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

Table 6 Main results for endpoint: Died

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 with COVID-193
Best-adjusted	All	EE (95%CI)	1.42 (1.19-1.70)	0.99 (0.89-1.10)	1.12 (0.98-1.29)	1.61 (1.34-1.92)	1.27 (1.08-1.49)	1.42 (1.22-1.65)
		n	18	10	10	10	25	25
	C	EE (95%CI)	1.07 (0.82-1.38)	0.64 (0.12-3.35)	1.02 (0.70-1.49)	1.15 (1.02-1.29)	1.09 (0.84-1.40)	1.12 (0.91-1.39)
		n	8	2	3	3	10	10
	U	EE (95%CI)	1.78 (1.40-2.26)	0.95 (0.77-1.16)	1.18 (0.91-1.52)	1.92 (1.48-2.50)	1.52 (1.22-1.91)	1.79 (1.47-2.19)
		n	9	6	6	6	13	13
All estimates	U	EE (95%CI)	1.59 (1.37-1.83)	1.00 (0.88-1.13)	1.12 (0.97-1.29)	1.80 (1.48-2.17)	1.33 (1.18-1.51)	1.58 (1.39-1.78)
		n	15	10	9	9	20	20
Population = with COVID-194
Best-adjusted	All	EE (95%CI)	1.41 (0.93-2.14)	0.96 (0.92-1.01)	0.98 (0.72-1.32)	1.61 (0.79-3.29)	1.08 (0.82-1.42)	1.34 (0.96-1.86)
		n	7	6	5	5	8	8
	C	EE (95%CI)	0.99 (0.87-1.13)	0.96 (0.92-1.01)	0.85 (0.67-1.07)	1.04 (0.91-1.19)	0.96 (0.92-1.01)	0.97 (0.93-1.02)
		n	3	4	3	3	4	4
	U	EE (95%CI)	2.07 (1.12-3.82)	0.93 (0.60-1.46)	1.49 (0.94-2.36)	2.70 (1.11-6.58)	1.59 (1.40-1.80)	2.07 (1.12-3.82)
		n	3	2	2	2	3	3
All estimates	U	EE (95%CI)	2.04 (1.39-3.02)	1.06 (0.39-2.90)	1.07 (0.72-1.58)	2.58 (1.31-5.07)	1.52 (0.89-2.60)	2.22 (1.51-3.27)
		n	5	5	4	4	6	6

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

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

³For population = hospitalized, the results are from twenty four studies, one providing age-specific estimates. Seventeen provided only odds ratio (OR)s, two only hazard ratio (HR)s, two only relative risk (RR)s, and three RRs and HRs, one of these also providing ORs.

⁴For population = with COVID-19, the results are from eight studies, six providing ORs, one RRs and one HRs and RRs. COVID-19: Coronavirus disease 2019; CI: Confidence interval.