce Comorbidity may Explain Surprisingly Low Smoking Rates among Hospitalized COVID-19 Patients

Abstract

Recent, non-peer-reviewed reports and meta-analyses suggest that smoking may reduce the risk of hospitalization with COVID-19, because the prevalence of smoking among hospitalized COVID-19 is less than that of the general population. However, there are two alternative classes of explanations for this phenomenon. Class (1) is the failure to report, or to accurately record, smoking history during emergency hospital admissions and other interviews. Face-to-face interviews can introduce bias into the responses to attitudinal and behavioral questions not present in the self-completion interviews typically used to measure smoking prevalence in the general population. Subjects in face-to-face interviews may be unwilling to admit socially undesirable behavior and attitudes under direct questioning. For example, urine testing of hospitalized patients for cotinine showed that smokers were under-counted by 37% because incoming patients failed to inform staff about their smoking behavior. Class (2), various types of “reverse” causation, including a pre-disposition to avoid smoking among COVID-19 patients with tobacco-related comorbidities, may also contribute to the difference between smoking prevalence in the COVID-19 and general population. Patient cohorts hospitalized with COVID-19 may be less prone to use tobacco than the general population. A potentially robust “reverse causation” hypothesis for reduced prevalence of smokers in the COVID-19 population is enrichment of patients in the population with serious comorbidities that have previously motivated them to quit smoking. We ask whether this “smoking cessation” mechanism accounts for a detectable fraction of the reduced prevalence of smokers in the COVID-19 population. Testing this hypothesis will require a focused research program.