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Evaluation of Smoking and Asymptomatic COVID-19 Disease in Health Professionals

Sağlık Çalışanlarında Sigara İçimi ve Asemptomatik COVID-19 Hastalığının Değerlendirilmesi

Melike Mercan Baspinar, Ezgi Tanimli, Gamze Keskin, Okcan Basat

Euras J Fam Med 2020;9(4):244-50. doi:10.33880/ejfm.2020090407


Original Research / Orijinal Araştırma


Aim: This study was conducted to assess smoking status and COVID-19 clinical severity in health professionals of a pandemic health center.

Methods: A retrospective study design based on data reports of a tertiary hospital between March 2020 and  June 2020 was realized. A comparison between the clinical disease severity and smoking status was analyzed by the SPSS 22.0 software statistic program at a significance level of p

Results: 150 participants (age 31.19±8.92 years; 48% female) were evaluated for the COVID disease clinical severity between the smokers (10.6%; 16/150) and non-smokers. The presence of asymptomatic (carriers) clinical disease (24%; 36/150) was found to be statistically significant in favor of smokers (8/16) versus non-smokers (28/134). Nicotine dependence level and Fagerstrom score had no clinical difference. Also, the occupation was significant for disease severity. Smokers among permanent workers with COVID versus doctors and nurses had a higher percentage in belong to the asymptomatic clinic (26/36) despite the higher rate of smoking (11/16).

Conclusion:  It was emphasized that higher rates of asymptomatic disease among smokers than that of symptomatic disease. Our study might contribute to epidemic control efforts that would help to explain the asymptomatic clinic and the different rates between smokers and non-smokers. 

Keywords: COVID-19, medical staff, nicotine dependence, smoking


Amaç: Bu çalışma, bir pandemi sağlık merkezinde çalışan sağlık profesyonellerinde sigara içme durumunu ve COVID-19 klinik şiddetini değerlendirmek için yapılmıştır.

Yöntem: Mart 2020 ile Haziran 2020 arasında üçüncü basamak bir hastanenin veri raporlarına dayanarak geriye dönük bir çalışma tasarımı gerçekleştirilmiştir. Klinik hastalık şiddeti ve sigara içme durumu arasındaki karşılaştırma SPSS 22.0 yazılım istatistik programı ile anlamlılık düzeyi p <0,05 olarak analiz edilmiştir.

Bulgular: Sigara içenler (%10,6; 16/150) ve sigara içmeyenler arasındaki COVID hastalığı klinik şiddeti açısından 150 katılımcı (31,19±8,92 yaş; %48 kadın) değerlendirildi. Asemptomatik (taşıyıcı) klinik hastalığa sahip olma olasılığı (%24; 36/150) sigara içenler (8/16) lehine olarak sigara içmeyenlerden (28/134)  istatistiksel olarak farklı bulundu. Nikotin bağımlılığı düzeyleri ve Fagerstrom skorları klinik açıdan  farklı değildi. Ayrıca meslek grubu hastalık şiddeti açısından anlamlı saptandı. Sigara içenler arasında daha fazla olmalarına (11/16) rağmen, COVID'li hizmetli statüsünde çalışan sürekli işcilerde doktor ve hemşirelere göre asemptomatik klinik görülme (26/36) yüzdesi daha yüksekti.

Sonuç: Sigara içenlerde asemptomatik hastalık oranlarının, semptomatik hastalığa göre daha yüksek olduğu vurgulanmıştır. Çalışmamız, asemptomatik kliniği ve sigara içenler ile içmeyenler arasındaki farklı oranları açıklamaya yardımcı olacak salgın kontrol çabalarına katkıda bulunabilir.

Anahtar kelimeler: COVID-19, sağlık çalışanları, nikotin bağımlılığı, sigara içme


Smoking has an increased risk for respiratory infection susceptibility and severity (1). Tobacco smoke exposure results in inflammatory processes in the lung such as increased mucosal inflammation, expression of inflammatory cytokines, impaired mucociliary clearance, etc. (2). Notably, COVID-19 is a disease of the respiratory tract characterized by severe acute respiratory syndrome (3). The Chinese Center for Disease Control and Prevention (CDC) has revealed the virus in January 2020. SARS-CoV-2 (Severe Acute Respiratory Syndrome Coronavirus 2) was announced by the World Health Organization (WHO) in January 2020 as an urgent public health problem and economic burden (4). In Turkey Coronavirus Science Board held its first meeting on 10 January 2020 and confirmed the first case was reported on March 10, 2020 (5). With the increase of COVID cases and pandemic mortality, speculations began to increase including whether smoking is a risk for COVID or not. 

In recent studies that assessed the clinical severity of COVID, high percentages of need for intensive care support or mechanical ventilation in current and former smokers have been drawn attention. Additionally, a higher percentage of smokers was shown among the severe cases who had died (6,7). It has been nearly estimated 80% of all infections remain undocumented because patients are asymptomatic or present with very mild symptoms (8). If asymptomatic patients are less likely to follow public health guidelines such as social distancing or self-isolation compared to patients who do exhibit symptoms, then providing information to asymptomatic patients that they are infected is a critical step in mitigating disease transmission (9). Despite many studies on severe disease classification, studies on a comparison for asymptomatic and symptomatic disease classification are not well-shown. 

