Table 1 The impact of smoking on the severity and mortality of COVID-19 patients in the different meta-analysis studies (> 10 studies)

1

Roengrudee Patanavanich

28 April 2020

19 papers (16 from China, 1 from Korea, and 2 from the United States)

11,590 patients:

Smoking is a risk factor for COVID-19 progression (OR 1.91).

[348]

2

Huimei Zhang

1 February 2021

109 articles (27 USA, 50 china, and 32 other countries)

517,020 patients

• Smoking elevated the risk of ICU admission and death in patients with COVID-19, but was not relevant to mechanical ventilation.

• Former smokers had a risk of progressing COVID-19 severity compared with current smokers. Current smokers were significantly associated with the severity of COVID-19 compared with non-smokers.

[349]

3

Adinat Umnuaypornlert

12 December 2020

40 studies (19 China, 1 Kuwait, 1 Korea, 1 Mexico, 1 Japan, 2 Spain, 3 Italy, and 12 USA)

369,287 patients

Smoking, even current smoking or former smoking, significantly enhances the risk of COVID-19 severity and death.

[350]

4

Rohin K. Reddy

Between 1 December 2019 and 2 June 2020

47 studies (32 China, 10 USA, 2 Italy, 1 UK, 2 International)

32, 849 patients

Current smoking is risk factor for disease progression, severity and mortality in hospitalized patients with COVID-19.

[351]

5

Qianwen Zhao

Between December 2019 and 22 March 2020

11 studies (11 china)

2002 patients

COPD and current smoking could develop severity of COVID-19.

[352]

6

Tao Zhang

Between 1 January 2020 and 10 April 2020

16 studies (16 china)

1,172 severe patients and 2,803 non-severe patients

• The prevalence of former smokers was higher in severe patients as compared to non-severe ones.

• The COVID-19 severity could be assessed by radiologic and laboratory findings, and smoking history

[353]

7

Linwen Zeng

Between 1 December 2019 and 2 May 2020

17 studies (16 China, 1 USA)

5,726 confirmed cases

Smoking did not enhance the risk of cardiovascular disease in COVID-19 patients in this study (probably due to small sample size, 3 studies, and large heterogeneity).

[354]

8

Jingyuan Xie

Between 1 January 2020 and 18 March 2020

90 studies (87 China, 1 Australia, 1 Singapore)

16,526 patients

Male gender, history of smoking, and comorbidities might affect the prognosis of COVID-19 patients.

[355]

9

Guiling Xiang

Between 1 December 2019 and 10 June 2020

20 studies

15,408 patients

Current smoking and elderly patients, aged 60 years old or over, are related with a higher risk of in-hospital death.

[356]

10

E. H. Taylor

Between 1 January 2020 and 6 December 2020

58 studies (15 China, 7 USA, 6 Spain, 3 UK, 2 Africa, 25 other countries)

44,305 patients

Increasing age, smoking, pre-existing comorbidities, and the host response to COVID-19 disease were associated with mortality.

[357]

11

David Simons

25 August 2020

32 studies

Not reported

In comparison with never smokers, current smokers seem to be at decreased risk of SARSCoV-2 infection whilst former smokers seem to be at elevated risk of hospitalisation, enhanced COVID-19 severity and mortality.

[358]

12

Angelo Silverio

27 April 2020

45 studies (35 China, 6 USA, and 4 other countries)

18,300 patients

• Male and smoking did not significantly influence mortality.

• Older age and diabetes are related to greater risk of in-hospital mortality in COVID-19 patients

[359]

13

Saeed Shoar

Between 20 December 2019 and 15 March 2020

12 studies (12 China)

1,845 patients

Smoking and co-morbidities (hypertension, diabetes mellitus, cardiovascular diseases) are associated with COVID-19 mortality.

[360]

14

Changcheng Shi

Between 1 December 2019 and 29 April 2020

27 studies (24 China, 2 USA, and 1 Italy)

23,860 patients

Older age, sex (male), smoking (current smokers), pre-existing comorbidities (chronic kidney, respiratory, and cardio-cerebrovascular diseases), some symptoms (dyspnea), and some abnormal laboratory indicators (inflammation and coagulation markers) were associated with COVID-19 mortality.

