key: cord-355589-3zdv9zim
authors: Simons, David; Shahab, Lion; Brown, Jamie; Perski, Olga
title: The association of smoking status with SARS‐CoV‐2 infection, hospitalisation and mortality from COVID‐19: A living rapid evidence review with Bayesian meta‐analyses (version 7)
date: 2020-10-02
journal: Addiction
DOI: 10.1111/add.15276
sha: 
doc_id: 355589
cord_uid: 3zdv9zim

AIMS: To estimate the association of smoking status with rates of i) infection, ii) hospitalisation, iii) disease severity, and iv) mortality from SARS‐CoV‐2/COVID‐19 disease. DESIGN: Living rapid review of observational and experimental studies with random‐effects hierarchical Bayesian meta‐analyses. Published articles and pre‐prints were identified via MEDLINE and medRxiv. SETTING: Community or hospital. No restrictions on location. PARTICIPANTS: Adults who received a SARS‐CoV‐2 test or a COVID‐19 diagnosis. MEASUREMENTS: Outcomes were SARS‐CoV‐2 infection, hospitalisation, disease severity and mortality stratified by smoking status. Study quality was assessed (i.e. ‘good’, ‘fair’ and ‘poor’). FINDINGS: Version 7 (searches up to 25 August 2020) included 233 studies with 32 ‘good’ and ‘fair’ quality studies included in meta‐analyses. Fifty‐seven studies (24.5%) reported current, former and never smoking status. Recorded smoking prevalence among people with COVID‐19 was generally lower than national prevalence. Current compared with never smokers were at reduced risk of SARS‐CoV‐2 infection (RR=0.74, 95% Credible Interval (CrI) = 0.58‐0.93, τ = 0.41). Data for former smokers were inconclusive (RR=1.05, 95% CrI = 0.95‐1.17, τ = 0.17) but favoured there being no important association (21% probability of RR ≥1.1). Former compared with never smokers were at somewhat increased risk of hospitalisation (RR=1.20, CrI = 1.03‐1.44, τ = 0.17), greater disease severity (RR=1.52, CrI = 1.13‐2.07, τ = 0.29), and mortality (RR=1.39, 95% CrI = 1.09‐1.87, τ = 0.27). Data for current smokers were inconclusive (RR=1.06, CrI = 0.82‐1.35, τ = 0.27; RR=1.25, CrI = 0.85‐1.93, τ = 0.34; RR=1.22, 95% CrI = 0.78‐1.94, τ = 0.49 respectively) but favoured there being no important associations with hospitalisation and mortality (35% and 70% probability of RR ≥1.1, respectively) and a small but important association with disease severity (79% probability of RR ≥1.1). CONCLUSIONS: Compared with never smokers, current smokers appear to be at reduced risk of SARS‐CoV‐2 infection while former smokers appear to be at increased risk of hospitalisation, increased disease severity and mortality from COVID‐19. However, it is uncertain whether these associations are causal.

COVID-19 is a respiratory disease caused by the SARS-CoV-2 virus. Large age and gender differences in case severity and mortality have been observed in the ongoing COVID-19 pandemic 1 ; however, these differences are currently unexplained. SARS-CoV-2 enters epithelial cells through the angiotensin-converting enzyme 2 (ACE-2) receptor 2 . Some evidence suggests that gene expression and subsequent receptor levels are elevated in the airway and oral epithelium of current smokers 3,4 , thus putting smokers at higher risk of contracting SARS-CoV-2. Other studies, however, suggest that nicotine downregulates the ACE-2 receptor 5 . These uncertainties notwithstanding, both former and current smoking is known to increase the risk of respiratory viral 6,7 and bacterial 8, 9 infections and is associated with worse outcomes once infected. Cigarette smoke reduces the respiratory immune defence through peri-bronchiolar inflammation and fibrosis, impaired mucociliary clearance and disruption of the respiratory epithelium 10 . There is also reason to believe that behavioural factors (e.g. regular hand-to-mouth movements) involved in smoking may increase SARS-CoV-2 infection and transmission in current smokers. However, early data from the COVID-19 pandemic have not provided clear evidence for a negative impact of current or former smoking on SARS-CoV-2 infection or COVID-19 disease outcomes, such as hospitalisation or mortality 11 . It has also been hypothesised that nicotine might protect against a hyper-inflammatory response to SARS-CoV-2 infection, which may lead to adverse outcomes in patients with COVID-19 disease 12 .

