Protective Effect of Smoking against Covid-19

1. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China

https://www.thelancet.com/journals/lancet/article/PIIS0140-6736(20)30183-5/fulltext
Published: 2020-01-24
Location of sample: China (Wuhan)
Sample size: 41
Authors:
- Chaolin Huang (Jin Yin-tan Hospital, Wuhan, China)
- Yeming Wang (Department of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases, China-Japan Friendship Hospital, Beijing, China; Institute of
  Respiratory Medicine, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China; Department of Respiratory Medicine, Capital Medical University, Beijing, China)
- Xingwang Li (Clinical and Research Center of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing, China)
- Lili Ren (NHC Key Laboratory of Systems Biology of Pathogens and Christophe Merieux Laboratory, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China)
- Jianping Zhao (Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China)
- Yi Hu (Tongji Hospital and Department of Pulmonary and Critical Care Medicine, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China)
- Li Zhang (Jin Yin-tan Hospital, Wuhan, China)
- Guohui Fan (Department of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases; Institute of Clinical Medical Sciences, China-Japan Friendship Hospital,
  Beijing, China; Institute of Respiratory Medicine, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China)
- Jiuyang Xu (Tsinghua University School of Medicine, Beijing, China)
- Xiaoying Gu (Department of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases; Institute of Clinical Medical Sciences, China-Japan Friendship
  Hospital, Beijing, China; Institute of Respiratory Medicine, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China)
- Zhenshun Cheng (Department of Respiratory medicine, Zhongnan Hospital of Wuhan University, Wuhan, China)
- Ting Yu (Jin Yin-tan Hospital, Wuhan, China)
- Jiaan Xia (Jin Yin-tan Hospital, Wuhan, China)
- Yuan Wei (Jin Yin-tan Hospital, Wuhan, China)
- Wenjuan Wu (Jin Yin-tan Hospital, Wuhan, China)
- Xuelei Xie (Jin Yin-tan Hospital, Wuhan, China)
- Wen Yin (Tongji Hospital and Department of Pulmonary and Critical Care Medicine, The Central Hospital of Wuhan, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China)
- Hui Li (Department of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases, China-Japan Friendship Hospital, Beijing, China; Institute of Respiratory
  Medicine, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China; Department of Respiratory Medicine, Capital Medical University, Beijing, China)
- Min Liu (Institute of Clinical Medical Sciences and Department of Radiology, China-Japan Friendship Hospital, Beijing, China)
- Yan Xiao (NHC Key Laboratory of Systems Biology of Pathogens and Christophe Merieux Laboratory, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China)
- Hong Gao (NHC Key Laboratory of Systems Biology of Pathogens and Christophe Merieux Laboratory, Institute of Pathogen Biology and Institute of Laboratory Animal Science, Chinese Academy of Medical Sciences and Peking Union
  Medical College, Beijing, China)
- Li Guo (NHC Key Laboratory of Systems Biology of Pathogens and Christophe Merieux Laboratory, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China)
- Jungang Xie (Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China)
- Guangfa Wang (Department of Pulmonary and Critical Care Medicine, Peking University First Hospital, Beijing, China)
- Rongmeng Jiang (Clinical and Research Center of Infectious Diseases, Beijing Ditan Hospital, Capital Medical University, Beijing, China)
- Zhancheng Gao (Department of Pulmonary and Critical Care Medicine, Peking University People’s Hospital, Beijing, China)
- Qi Jin (NHC Key Laboratory of Systems Biology of Pathogens and Christophe Merieux Laboratory, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China)
- Jianwei Wang (NHC Key Laboratory of Systems Biology of Pathogens and Christophe Merieux Laboratory, Institute of Pathogen Biology, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, China)
- Bin Cao (Department of Pulmonary and Critical Care Medicine, Center of Respiratory Medicine, National Clinical Research Center for Respiratory Diseases, China-Japan Friendship Hospital, Beijing, China; Institute of Respiratory
  Medicine, Chinese Academy of Medical Sciences, Peking Union Medical College, Beijing, China; Department of Respiratory Medicine, Capital Medical University, Beijing, China; Tsinghua University-Peking University Joint Center for
  Life Sciences, Beijing, China )
Synopsis:
- A small study of 41 hospitalized COVID-19 patients (30 male, 11 female). According to data from 2020¹, 24.7% of the population of China smoke tobacco (47.6% of males, 1.8% of females). Therefore, in this study, we expect to find a total of approximately 14 smokers (14 male, 0 female). However, of the patients studied, only three patients were smokers (7%) while 38 were non-smokers (93%). None of the three smoking cases were serious. Thus, this study indicates that smokers in China are significantly less likely to be hospitalized due to COVID-19.