[361]

15

Arthur Eumann Mesas

Between December 2019 and 27 July 2020

60 studies in 13 countries (31 China, 13 USA, 16 other countries)

51,225 patients

There was a greater mortality risk from hospital COVID-19 patients for dyspnoea

(pooled OR = 2.5), smoking (pooled OR = 1.6) and some comorbidities and laboratory parameters.

[362]

16

You Li

Between January and May 2020

40 studies (18 China, 10 USA, 5 Italy, 7 other countries)

Not reported

• Male gender, older age, obesity, diabetes and chronic kidney diseases were associated with elevated risks for COVID-19 mortality.

• There was no elevated risk of mortality for some factors such as COPD, cancer, or current smoker (probably because of limited data on every of these factors)

[363]

17

Xinyang Li

Between December 2019 and February 2021

41 studies (30 China, 3 Korea, 2 USA, 6 other countries)

21,060 patients

Severe COVID-19 patients were related to older age, male sex, obesity, history of smoking, hypertension, diabetes, coronary heart disease, chronic kidney disease (CKD), cerebrovascular disease, COPD, malignancy, and chronic liver disease.

[364]

18

Jia Li

Between December 2019 and 14 April 2020

12 studies (12 China)

2,445 patients

Smoking history and comorbidities such as COPD, diabetes, hypertension, coronary heart disease, cerebrovascular diseases, and malignancy were risk factors for severity of COVID-19.

[365]

19

Zohra S Lassi

Between December 2019 and February 2021

62 studies (from 44 countries of the six continents)

31,016 pregnant women

• Older pregnant women (> 35 years), obesity, smoking, diabetes and pre-eclampsia could increase the risk of severe COVID-19.

• Severe COVID-19 women increased the risk of preterm birth.

[366]

20

Antonios Karanasos

Between 1 September 2019 and 4 May 2020

22 studies (20 China, 2 USA)

7,171 patients

The risk of severe COVID-19 was significantly greater among smokers, especially in younger patients without diabetes.

[367]

21

Shiwei Kang

Between 1 Jan and 6 October 2020

21 studies (17 China, 1 USA, 1 Japan, 1 England, 1 Italy)

7,041 patients

• Smoking history increased the mortality of COVID-19 patients (OR = 1.91).

• Cardiovascular disease enhanced the severity (OR = 2.87) and mortality (OR = 3.05) of COVID-19 patients.

[368]

22

Ian Huang

25 March 2020.

23 studies (22 China and 1 Japan)

3,099 patients

• Age was associated with lymphopenia in COVID-19 patients (lymphopenia was higher in younger patients compared with older ones).

• There was no association between lymphopenia and gender, cardiac comorbidity, hypertension, diabetes mellitus, COPD, and smoking.

[369]

23

Hongjie Hou

Between 15 January 2020 and 12 April 2021

73 articles (30 USA, 6 Italy, 7 England, 6 China, 6 Mexico, 4 Spain, and 14 other countries)

863,313 patients

Smoking elevated the mortality risk in COVID-19 patients.

[370]

24

Askin Gülsen

Between December 2019 and 15 April 2020

16 studies (14 China, 1 USA, 1 unknown)

11,322 patients

Current smoking was significantly associated with severe COVID-19.

[341]

25

Stefano Figliozzi

24 April 2020

49 studies (from China, Italy, Spain, France, Germany, Netherlands, Iran, and South Korea, USA)

587 790 and 602 234 cases statistics for age and sex.

• Older age, male gender, some co-morbidities such as acute cardiac or kidney injury, lymphocytopenia, and some laboratory biomarkers (D-dimer) elevated the risk of mortality in COVID-19 patients.

• Smoking was not a predictor of the risk of death, it could increase adverse outcomes in COVID-19 patients.

[371]

26

Zhaohai Zheng

20 March 2020

13 studies (13 china)

3,027 patients

• The proportion of male, aged more than 65, smoking patients were statistically significant higher in critical/mortal group in comparison with

the non-critical group.

[372]

27

Diana C. Sanchez-Ramirez

Between 1 January and 15 April 2020

22 studies (21 China and 1 USA)

13,184 patients

• The incidence of pulmonary diseases and smoking (current and former smoking) were significantly related to severe COVID-19 outcomes.

[373]

28

Alqahtani, J. S., et al. (2020)

March 24, 2020

15 studies (14 China, 1 United States)

2473 patients

• Increased severity (63%) and mortality (60%) in infected COPD patients.

• Increased severity in infected current (22%) and ex-smokers (46%).

[342]