There are several reviews that fall within the scope of smoking and COVID-19 11,13-18 . We aimed to produce a rapid synthesis of available evidence pertaining to the rates of infection, hospitalisation, disease severity and mortality from SARS-CoV-2/COVID-19 stratified by smoking status. Given the increasing availability of data on this topic, this is a living review with regular updates. As evidence accumulates, the review will be expanded to include studies reporting COVID-19 outcomes by alternative nicotine use (e.g., nicotine replacement therapy or e-cigarettes).

test to confirm prior infection, and 3.9% further studies relied on a combination of RT-PCR and clinical diagnosis (see Supplementary table S1) .

Categorisation of smoking status was heterogeneous (see Table 1 ). One-hundred-and-forty-five studies collected data on smoking status through routine electronic health records (EHRs), 59 studies used a bespoke case report form for COVID-19 and 29 studies did not state the source for information on smoking status. None of the studies verified smoking status biochemically. Notably, only 57 (24.4%) studies reported current, former and never smoking status (see Supplementary table   S2a) , with a further 17 studies reporting ever and never smoking status (see Supplementary table   S2b) . The remaining 159 studies reported current, current/former or current and former smoking status but did not explicitly state whether remaining participants were never smokers or if data were missing on smoking status (see Supplementary table S2c) . Seventy-eight studies explicitly reported the proportion with missing data on smoking status, which ranged from 0.08% to 96.4%.

Five studies recorded the use of alternative nicotine products in current and/or former smokers but did not report COVID-19 outcomes stratified by nicotine use [26] [27] [28] [29] [30] .

One study was performed in a random, representative population sample and was rated as 'good' quality. Forty-six studies were rated as 'fair' quality. The remaining 186 studies were rated as 'poor' quality (see Table 1 ).

Unadjusted smoking prevalence compared with overall estimates for national adult smoking prevalence split by country and study setting is presented in Figure 2a and 2b. Lower than expected current smoking prevalence was generally observed. Former smoking prevalence was more similar to expected prevalence when reported. National smoking prevalence estimates used for comparison are presented in Supplementary table 3.

Three studies provided data on access to SARS-CoV-2 diagnostic testing for those meeting local testing criteria by smoking status. In a cohort study of US military veterans aged 54-75 31 , current smokers were more likely to receive a test: 42.3% (1,603/3,789) of the sample were current smokers compared with 23.8% of all veterans aged 50+ years using any tobacco product between 2010-2015 32 . In the UK Biobank cohort 33 , former (RR = 1.29, 95% CI = 1.14-1. 45 , p < .001) and current (RR = 1.44, 95% CI = 1.20-1.71, p < .001) compared with never smokers were more likely to receive a test in a multivariable analysis. In an Australian rapid assessment screening clinic for COVID-19 34 , 9.4% (397/4,226) of the self-referred sample (subsequently assessed by a healthcare professional to decide on testing) were current smokers. Current compared with former or never smokers were less likely to require a test (RR = 0.93, 95% CI = 0.86-1.0, p = 0.045).

Forty-five studies provided data on SARS-CoV-2 infection for people meeting local testing criteria by smoking status (see Table 2 ). Meta-analyses were performed for one 'good' and 16 'fair' quality studies (see Figure 4 and 5). Current smokers were at reduced risk of testing positive for SARS-CoV-2 compared with never smokers (RR = 0.74, 95% CrI = 0.58-0.93, τ = 0.41, 95% CI = 0.24-0.64). The probability of current smokers being at reduced risk of infection compared with never smokers (RR ≤0.9) was 95%. Former compared with never smokers were at increased risk of testing positive, but data were inconclusive (RR = 1.05, 95% CrI = 0.95-1.17, τ = 0.17, 95% CI = 0.10-0.26) and favoured there being no important association. The probability of former smokers being at increased risk of infection (RR ≥1.1) compared with never smokers was 21%. Results were materially unchanged in the two sensitivity analyses (see Supplementary figure S2).