2. Clinical characteristics of 2019 novel coronavirus infection in China

https://www.medrxiv.org/content/10.1101/2020.02.06.20020974v1.full.pdf+html
https://www.nejm.org/doi/10.1056/NEJMoa2002032
Published: 2020-02-06 (re-published in New England Journal of Medicine 2020-04-30)
Location of sample: China
Sample size: 1,099
Authors:
- Wei-jie Guan (Guangzhou Institute of Respiratory Health)
- Zheng-yi Ni (Wuhan Jin-yintan Hospital)
- Yu Hu (Institute of Hematology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology)
- Wen-hua Liang (Department of thoracic oncology, The First Affiliated Hosptial of Guangzhou Medical University)
- Chun-quan Ou (State Key Laboratory of Organ Failure Research, Department of Biostatistics, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University)
- Jian-xing He (Department of thoracic surgery and oncology, The First Affiliated Hospital of Guangzhou Medical University)
- Lei Liu (Shenzhen Third Peoples Hospital, The Second Affiliated Hospital of Southern University of Science and Technology, National Clinical Research Center for Infectious Diseases)
  – Hong Shan (The Fifth Affiliated Hospital of Sun Yat-sen University)
- Chun-liang Lei (Guangzhou Eighth People’sospital, Guangzhou Medical University)
- David SC Hui (Department of Medicine & Therapeutics, The Chinese University of Hong Kong)
- Bin Du (Medical ICU, Peking Union Medical College Hospital, Peking Union Medical College and Chinese Academy of Medical Sciences)
- Lan-juan Li (State Key Laboratory for Diagnosis and Treatment of Infectious Diseases, National Clinical Research Center for Infectious Diseases, The First Affiliated Hospital, College of Medicine, Zhejiang University)
- Guang Zeng (Chinese Center for Disease Control and Prevention)
- Kowk-Yung Yuen (Department of Clinical Microbiology and Infection Control, The University of Hong Kong-Shenzhen Hospital, Shenzhen, Guangdong, People’s Republic of China; Department of Microbiology, Li Ka Shing Faculty of Medicine, The University of Hong Kong, Pokfulam)
- Ru-chong Chen (Department of Respiratory Disease, Guangzhou Institute of Respiratory Health)
- Chun-li Tang (Department of Respiratory Disease, Guangzhou Institute of Respiratory Health)
- Tao Wang (Department of Respiratory Disease, Guangzhou Institute of Respiratory Health)
- Ping-yan Chen (State Key Laboratory of Organ Failure Research, Department of Biostatistics, Guangdong Provincial Key Laboratory of Tropical Disease Research, School of Public Health, Southern Medical University)
- Jie Xiang (Wuhan Jin-yintan Hospital)
- Shi-yue Li (Department of Respiratory Disease, Guangzhou Institute of Respiratory Health)
- Jin-lin Wang (Department of Respiratory Disease, Guangzhou Institute of Respiratory Health)
- Zi-jing Liang (Department of Emergency Room, The First Affiliated Hospital of Guangzhou Medical University)
- Yi-xiang Peng (The Central Hospital of Wuhan)
- Li Wei (Wuhan No.1 Hospital, Wuhan Hospital of Traditional Chinese and Western Medicine)
- Yong Liu (Chengdu Public Health Clinical Medical Center)
- Ya-hua Hu (Huangshi Central Hospital of Edong Healthcare Group, Affiliated Hospital of Hubei Polytechnic University)
- Peng Peng (Wuhan Pulmonary Hospital)
- Jian-ming Wang (Tianyou Hospital Affiliated to Wuhan University of Science and Technology)
- Ji-yang Liu (Tianyou Hospital Affiliated to Wuhan University of Science and Technology)
- Zhong Chen (The Third People’s Hospital of Hainan Province)
- Gang Li (Huanggang Central Hospital)
- Zhi-jian Zheng (Wenling First People’s Hospital)
- Shao-qin Qiu (The Third People’s Hospital of Yichang)
- Jie Luo (Affiliated Taihe Hospital of Hubei University of Medicine)
- Chang-jiang Ye (Xiantao First People’s Hospital)
- Shao-yong Zhu (The People’s Hospital of Huangpi District)
- Nan-shan Zhong (Guangzhou Institute of Respiratory Health)
Synopsis:
- A study of 1,099 hospitalized COVID-19 patients from 552 hospitals in China (640 male, 459 female). According to data from 2020¹, 24.7% of the population of China smoke tobacco (47.6% of males, 1.8% of females). Therefore, in this study, we expect to find a total of approximately 312 smokers (304 male, 8 female). However, only 137 were current smokers (12.6%); 927 patients were never-smokers (85.4%) and 21 were former smokers (1.9%). Of those 137 current smokers, only 29 of the cases were considered severe. Thus, this study indicates that smokers in China are significantly less likely to be hospitalized due to (and also far less likely to develop severe symptoms from) COVID-19.

