UCSF

Background

Research investigating the association between cigarette smoking and COVID-19 outcomes has yielded mixed results, often overlooking cannabis use. This study examined the association between cigarette smoking and COVID-19 hospitalization with consideration of cannabis use.

Methods

We used electronic health record data from adult patients with COVID-19 (2/1/2020 to 2/3/2022) at a northern California academic medical center. The outcome was COVID-19 hospitalization. We conducted three multivariable logistic models to examine the relationship between cigarette smoking and hospitalization. Model 1 included cigarette smoking status and other covariates; Model 2 added cannabis use status to Model 1; Model 3 added interaction term of cigarette and cannabis use to Model 2, followed by a post-hoc analysis.

Results

Of the 14,440 patients, 8.5 % had COVID-19 hospitalization, 4.9 % and 24.1 % currently and formerly smoked cigarettes, respectively; 7.2 % currently used cannabis, 62.8 % had unknown cannabis use status. Both current and former cigarettes smoking were associated with hospitalization (Models 1-2). In Model 3, the cigarette-cannabis interaction was significant. Former cigarette smoking had higher odds for hospitalization (adjusted odds ratio [AOR] = 1.36; 95 % confidence interval [CI] 1.09-1.70) only among people who did not currently use cannabis. Current cigarette smoking yielded higher odds of hospitalization (AOR = 1.47; 95 % CI 1.02-2.12) among people whose cannabis use was unknown. Cigarette smoking status was not associated with hospitalization among people who currently used cannabis.

Conclusions

Cigarette smoking's associations with COVID-19 hospitalization varied by cannabis use. Future research should include both cigarette and cannabis use in understanding risk factors for COVID-19 outcomes.