Twenty-nine studies examined hospitalisation for COVID-19 disease stratified by smoking status (see Table 3 ). Meta-analyses were performed for eight 'fair' quality studies (see Figure 6 and 7). Current (RR = 1.06, CrI = 0.82-1.35, τ = 0.27, 95% CI = 0.08-0.55) and former (RR = 1.20, CrI = 1.03-1.44, τ = 0.17, 95% CI = 0.06-0.37) compared with never smokers were at increased risk of hospitalisation with COVID-19, but data for current smokers were inconclusive and favoured there being no important association. The probability of current and former smokers being at increased risk of hospitalisation compared with never smokers was 35% and 89%, respectively. Results were materially unchanged in two sensitivity analyses (see Supplementary figure S3).

Sixty studies reported disease severity in hospitalised patients stratified by smoking status (see Table   4 ). Severe (as opposed to non-severe) disease was broadly defined as requiring intensive treatment unit (ITU) admission, requiring oxygen as a hospital inpatient or in-hospital death. Meta-analyses were performed for eight 'fair' quality studies (see Figure 8 and 9). Current (RR = 1.25, CrI = 0.85-1.93, τ = 0.34, 95% CI = 0.01-0.86) and former (RR = 1.52, CrI = 1.13-2.07, τ = 0.29, 95% CI = 0.47-0.66) compared with never smokers were at increased risk of greater disease severity; data for current smokers were inconclusive but favoured there being a small but important association. The probability of current and former smokers having increased risk of greater disease severity compared with never smokers was 79% and 98%, respectively. Results were materially unchanged in two sensitivity analyses (see Supplementary figure S4 ).

Fifty studies reported mortality from COVID-19 by smoking status (see Table 5 ), with nine 'fair' quality studies included in meta-analyses (see Figure 10 and 11). Current (RR = 1.22, 95% CrI = 0.78-1.94, τ = 0.49, 95% CI = 0.16-0.99) and former (RR = 1.39, 95% CrI = 1.09-1.87, τ = 0.27, 95% CI = 0.05-0.58) compared with never smokers were at increased risk of in-hospital mortality from COVID-19.

Data for current smokers were inconclusive but favoured there being no important association. The probability of current and former smokers being at greater risk of in-hospital mortality compared with never smokers was 70% and 97%, respectively. Results were materially unchanged in two sensitivity analyses (see Supplementary figure S5 ).

This living rapid review found uncertainty in the majority of 233 studies arising from the recording of smoking status. Notwithstanding these uncertainties, compared with overall adult national prevalence estimates, recorded current smoking rates in most countries were lower than expected.

In a subset of better of quality studies (n = 17), current smokers had a reduced risk of testing positive for SARS-CoV-2 but appeared more likely to present for testing and/or receive a test. Data for current smokers on the risk of hospitalisation, disease severity and mortality were inconclusive, but favoured there being no important associations with hospitalisation and mortality and a small but important increase in the risk of severe disease. Former smokers were at increased risk of hospitalisation, disease severity and mortality compared with never smokers.

Interpretation of results from studies conducted during the first phase of the SARS-CoV-2 pandemic is complicated by several factors (see Figure 12 ): 1) Exposure to SARS-CoV-2 is heterogeneous with different subgroups at heightened risk of infection at different stages of the pandemic. This will likely introduce bias in studies assessing the rate of infection by smoking status conducted early on.

2) Current and former smokers may be more likely to meet local criteria for community testing due to increased prevalence of symptoms consistent with SARS-CoV-2 infection, such as cough, increased sputum production or altered sense of smell or taste 35 . Evidence from a small number of studies indicates that current smokers may be more likely to present for testing, hence increasing the denominator in comparisons with never smokers and potentially inflating the rate of negative tests in current smokers. Infection positivity rates estimated among random samples will be more informative than currently available data. We identified one population study conducted in Hungary reporting on seroprevalence and smoking status 36 ; however, the response rate was fairly low at 58.8% and the current smoking rate was 10 percentage points below national prevalence estimates, thus questioning the representativeness of the final sample. Smoking status is being collected in at least two large representative infection and antibody surveys in the UK 37,38 .

3) Testing for acute infection requires swabbing of the mucosal epithelium, which may be disrupted in current smokers, potentially altering the sensitivity of assays 39 . 4) Diagnostic criteria for SARS-CoV-2 infection and COVID-19 have changed during the course of the pandemic 40 . It was not possible to extract details on the specific RT-PCR technique or platforms used across the included studies due to reporting gaps. Different platforms have varying sensitivity and specificity to detect SARS-CoV-2 infection. 5) Most included studies relied on EHRs as the source of information on smoking status.