3. Clinical characteristics of 140 patients infected with SARSCoV-2 in Wuhan, China

https://onlinelibrary.wiley.com/doi/pdf/10.1111/all.14238
Published: 2020-02-17
Location of sample: China (Wuhan)
Sample size: 140
Authors:
- Jin-jin Zhang (Department of Allergology, Zhongnan Hospital of Wuhan University, Wuhan, China)
- Xiang Dong (Department of Allergology, Zhongnan Hospital of Wuhan University, Wuhan, China)
- Yi-yuan Cao (Department of Radiology, Zhongnan Hospital of Wuhan University, Wuhan, China)
- Ya-dong Yuan (Department of Respiratory and Critical Care Medicine, Second Hospital of Hebei Medical University, Shijiazhuang, China)
- Yi-bin Yang (Department of Respiratory and Critical Care Medicine, Zhongnan Hospital of Wuhan University, Wuhan, China)
- You-qin Yan (Department of Infectious Disease, No. 7 Hospital of Wuhan, Wuhan, China)
- Cezmi A. Akdis (Swiss Institute of Allergy and Asthma Research (SIAF), University of Zurich, Davos, Switzerland)
- Ya-dong Gao (Department of Allergology, Zhongnan Hospital of Wuhan University, Wuhan, China)
Synopsis:
- A study of 140 hospitalized COVID-19 patients in Wuhan, China (71 male, 69 female). According to data from 2020¹, 24.7% of the population of China smoke tobacco (47.6% of males, 1.8% of females). Therefore, in this study, we expect to find a total of approximately 34 smokers (33 male, 1 female). However, only two of the patients were current smokers (1.43%); 131 patients were never-smokers (93.57%) and only seven were former smokers (5%). Thus, this study indicates that smokers in China are significantly less likely to be hospitalized due to COVID-19.
Relevant excerpt(s):
- “The exact underlying causes of the lower incidence of COVID‐19 in current smokers are still unknown”

4. Clinical course and outcomes of critically ill patients with SARS-CoV-2 pneumonia in Wuhan, China: a single-centered, retrospective, observational study

https://www.thelancet.com/journals/lanres/article/PIIS2213-2600(20)30079-5/fulltext
Published: 2020-02-21
Location of sample: China (Wuhan)
Sample size: 52
Authors:
- Xiaobo Yang (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China; Jin Yin-tan Hospital, Wuhan, China)
- Yuan Yu (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- Jiqian Xu (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- Huaqing Shu (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- Jia’an Xia (Jin Yin-tan Hospital, Wuhan, China)
- Hong Liu (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China; Jin Yin-tan Hospital, Wuhan, China)
- Yongran Wu (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- Lu Zhang (Department of Critical Care Medicine, Xiangyang Central Hospital, Affiliated Hospital of Hubei University of Arts and Science, Hubei, China)
- Zhui Yu (Department of Critical Care Medicine, Renmin Hospital of Wuhan University, Wuhan, China)
- Minghao Fang (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China and Department of Critical Care Medicine, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China)
- Ting Yu (Jin Yin-tan Hospital, Wuhan, China)
- Yaxin Wang (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- Shangwen Pan (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- Xiaojing Zou (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- Shiying Yuan (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China)
- You Shang (Department of Critical Care Medicine, Institute of Anesthesiology and Critical Care Medicine, Union Hospital, Wuhan, China; Jin Yin-tan Hospital, Wuhan, China)
Synopsis:
- A study of 52 critically-ill hospitalized COVID-19 patients in Wuhan, China (35 male, 17 female). Only two of the patients were smokers (3.84%). According to data from 2020¹, 24.7% of the population of China smoke tobacco (47.6% of males, 1.8% of females). Therefore, in this study, we expect to find a total of approximately 16 smokers (16 male, 0 female). However, only two of the patients were smokers. Thus, this study indicates that smokers in China are far less likely to become critically ill due to COVID-19. It is also significant to note that of the 52 patients, 32 died and only 20 survived, including the two smokers.

