The Effect of Smoking on COVID-19 Symptom Severity: Systematic Review and Meta-Analysis

Table 1

Newcastle-Ottawa scale for quality assessment and risk of bias.

Study	Year	Case selection (max. 4)	Comparability (max. 2)	Exposure/outcome (max. 3)	Total score
CDC report [4]	2020				7
Chen Q [10]	2020				6
Feng Y [11]	2020				6
Goyal P [12]	2020		—		5
Guan WJ [13]	2020				6
Liu W [14]	2020				7
Mo P [15]	2020				6
Qi D [16]	2020				7
Shi Y [17]	2020				5
Wang R [18]	2020				6
Wan S [19]	2020				7
Yang X [20]	2020				8
Yu X [21]	2020				7
Zhang JJ [22]	2020				7
Zhang R [23]	2020				6
Zhou F [24]	2020				7