Research shows large discrepancies between EHRs and actual behaviour 41 . Known failings of EHRs include implausible longitudinal changes, such as former smokers being recorded as never smokers at subsequent hospital visits 41 . Misreporting on the part of the patient (perhaps due to perceived stigmatisation) has also been observed, with biochemical measures showing higher rates of smoking compared with self-report in hospitalised patients in the US 42 . It is hence possible that underreporting of current and former smoking status in hospitals occurred across the included studies. 6) Individuals with severe COVID-19 symptoms may have stopped smoking immediately before admission to hospital and may therefore not have been recorded as current smokers (i.e. reverse causality).

Smokers with COVID-19 may be less likely to receive a SARS-CoV-2 test or present to hospital due to lack of access to healthcare and may be more likely to die in the community from sudden complications (i.e. self-selection bias) and thus not be recorded. 8) If there is a protective effect of nicotine on COVID-19 disease outcomes, abrupt nicotine withdrawal upon hospitalisation may lead to worse outcomes 12 . 9) During periods of heightened demand of limited healthcare resources, current and former smokers with extensive comorbidities may have reduced priority for intensive care admission, thus leading to higher in-hospital mortality.

10) Given lack of knowledge of the disease progression and long-term outcomes of COVID-19, it is unclear whether studies conducted thus far in the pandemic have monitored patients for a sufficient time period to report complete survival outcomes or whether they are subject to early censoring. 11) Reasons for hospitalisation vary by country and time in the pandemic. For example, early cases may have been hospitalised for isolation and quarantine reasons and not due to medical necessity. It is plausible this may have skewed early data towards less severe cases. In addition, the observed association between former smoking and greater disease severity may be explained by collider bias 43 , where conditioning on a collider (e.g. testing or hospitalisation) by design or analysis may introduce a spurious association between current or former smoking (a potential cause of testing or hospitalisation) and SARS-CoV-2 infection/adverse outcomes from COVID-19 (potentially exacerbated by smoking) 44 .

This living rapid evidence review was limited by having a single reviewer extracting data with a second independently verifying the data extracted to minimise errors, restricting the search to one electronic database and one pre-print server and by not including at least three large population surveys due to their reliance on self-reported suspected or confirmed SARS-CoV-2 infection (which means they do not meet our eligibility criteria) 35, 45, 46 . We also did not include a large, UK-based, representative seroprevalence study 47 in our meta-analyses as the odds of testing positive in former smokers was not reported. However, the odds of infection for current smokers (OR = 0.64, 95% CI = 0.58-0.71) was in concordance with the pooled estimate in our meta-analysis. Population surveysparticularly with linked data on confirmed infection or antibodies -will be included in future review versions to help mitigate some of the limitations of healthcare based observational studies. The comparisons of current and former smoking prevalence in the included studies with national prevalence estimates did not adjust observed prevalence for the demographic profile of those tested/admitted to hospital. Other reviews focused on this comparison have applied adjustments for sex and age, and continue to find lower than expected prevalence -notwithstanding the issues complicating interpretation described above 17 .

Further scientific research is needed to resolve the mixed findings summarised in our review. Such trials should focus on medicinal nicotine (as smoked tobacco is a dirty delivery mechanism that could mask beneficial effects) and potentially differentiate between different modes of delivery (i.e. inhaled vs. ingested) since this can affect pharmacokinetics 48 and potential therapeutic effects. A second research priority would be a large, representative (randomly sampled) population survey with a validated assessment of smoking status which distinguishes between recent and long-term ex-smokers -ideally biochemically verified -and assesses seroprevalence and links to health records.

In the meantime, public-facing messages about the possible protective effect of smoking or nicotine are premature. In our view, until there is further research, the quality of the evidence does not justify the huge risk associated with a message likely to reach millions of people that a lethal activity, such as smoking, may protect against COVID-19. It continues to be appropriate to recommend smoking cessation and emphasise the role of alternative nicotine products to support smokers to stop as part of public health efforts during COVID-19. At the very least, smoking cessation reduces acute risks from cardiovascular disease and could reduce demands on the healthcare system 49 . GPs and other healthcare providers can play a crucial role -brief, high-quality and free online training is available at National Centre for Smoking Cessation and Training.