5. Smoking, vaping and hospitalization for COVID-19

https://www.qeios.com/read/Z69O8A.13
Published: 2020-03-23 (Most recent update: 2020-04-04)
Location of sample: China
Sample size: 5,960
Authors:
- Konstantinos Farsalinos (University of West Attica, Athens, Greece)
- Anastasia Barbouni (University of West Attica, Athens, Greece)
- Raymond Niaura (New York University, New York, USA)
Synopsis:
- A meta-analysis of 13 Chinese studies including 5,960 hospitalized COVID-19 patients across China (Not all studies contained data on sex. Of the known distribution by sex, 3,286 were male, 2,673 were female). According to data from 2020¹, 24.7% of the population of China smoke tobacco (47.6% of males, 1.8% of females). However, the authors of this study cite more up-to-date data regarding smoking prevalence in China: 26.6% of the Chinese population smoke tobacco (50.5% of males, 2.1% of females) Using the authors’ figures, in this study, we expect to find a total of approximately 1,715 smokers (1,659 male, 56 female). However, only 450 of the hospitalized patients were current smokers (7.55%). Thus, this study indicates that smokers in China are significantly less likely to be hospitalized due to COVID-19.
Relevant excerpt(s):
- “No recommendation can be currently made concerning the effects of smoking on the risk of hospitalization for COVID-19. In fact, the consistently low prevalence of current smoking among Chinese patients with COVID-19 was further supported by the recent data recently released from the US CDC. From a total of 7162 patients in the US, only 1.3% were current smokers. low smoking prevalence was also observed among hospitalized non-ICU (2.1%) and ICU cases (1.1%), while the population smoking prevalence in the US is 13.8%. These observations raise a possible hypothesis that nicotine might reduce the risk for severe COVID-19. Hospitalization for COVID-19 will inevitably result in abrupt withdrawal of nicotine and its beneficial effect linked to this hypothesis in smokers or users of other nicotine products. This could, at least partly, explain the association between smoking and COVID-19 severity among hospitalized patients. Nicotine has been found to prevent acute lung injury in an animal ARDS model and has immunomodulatory effects. There is also evidence for an interaction between nicotine and the renin-angiotensin-aldosterone axis, although such interactions remain unclear. In any case, the observations of a consistently low prevalence of smoking among COVID-19 cases in China and the US, together with the potential mechanisms through which nicotine interacts with the inflammatory process and the renin-angiotensin-aldosterone axis involved in the development of COVID-19, warrant an urgent investigation of the clinical effects of pharmaceutical nicotine on COVID-19 susceptibility, progression and severity. The potential need to provide pharmaceutical nicotine products to smokers who experience an abrupt withdrawal of nicotine when hospitalized for COVID-19 or aim to follow medical advice to quit smoking to relieve underlying conditions that may increase vulnerability to serious or fatal symptoms should also be examined.”

