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

Table 9 Summary of results from meta-analyses¹

Endpoint	Population	Smoking index = closest to current smoking			Smoking index = closest to ever smoking
		Best estimate2	Comorbidity adjusted3	Unadjusted4	Best estimate2	Comorbidity adjusted3	Unadjusted4
Positive	General	0.78 (0.57-1.06)5	0.96 (0.42-2.17)	0.56 (0.42-0.75)5	0.89 (0.73-1.09)	1.10 (0.70-1.72)	0.65 (0.55-0.77)
Positive	Tested	0.55 (0.47-0.65)	0.58 (0.43-0.80)	0.55 (0.45-0.67)	0.70 (0.63-0.77)	0.77 (0.64-0.92)	0.67 (0.58-0.78)
Hospitalized	Positive	1.31 (1.12-1.54)	0.96 (0.79-1.18)	1.44 (1.03-2.01)	1.38 (1.17-1.63)	0.93 (0.80-1.08)	1.71 (1.24-2.36)
ICU admission	Positive	1.13 (0.82-1.54)	1.14 (0.54-2.41)	0.98 (0.60-1.60)	1.40 (1.09-1.80)5	1.30 (0.74-2.31)	1.42 (0.94-2.14)
ICU admission	Hospitalized	1.02 (0.87-1.21)	0.81 (0.61-1.07)	1.16 (1.05-1.28)	1.11 (0.98-1.25)	1.01 (0.88-1.16)	1.19 (1.08-1.30)
Mechanically ventilated	Hospitalized	1.08 (0.86-1.36)	0.99 (0.77-1.29)5	1.16 (0.80-1.67)	1.11 (0.92-1.35)	1.04 (0.79-1.36)5	1.24 (0.99-1.54)
Severe	Positive	1.10 (0.97-1.25)5	1.02 (0.88-1.18)	1.35 (0.95-1.92)	1.10 (0.97-1.25)5	1.02 (0.88-1.18)	1.30 (0.94-1.79)
Severe	Hospitalized	1.08 (0.94-1.25)	1.23 (0.46-3.27)	1.17 (0.99-1.37)	1.09 (0.98-1.22)	1.35 (0.66-2.75)	1.14 (1.06-1.23)
Died	Positive	1.08 (0.82-1.42)	0.96 (0.92-1.01)	1.59 (1.40-1.80)	1.34 (0.96-1.86)	0.97 (0.93-1.02)	2.07 (1.12-3.82)
Died	Hospitalized	1.27 (1.08-1.49)5	1.09 (0.84-1.40)	1.52 (1.22-1.91)	1.42 (1.22-1.65)	1.12 (0.91-1.39)	1.79 (1.47-2.19)

¹See also Tables 1 to 6 for further details. Data shown are random-effects estimates with 95% confidence interval.

²Best estimates based on, respectively, 7, 17, 22, 8, 14, 15, 8, 10, 8 and 25 effect estimates (total 134).

³Comorbidity adjusted estimates based on, respectively, 3, 5, 8, 3, 1, 7, 1, 2, 4 and 10 (total 44).

⁴Unadjusted estimates based on, respectively, 3, 11, 11, 4, 12, 7, 5, 6, 3 and 13 (total 75). The unadjusted results shown are based only on those included in the best estimates;

⁵Significant publication bias (P < 0.05). ICU: Intensive care unit.