Across 234 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. Analysis. medRxiv 2020. DOI This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Note. -Age not provided for total sample; ^ Denotes mean (SD). * This study was rated as 'poor' quality as the manuscript only presents data for current (but not former) smokers despite having obtained complete smoking status, thus resulting in >20% missing data on smoking status. This article is protected by copyright. All rights reserved.

Note. Niedzwiedz et al. reported on SARS-CoV-2 infection by smoking status in multivariable analyses but did not present raw data. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Note. Solis et al. and the OpenSAFELY Collaborative reported on mortality by smoking status in a multivariable analysis but did not present raw data for both the exposure and outcome variables. 

Status in Electronic Health Records

Prevalence of smoking assessed biochemically in an urban public hospital: a rationale for routine cotinine screening

Collider bias undermines our understanding of COVID-19 disease risk and severity

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Geo-social gradients in predicted COVID-19 prevalence and severity in Great Britain : results from Affiliations : Corresponding authors : Understanding the geographical distribution of COVID-19 through the general population is key to the provision of ade

COVID-19, smoking, and inequalities: a cross-sectional survey of adults in the UK

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Analysis of Epidemiological and Clinical Features in Older Patients With Coronavirus Disease 2019 (COVID-19) Outside Wuhan

Epidemiological, clinical and virological characteristics of 74 cases of coronavirus-infected disease 2019 (COVID-19) with gastrointestinal symptoms

Clinical characteristics of 113 deceased patients with coronavirus disease 2019: retrospective study

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Analysis of factors associated with disease outcomes in hospitalized patients with 2019 novel coronavirus disease

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Host susceptibility to severe COVID-19 and establishment of a host risk score: findings of 487 cases outside Wuhan

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

Characterization and clinical course of 1000 patients with coronavirus disease 2019 in New York: retrospective case series

COVID-19 Fatality and Comorbidity Risk Factors among Confirmed Patients in Mexico

Presenting Characteristics, Comorbidities, and Outcomes Among 5700 Patients Hospitalized With COVID-19 in the New York City Area

Cluster of COVID-19 in northern France: A retrospective closed cohort study

Letter to the Editor: Obesity as a risk factor for greater severity of COVID-19 in patients with metabolic associated fatty liver disease

Clinical Characteristics and Risk factors for developed COVID-19 patients transferring to designated hospital from Jianghan Fangcang shelter Hospital: a retrospective, observational study

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Clinical characteristics of imported and second-generation COVID-19 cases outside Wuhan, China: A multicenter retrospective study

Impaired type I interferon activity and exacerbated inflammatory responses in severe Covid-19 patients

Characteristics and Clinical Outcomes of Adult Patients Hospitalized with COVID-19 -Georgia

Association Between Clinical Manifestations and Prognosis in Patients with COVID-19

Epidemiological and clinical characteristics analysis of COVID-19 in the surrounding areas of Wuhan, Hubei Province in 2020

Low albumin levels are associated with poorer outcomes in a case series of COVID-19 patients in Spain: a retrospective cohort study

Clinical characteristics of 106 patients with neurological diseases and co-morbid coronavirus disease 2019: a retrospective study

Neutrophil calprotectin identifies severe pulmonary disease in COVID-19

Smoking and the risk of COVID-19 infection in the UK Biobank Prospective Study

Multivariable prediction model of intensive care unit transfer and death: a French prospective cohort study of COVID-19 patients

Determinants of Severity in Cancer Patients with COVID-19 Illness

OpenSAFELY: factors associated with COVID-19 death in 17 million patients

A Cohort of Patients with COVID-19 in a Major Teaching Hospital in Europe

30-day mortality in patients hospitalized with COVID-19 during the first wave of the Italian epidemic: A prospective cohort study

Clinical features, diagnostics, and outcomes of patients presenting with acute respiratory illness: a comparison of patients with and without COVID-19

Clinical and Genetic Characteristics of Covid-19 Patients from UK Biobank

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Cardiac Structural and Functional Characteristics in Patients with Coronavirus Disease

COVID-19 outcomes in MS: Observational study of early experience from NYU Multiple Sclerosis Comprehensive Care Center