6. Preliminary Estimates of the Prevalence of Selected Underlying Health Conditions Among Patients with Coronavirus Disease 2019 — United States, February 12–March 28, 2020

https://www.cdc.gov/mmwr/volumes/69/wr/mm6913e2.htm
Published: 2020-04-03
Location of sample: USA
Sample size: 7,162
Authors:
- Nancy Chow (US Centers for Disease Control and Prevention (CDC))
- Katherine Fleming-Dutra (US Centers for Disease Control and Prevention (CDC))
- Ryan Gierke (US Centers for Disease Control and Prevention (CDC))
- Aron Hall (US Centers for Disease Control and Prevention (CDC))
- Michelle Hughes (US Centers for Disease Control and Prevention (CDC))
- Tamara Pilishvili (US Centers for Disease Control and Prevention (CDC))
- Matthew Ritchey (US Centers for Disease Control and Prevention (CDC))
- Katherine Roguski (US Centers for Disease Control and Prevention (CDC))
- Tami Skoff (US Centers for Disease Control and Prevention (CDC))
- Emily Ussery (US Centers for Disease Control and Prevention (CDC))
Synopsis:
- A study of 7,162 COVID-19 patients across the USA (including both hospitalized and those not requiring hospitalization); no statistics were presented with regard to the distribution by sex. According to data from 2020¹, 17.25% of the population of the USA smoke tobacco (19.5% of males, 15.0% of females). Therefore, in this study, we expect to find a total of approximately 1,235 smokers. However, only 96 of the patients were current smokers (1.3%), and only 165 were former smokers (2.3%). Thus, this study indicates that smokers in the USA are significantly less likely to test positive for COVID-19. Whether this is due to smokers being less likely to contract SARS-CoV-2, or whether smokers are less likely to suffer severe enough symptoms to require testing/medical attention is unclear.
Relevant excerpt(s):
- “Finally, for some underlying health conditions and risk factors, including neurologic disorders, chronic liver disease, being a current smoker, and pregnancy, few severe outcomes were reported; therefore, conclusions cannot be drawn about the risk for severe COVID-19 among persons in these groups.”

7. Factors associated with hospitalization and critical illness among 4,103 patients with COVID-19 disease in New York City

https://www.medrxiv.org/content/10.1101/2020.04.08.20057794v1
https://www.bmj.com/content/369/bmj.m1966
Published: 2020-04-08 (re-published in The BMJ: 2020-05-22)
Location of sample: USA (New York City, NY)
Sample size: 1,999
Authors:
- Christopher M. Petrilli (Grossman School of Medicine, New York University, New York, NY USA)
- Simon A. Jones (Grossman School of Medicine, New York University, New York, NY, USA)
- Jie Yang (Grossman School of Medicine, New York University, New York, NY, USA)
- Harish Rajagopalan (Langone Health, New York University, New York, NY, USA)
- Luke F. O’Donnell (Grossman School of Medicine, New York University, New York, NY, USA)
- Yelena Chernyak (Langone Health, New York University, New York, NY, USA)
- Katie Tobin (Langone Health, New York University, New York, NY, USA)
- Robert J. Cerfolio (Grossman School of Medicine, New York University, New York, NY, USA)
- Fritz Francois (Grossman School of Medicine, New York University, New York, NY, USA)
- Leora I. Horwitz (Grossman School of Medicine, New York University, New York, NY, USA)
Synopsis:
- A study of 1,999 hospitalized COVID-19 patients in New York City, NY (1,251 male, 748 female). According to data from 2020¹, 17.25% of the population of the USA smoke tobacco (19.5% of males, 15.0% of females). Therefore, in this study, we expect to find a total of approximately 355 smokers (243 male, 112 female). However, only 104 of the patients were current smokers (5.2%). Thus, this study indicates that smokers in the USA are significantly less likely to be hospitalized due to COVID-19.
Relevant excerpt(s):
- “Surprisingly, though some have speculated that high rates of smoking in China explained some of the morbidity in those patients, we did not find smoking status to be associated with increased risk of hospitalization or critical illness. This is consistent with a handful of other studies that have previously shown a lack of association of smoking with pulmonary diseaseassociated ARDS (i.e. from pneumonia), as compared with non-pulmonary sepsis-associated ARDS.”
Related articles:
- Obesity is the biggest ‘chronic’ risk factor for coronavirus hospitalizations, largest US study of COVID-19 finds

