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

Table 3 Main results for endpoint: Admitted to intensive care unit

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)	1.57 (1.14-2.17)	0.87 (0.67-1.12)	0.94 (0.60-1.48)	1.55 (1.00-2.42)	1.13 (0.82-1.54)	1.40 (1.09-1.80)
		n	7	6	5	5	8	8
	C	EE (95%CI)	1.68 (1.15-2.46)	0.85 (0.77-0.94)	0.61 (0.11-3.36)	1.58 (0.97-2.57)	1.14 (0.54-2.41)	1.30 (0.74-2.31)
		n	2	2	1	1	3	3
	U	EE (95%CI)	1.42 (0.94-2.14)	0.94 (0.57-1.57)	0.98 (0.60-1.60)	1.55 (0.91-2.65)	0.98 (0.60-1.60)	1.42(0.94-2.14)
		n	4	4	4	4	4	4
All estimates	U	EE (95%CI)	1.52 (1.04-2.22)	1.03 (0.56-1.88)	0.92 (0.60-1.43)	1.68 (1.05-2.68)	1.11 (0.62-2.00)	1.61 (1.13-2.29)
		n	5	6	5	5	6	6
Population = hospitalized with COVID-194
Best-adjusted	All	EE (95%CI)	1.10 (0.99-1.22)	0.90 (0.72-1.12)	0.88 (0.72-1.08)	1.21 (0.99-1.47)	1.02 (0.87-1.21)	1.11 (0.98-1.25)
		n	9	9	6	6	14	14
	C	EE (95%CI)	1.01 (0.88-1.16)	0.80 (0.61-1.04)	0.81 (0.61-1.07)	1.07 (0.92-1.24)	0.81 (0.61-1.07)	1.01 (0.88-1.16)
		n	1	1	1	1	1	1
	U	EE (95%CI)	1.22 (1.04-1.43)	1.09 (0.93-1.27)	0.96 (0.70-1.31)	1.30 (1.00-1.70)	1.16 (1.05-1.28)	1.19 (1.08-1.30)
		n	8	7	5	5	12	12
All estimates	U	EE (95%CI)	1.20 (1.09-1.32)	1.00 (0.87-1.13)	0.89 (0.74-1.06)	1.28 (1.10-1.48)	1.05 (0.95-1.17)	1.14 (1.04-1.24)
		n	9	9	6	6	14	14

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

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

³For population = positive, the results are from eight studies. Six provided odds ratio (OR)s and two relative risk (RR)s;

⁴For population = hospitalized, the results are from 14 studies. Twelve provided ORs and two RRs. COVID-19: Coronavirus disease 2019; CI: Confidence interval.