Early experience with COVID-19 patients at academic hospital in Southwestern United States

A Risk Score to Predict Admission to Intensive Care Unit in Patients With COVID-19: The ABC-GOALS Score

Dynamic liver function indexes monitoring and clinical characteristics in three types of COVID-19 patients

Derivation and validation of a prognostic model for predicting in-hospital mortality in patients admitted with COVID-19 in Wuhan, China: the PLANS (Platelet Lymphocyte Age Neutrophil Sex) model

Severe obesity, increasing age and male sex are independently associated with worse in-hospital outcomes, and higher in-hospital mortality

Hydroxychloroquine and Tocilizumab Therapy in COVID-19 Patients -An Observational Study

COVID-19: the key role of pulmonary capillary leakage. An observational cohort study

Clinical characteristics of 101 COVID-19 nonsurvivors in Wuhan, China: a retrospective study

COVID-19 in London, a Case Series Demonstrating Late Improvement in Survivors

Characteristics and outcome of SARS-CoV-2 infection in cancer patients

Risk factors for hospital admission related to COVID-19 in inflammatory rheumatic diseases

Silent Disease and Loss of Taste and Smell are Common Manifestations of SARS-COV-2 Infection in a Quarantine Facility: First report from Saudi Arabia

Risk of infection and hospitalization by Covid-19 in Mexico: a case-control study

Characteristics associated with hospitalisation for COVID-19 in people with rheumatic disease: data from the COVID-19

Global Rheumatology Alliance physician-reported registry

Olfactory Dysfunction in Recovered Coronavirus Disease 2019 (COVID-19) Patients

Psychosocial factors and hospitalisations for COVID-19: Prospective cohort study of the general population

Clinical predictors of donor antibody titer and correlation with recipient antibody response in a COVID-19 convalescent plasma clinical trial

Chronic ACE Inhibitor use is Associated with Decreased Odds of Severe Disease in Patients with COVID-19

Intraluminal Carotid Artery Thrombus in COVID-19: Another Danger of Cytokine Storm?

Impact of SARS-CoV-2 Viral Load on Risk of Intubation and Mortality Among Hospitalized Patients with Coronavirus Disease

IL6 inhibition in critically ill COVID-19 patients is associated with increased secondary infections

Profiling pre-symptomatic and asymptomatic cases with confirmed SARS-CoV-2 infection in Mexico City

Association of SARS-CoV-2 Genomic Load with COVID-19 Patient Outcomes

Health-care workers with COVID-19 living in Mexico City: clinical characterization and related outcomes

ROX Index Predicts Intubation in Patients with COVID-19 Pneumonia and Moderate to Severe Hypoxemic Respiratory Failure Receiving High Flow Nasal Therapy

Low plasma 25(OH) vitamin D3 level is associated with increased risk of COVID-19 infection: an Israeli population-based study

Pre-diagnostic circulating concentrations of insulin-like growth factor-1 and risk of COVID-19 mortality: results from UK Biobank

Association of Cancer with Risk and Mortality of COVID-19: Results from the UK Biobank

Natural killer cell activation related to clinical outcome of COVID-19

Digestive Manifestations in Patients Hospitalized with COVID-19

Risk Factors Prediction, Clinical Outcomes, and Mortality of COVID-19 Patients

Early Diagnosis and Clinical Significance of Acute Cardiac Injury -Under the Iceberg: A Retrospective Cohort Study of 619 Non-critically Ill Hospitalized COVID-19 Pneumonia Patients

Clinical outcomes and risk factors for severe COVID-19 infection in patients with haematological disorders receiving chemo-or immunotherapy

Initial experience in Mexico with convalescent plasma in COVID-19 patients with severe respiratory failure, a retrospective case series

Observational Study of Haloperidol in Hospitalized Patients with Covid-19

COVID-19 Case Series at UnityPoint Health St. Lukes Hospital in Cedar Rapids

Broncho-alveolar inflammation in COVID-19 patients: a correlation with clinical outcome

IgG antibody seroconversion and the clinical progression of COVID-19 pneumonia: A retrospective, cohort study | medRxiv

Early Improvement of Acute Respiratory Distress Syndrome in Patients with COVID-19: Insights from the Data of ICU Patients in Chongqing