8. The association of smoking status with SARS-CoV-2 infection, hospitalisation and mortality from COVID-19: A living rapid evidence review

https://www.qeios.com/read/UJR2AW.7
Published: 2020-04-23 (Most recent update: 2020-08-02)
Location of sample: China / US / Korea / UK
Sample size: 23,067
Authors:
- David Simons (Royal Veterinary College, RVC, London, United Kingdom)
- Lion Shahab (University College London, University of London, United Kingdom)
- Jamie Brown (University College London, University of London, United Kingdom)
- Olga Perski (University College London, University of London, United Kingdom)
Synopsis:
- A meta-analysis of 174 studies across 27 countries. Forty-five studies were conducted in China, 44 in the US, 18 in the UK, 11 in Mexico, nine in Spain, eight in France, six in Italy, six across multiple international sites, three in Brazil and Israel, two in Finland, Iran and Turkey and one from 15 further countries.
Relevant excerpt(s):
- “Conclusions: Across 174 studies, recorded smoking prevalence was generally lower than national prevalence estimates. Current smokers were at reduced risk of testing positive for SARS-CoV-2 and former smokers were at increased risk of hospitalisation, disease severity and mortality compared with never smokers.”

9. Characteristics and risk factors for COVID-19 diagnosis and adverse outcomes in Mexico: an analysis of 89,756 laboratory-confirmed COVID-19 cases

https://www.medrxiv.org/content/10.1101/2020.06.04.20122481v2
Published: 2020-06-04
Location of sample: Mexico
Sample size: 89,756
Authors:
- Theodoros Giannouchos (Pharmacotherapy Outcomes Research Center, University of Utah Health, USA)
- Roberto Sussman (Institute of Nuclear Sciences, National Autonomous University of Mexico, Mexico)
- Jose Manuel Mier (Institute of Minimally Invasive Thoracic Surgery, Angeles Lomas Hospital, Mexico)
- Konstantinos Poulas (Laboratory of Molecular Biology and Immunology, University of Patras, Greece)
- Konstantinos Farsalinos (Laboratory of Molecular Biology and Immunology, University of Patras, Greece)
Synopsis:
- A study of 89,756 laboratory–confirmed COVID-19 cases across Mexico (50,622 male, 39,134 female (+/- 1)). According to data from 2020¹, 13.7% of the population of Mexico smoke tobacco (20.8% of males, 6.6% of females). Therefore, in this study, we expect to find a total of approximately 13,111 smokers (10,529 male, 2,582 female). However, only 7,449 (+/- 1) of the patients were current smokers (8.3%). Thus, this study indicates that smokers in Mexico are significantly less likely to test positive for COVID-19. Whether this is due to smokers being less likely to contract SARS-CoV-2, or whether smokers are less likely to suffer severe enough symptoms to require testing/medical attention is unclear.
Relevant excerpt(s):
- Table 2 indicates the results of the two regressions on COVID-19 diagnosis for all patients in the data. Across both models, females and younger patients (0 to 17) were significantly less likely to be diagnosed with COVID-19 compared to males and to their 18 to 44 counterparts (p<0.001 for all). In addition, current smokers were approximately 23% less likely to be diagnosed with COVID-19 compared to non-smokers (p<0.001 in both models). In contrast, older patients (45 years of age or older) and those with one or more comorbidities were more likely to be diagnosed with COVID-19 compared to those aged 18 to 44 and those without comorbidities respectively. Diabetes and obesity were particularly associated with COVID-19 diagnosis compared to patients without such conditions (p<0.001 for all).

