Systematic review with meta-analysis of the epidemiological evidence in Europe, Israel, America and Australasia on smoking and COVID-19

Table 2 Main results for endpoint: Hospitalized with coronavirus disease 2019

Selection of estimates1		Statistic2	Ever vs never	Current vs non-current	Current vs never	Former vs never	Closest to current	Closest to ever
Population = positive for COVID-193
Best-adjusted	All	EE (95%CI)	1.34 (1.13-1.60)	1.00 (0.86-1.16)	1.05 (0.84-1.32)	1.31 (0.93-1.85)	1.31 (1.12-1.54)	1.38 (1.17-1.63)
		n	19	13	11	11	22	22
	C	EE (95%CI)	1.00 (0.76-1.32)	0.90 (0.76-1.07)	0.82 (0.52-1.30)	0.87 (0.67-1.12)	0.96 (0.79-1.18)	0.93 (0.80-1.08)
		n	6	6	4	4	8	8
	U	EE (95%CI)	1.53 (1.14-2.06)	1.03 (0.75-1.41)	1.13 (0.81-1.59)	1.77 (1.04-3.04)	1.44 (1.03-2.01)	1.71 (1.24-2.36)
		n	10	6	6	6	11	11
All estimates	U	EE (95%CI)	1.64 (1.41-1.91)	0.97 (0.71-1.32)	1.20 (1.01-1.42)	1.75 (1.35-2.27)	1.47 (1.21-1.77)	1.72 (1.46-2.02)
		n	18	13	11	11	21	21

¹Best-adjusted = estimates for a study selected in preference order of adjustment (C = comorbidities, D = demographics only, U = unadjusted, P = includes post-COVID responses).

²EE = effect estimate from random-effects meta-analysis.

³The results are from 21 studies, one study providing sex-specific estimates. Nineteen studies provide odds ratio (OR)s, one relative risk (RR)s and hazard ratios, and one ORs and RRs. COVID-19: Coronavirus disease 2019; CI: Confidence interval.