The Impact of Smoking on COVID-19 Analyzed by Hierarchical Linear Model

COVID-19 has been of great concern since it broke out. Many countries have put more effort into securing vaccines and therapeutic medicines. In the meantime, there has been a large number of scholarly efforts in figuring out the relationship between smoking and new coronary pneumonia. This study firstly collected daily data (the number of people hospitalized with new coronary pneumonia, severe cases, and the number of people double-vaccinated against new coronary pneumonia in various countries or regions) and annual data (the human development index and smoking rate of each country or region). We collected data from 160 countries from the Our Data World database. The time is for January 1, 2020 through June 30, 2022. We divided daily and annual data into the first-level and second-level data. Finally, we checked the relationship between smoking and COVID-19 in a Hierarchical Linear Model (HLM). The result shows that smoking raises the number of new cases of infection and death among people fully vaccinated per hundred. There is a partial mediating effect of new cases smoothed per million over new deaths smoothed per million. Smoking significantly increases the effect of new cases smoothed per million over new deaths smoothed per million. Our findings have high generalizability around the world.