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

Table 4 Main results for endpoint: Mechanically ventilated

Selection of estimates1		Statistic2	Ever vs never	Current vs non-current	Current vs never	Former vs never	Closest to current	Closest to ever
Population = hospitalized for COVID-193
Best-adjusted	All	EE (95%CI)	1.05 (0.88-1.25)	1.11 (0.72-1.71)	1.12 (0.60-2.09)	1.16 (0.87-1.55)	1.08 (0.86-1.36)	1.11 (0.92-1.35)
		n	12	8	5	5	15	15
	C	EE (95%CI)	1.04 (0.79-1.36)	1.94 (0.40-9.49)	2.77 (0.28-27.2)	2.43 (0.32-18.5)	0.99 (0.77-1.29)	1.04 (0.79-1.36)
		n	7	2	2	2	7	7
	U	EE (95%CI)	1.06 (0.94-1.21)	1.12 (0.60-2.09)	0.76 (0.59-0.98)	1.10 (0.96-1.27)	1.16 (0.80-1.67)	1.24 (0.99-1.54)
		n	5	5	3	3	7	7
All estimates	U	EE (95%CI)	1.07 (0.92-1.26)	1.10 (0.80-1.51)	1.09 (0.60-1.95)	1.12 (0.98-1.28)	1.12 (0.98-1.38)	1.17 (1.00-1.37)
		n	10	8	5	5	13	13

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

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

³Fourteen studies provided results, one providing estimates for two age groups. Thirteen studies provided odds ratios and one relative risks. COVID-19: Coronavirus disease 2019; CI: Confidence interval.