Table 1: Characteristics of the studies included in the analysis.

Publication Date	Authors	Journal	Location	Type of Study	No. participants	Males	Smokers	Mortality
24032020	Emami A; et al. [13]	Arch Acad Emerg Med 2020;8(1): e35	Shiraz, Iran	Systematic review and meta-analysis	3403	57,97%	7.63%	&
21022020	Lupia T; et al. [15]	Viruses. 2020 Feb; 12(2): 135.	Turin, Italy	Systematic review	76993	56%	2%	&&
2020	Harris C; et al. [14]	J Global Health 2002 Jun 10(1):011001	Edinburgh, UK	Systematic review				&&
20032020	Vardavas CI, et al. [12]	Tob Induc Dis 2020; 18:20	Boston, USA	Systematic review	1099		&&&	Uninformed
2020	Guan W; et al.[19]	Eur Respir J 2020 Mar 26:2000547	Wuhan, China	Retrospective study	1590	59,30%	3,10%	&*
29012020	Chen N; et al. [17]	Lancet 2020; 15- 21Feb;395(10223):507-513	Wuhan, China	Retrospective study	99	67,67%	11%	58%
27032020	Guo T; et al. [1]	J Glob Antimicrob Resist 2020 Mar 7	Wuhan, China	Retrospective study	187	48,66%	10,38%	22,90%
21022020	Yang X; et al. [20]	Lancet respir Med 2020; Feb 28; 8(4): e26	Wuhan, China	Retrospective study	52	67,30%	3,84%	32%
2020	Shi Y; et al. [18]	Crit Care 2020; 24:108	Hangzhou, China	Retrospective study	487	53,18%	8,21%	61,50%
20032020	Brake SJ; et al. [16]	J. Clin. Med. 2020, 9(3), 841	Tasmania, Australia	Retrospective study				&**
18022020	Zhang J; et al. [21]	Allergy. 2020 Feb 19	Wuhan, China; Davos, Switzerland	Retrospective study	140	50,70%	1,40%	Uninformed

&: smoking was not directly related to increased mortality, but rather to the occurrence of more severe COVID-20 pictures; &&: It mentions smoking as a risk factor for deaths by COVID-19; &&&: 2.4 times (RR=2.4, 95% CI: 1.43-4.04) more likely to be admitted to the intensive care unit, need mechanical ventilation or die; &*: It refers to the association between the increase in the number of comorbidities and the increase in mortality and hospitalization outcomes by COVID-19; &**: It refers to the association of men, elderly and the presence of comorbidities as unfavourable factors for mortality and hospitalization outcomes by COCID-19.