10. National Smoking Rates Correlate Inversely with COVID-19 Mortality

https://www.medrxiv.org/content/10.1101/2020.06.12.20129825v1
Published: 2020-06-12
Location of sample: Various (40 countries; the 20 hottest countries and the 20 coldest countries)
Sample size: Not specified
Authors:
- Michael J. Norden (University of Washington, Seattle, WA, USA)
- David H. Avery (University of Washington, Seattle, WA, USA)
- Justin G. Norden (Stanford University School of Medicine, Stanford, CA, USA)
- David R. Haynor (University of Washington, Seattle, WA, USA)
Synopsis:
- A meta-analysis of the association between smoking rates and COVID-19 mortality in the 20 hottest countries and the 20 coldest countries which found “a highly significant inverse correlation between current daily smoking prevalence and COVID-19 mortality rate”
Relevant excerpt(s):
- “Results: A highly significant inverse correlation between current daily smoking prevalence and COVID-19 mortality rate was noted for the group of hot countries (R=-.718, p = .0002), cold countries (R=-.567, p=.0046), and the combined group (R=-.324, p=.0207). However, after adjustments only the regression for hot countries and the combined group remained significant. In hot countries, for each percentage point increase in smoking rate mortality decreased by .147 per 100,000 population (95% CI .102- 192, p=.0066). This resulted in mortality rates several-fold elevated in the countries with the lowest smoking rates relative to the highest smoking rates. In the combined group, mortality decreased by .257 per 100,000 population (95% CI .175-.339, p=.0034).
  Discussion: These findings add support to the finding of an inverse relationship between current smoking and seriously symptomatic COVID-19. However, we conclude that the difference in mortality between the highest and lowest smoking countries appears too large to be due primarily to the effects of smoking per se. A potentially beneficial effect of smoking is surprising, but compatible with a number of hypothetical mechanisms which deserve exploration: 1) Studies show smoking alters ACE2 expression which may affect COVID-19 infection or its progression to serious lung pathology. 2) Nicotine has anti-inflammatory activity and also appears to alter ACE2 expression. 3) Nitric oxide in cigarette smoke is known to be effective in treating pulmonary hypertension and has shown in vitro antiviral effects including against SARS-CoV-2. 4) Smoking has complicated effects on the immune system involving both up and down regulation, any of which might alone or in concert antagonize progression of COVID-19. 5) Smokers are exposed to hot vapors which may stimulate immunity in the respiratory tract by various heat-related mechanisms (e.g. heat shock proteins). Studies of steam and sauna treatments have shown efficacy in other viral respiratory conditions. At this time there is no clear evidence that smoking is protective against COVID-19, so the established recommendations to avoid smoking should be emphasized. The interaction of smoking and COVID-19 will only be reliably determined by carefully designed prospective study, and there is reason to believe that there are unknown confounds that may be spuriously suggesting a protective effect of smoking. However, the magnitude of the apparent inverse association of COVID-19 and smoking and its myriad clinical implications suggest the importance of further investigation.”

11. Risk of severe COVID-19 disease with ACE inhibitors and angiotensin receptor blockers: cohort study including 8.3 million people

https://heart.bmj.com/content/early/2020/07/31/heartjnl-2020-317393
Published: 2020-07-31
Location of sample: UK
Sample size:8,275,949
Authors:
- Julia Hippisley-Cox (Primary Care Health Sciences, University of Oxford, Oxford, UK)
- Duncan Young (Adult Intensive Care Unit, John Radcliffe Hospital, Oxford, UK; Kadoorie Centre, University of Oxford, Oxford, UK)
- Carol Coupland (Division of Primary Care, School of Medicine, University of Nottingham, Nottingham, UK)
- Keith M. Channon (Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, John Radcliffe Hospital, University of Oxford, Oxford, UK)
- Pui San Tan (Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK)
- David A. Harrison (Clinical Trials Unit, ICNARC, London, UK)
- Kathryn Rowan (Intensive Care National Audit and Research Centre ICNARC, London, UK)
- Paul Aveyard (Nuffield Department of Primary Care Health Sciences, University of Oxford, Oxford, UK)
- Ian D. Pavord (Respiratory Medicine Unit and Oxford Respiratory NIHR BRC Nuffield Department of MedicineNDM Research BuildingOld Road CampusUniversity of Oxford, Oxford, UK)
- Peter J. Watkinson (Division of Cardiovascular Medicine, British Heart Foundation Centre of Research Excellence, John Radcliffe Hospital, University of Oxford, Oxford, UK; Nuffield Department of Clinical Neurosciences, Oxford NIHR BRC, University of Oxford, Oxford, UK)
Synopsis:
- A prospective cohort study using routinely collected data from 1,205 general practices in England with 8.28 million participants aged 20–99 years. Results indicate that smokers have a lower risk of ICU admission and of adverse outcomes from COVID-19 than nonsmokers, and the risk decrease was more pronounced among heavy and moderate smokers.
Relevant excerpt(s):
- “There was a small increased risk of both adverse outcomes among ex-smokers compared with never-smokers. We observed a markedly decreased risk of both COVID-19 disease and ICU admission in smokers. The apparent protective association was greatest for heavy and moderate smokers and most markedly on the risk of ICU admission which was 88% lower in heavy smokers compared with non-smokers.”
- “The counterintuitive finding of smokers having a lower risk of COVID-19 disease requiring hospital admission and ICU admission deserves further study.”

References