The First Consecutive 5000 Patients with Coronavirus Disease 2019 from Qatar; a Nation-wide Cohort Study

Higher Comorbidities and Early Death is Characteristic of Hospitalized African-American Patients with COVID-19

Neutrophil calprotectin identifies severe pulmonary disease in COVID-19

Association between SSRI Antidepressant Use and Reduced Risk of Intubation or Death in Hospitalized Patients with Coronavirus Disease 2019: a Multicenter Retrospective Observational Study

Risk Factors for Hospitalization and Mortality due to COVID-19 in Espírito Santo State

Association of olfactory dysfunction with hospitalization for COVID-19: a multicenter study in Kurdistan

The Outcome of COVID-19 Patients with Acute Myocardial Infarction

Patient characteristics and predictors of mortality in 470 adults admitted to a district general hospital in England with Covid-19

Covid-19 serology in nephrology health care workers

Clinical Outcomes With the Use of Prophylactic Versus Therapeutic Anticoagulation in COVID-19

Comparative Incidence and Outcomes of COVID-19 in Kidney or Kidney-Pancreas Transplant Recipients Versus Kidney or Kidney-Pancreas Waitlisted Patients: A Pilot Study

Renin-Angiotensin-Aldosterone-System inhibitor use in patients with COVID-19 infection and prevention of serious events: a cohort study in commercially insured patients in the US

Colombian COVID19 First Experience in Gastroentrology. Characterization of digestive manifestations in patients diagnosed with COVID-19 at a highly complex institution in Bogota D.C., Colombia

The impact of COVID-19 on patients with asthma

Observational Study of the Efficiency of Treatments in Patients Hospitalized with Covid-19 in Madrid

Epidemiological and clinical features of 2019-nCoV acute respiratory disease cases in Chongqing municipality, China: a retrospective, descriptive, multiple-center study

Outcomes of Persons With COVID-19 in Hospitals With and Without Standard Treatment With (Hydroxy)chloroquine

Clinical characteristics of COVID-19 and the model for predicting the occurrence of critically ill patients: a retrospective cohort study

First report of tocilizumab use in a cohort of Latin American patients hospitalized for severe COVID-19 pneumonia

Obesity and Smoking as Risk Factors for Invasive Mechanical Ventilation in COVID-19: a Retrospective

Obesity, old age and frailty are the true risk factors for COVID-19 mortality and not chronic disease or ethnicity in Croydon

Post-discharge health status and symptoms in patients with severe COVID-19

Comparative Clinical Outcomes and Mortality in Prisoner and Non-Prisoner Populations Hospitalized with COVID-19: A Cohort from Michigan

Severe COVID-19 and Diabetes: A Retrospective Cohort Study from Three London Teaching Hospitals

Descriptive epidemiology of 16,780 hospitalized COVID-19 patients in the United States. medRxiv 2020; : 2020.07.17.20156265. and Severity of COVID-19 Disease in Patients from Boston Area Hospitals

Clinical manifestations of patients with Coronavirus Disease 2019 (COVID-19) attending at hospitals in Bangladesh

Sex-specificity of mortality risk factors among hospitalized COVID-19 patients in New York City: prospective cohort study

Early Clinical Factors Predicting the Development of Critical Disease in Japanese Patients with COVID-19: A Single-Center Retrospective

Eleven Routine Clinical Features Predict COVID-19 Severity

Understanding the patterns of repeated testing for COVID-19: Association with patient characteristics and outcomes

A Retrospective Study on Efficacy and Safety of Guduchi Ghan Vati for Covid-19 Asymptomatic Patients

Liver Enzyme Elevation in Coronavirus Disease 2019: A Multicenter, Retrospective, Cross-Sectional Study

Risk of COVID-19 in health-care workers in Denmark: an observational cohort study

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

Prevalence and outcome of Covid-19 infection in cancer patients: a national VA study

Positive Acute Coronary Syndrome Patients; a multisource Electronic Healthcare Records Study from England

An original short review for the Royal College of Physicians was converted to an extended living 

All data contributing to the current and future review versions are available here: https://doi.org/10.6084/m9.figshare.12756020All code required to reproduce the current and future analyses are available here: https://doi.org/10.5281/zenodo.4002046

This article is protected by copyright. All rights reserved.