We hypothesized that a difference between smokers and non-smokers is possible for the asymptomatic COVID infection (carriers) subtype versus symptomatic subtypes. The aims of this study were to determine the presence of smoking in health professionals with COVID infection, and to observe characteristics of symptomatic and asymptomatic patients based on nicotine dependence severity.


A retrospective data-based study was realized at Gaziosmanpaşa Training and Research Hospital which has been working as a pandemic hospital since the outbreak began in Istanbul city of Turkey. Health reports and data of the hospital between March 2020 and  June 2020 were searched after obtaining the permissions. Retrospective records of 150 health workers with laboratory or radiologically confirmed COVID-19 among verbally informed participants who accepted to reply the questions about their smoking status were included in the study. 

The initial score of the Fagerstrom Test for Nicotine Dependence (FTND) was used for the evaluation of nicotine dependence level by asking the FTND questions on a phone conversation, retrospectively. Reliability in the Turkish version of FTND and factor analysis was done in 2004 (10). Nicotine dependence was classified as mild (0-4 points), moderate (5-7 points), and heavy (8-10 points) dependence.

 In the United States, the National Institutes of Health (NIH) have categorized degrees of disease severity as follows (11) :  

  •    Asymptomatic or presymptomatic infection: Positive test for SARS-CoV-2 but no symptoms.
  •    Mild illness: Any signs and symptoms (eg, fever, cough, sore throat, malaise, headache, muscle pain) without shortness of breath, dyspnea, or abnormal chest imaging.
  •    Moderate illness: Evidence of lower respiratory disease by clinical assessment or imaging and a saturation of oxygen (SaO2) ≥94 percent on room air at sea level.
  •    Severe illness: Respiratory frequency >30 breaths per minute, SaO2 2/FiO2) <300, or lung infiltrates >50 percent.
  •    Critical illness: Respiratory failure, septic shock, and/or multiple organ dysfunction.

In our study, the clinical severity of COVID-19 infection has been classified in two groups as asymptomatic (presymptomatic) and symptomatic (including mild, moderate, severe, and critical severity) disease accompanied by multisystemic failure that can lead to a patient's death. The asymp-tomatic disease is defined as positive PCR test cases without any clinical symptoms and CT findings (5,8). 

The database was statistically analyzed using SPSS 22.0 software. Categorical data were compared using by Chi-square (X2) test. Continuous data were compared using by Mann-Whitney U test (non-normal distribution) or Student t-test (normal distribution) at a significant level of p <0.05.

Ethical approval was obtained from Taksim Training and Research Hospital Clinical Research Ethics Committee (02/06/2020 approval no:85) after online permission by the Turkish Ministry of Health (18/05/2020)  and Management of Gaziosmanpaşa Training and Research Hospital (15/05/2020) for collecting data.


The average age of 150 health professionals was 31.19 ± 8.92 years (min=20, max=65), 52% (n=78) were male and 48% (n=72) were female. The distribution of doctors, nurses, and permanent workers (including security personal, medical secretary, technical staff, cleaners, and others) was 13.3%, 44.7%, and 42%, respectively. The presence of current smoking was 10.6% (n=16). There were eleven smokers among permanent workers (69% of all smokers) and five smokers among nurses (31% of all smokers), although there was no current smoker among doctors. In smokers, the mean FTND score and all life cigarette consumption were 5.88 ± 2.33 points and 22.68 ± 10.41 cigarettes/per day. The mild, moderate, and heavy smoking percentages were 56.3%, 37.5%, 6.2%, respectively. The demographics and clinical characteristics of the study subjects are shown in Table 1. Additional diseases and chronic drug use among participants were not detected based on their health records in the hospital database.

24% of the participants (36/150) were in the asymptomatic (carrier, only PCR positive patients) patient group. The presence of asymptomatic clinical disease was found to be statistically significant in favor of smokers versus non-smokers (p=0.010). While the frequency of symptomatic disease among the smokers was 50% (8/16); it was 79% (106/134) for non-smokers. 1/20 (5%) of doctors, 9/67 (13.4%) of nurses, 26/63 (41.3%) of permanent workers were asymptomatic patients. The occupation was significant for disease severity (p <0.001). Smokers in permanent workers versus others had a higher percentage in belong to the asymptomatic clinic (26/36)  despite the higher rate of smoking (11/16).

In the evaluation of smoking, occupation, and disease severity, asymptomatic and symptomatic disease numbers were similar among current smokers but among non-smokers, symptomatic disease numbers had a higher rate than that of current smokers.


The primary outcome of our study was that asymptomatic COVID-19 cases (carriers) have seemed to relate to smokers more than non-smokers based on our study sample including health providers of a pandemic hospital. It was obtained one out of every four health professionals is an asymptomatic COVID carrier. This result was striking for the risk of person-to-person transmission with air spreading. In our country,  PCR (reverse-transcription polymerase chain reaction) tests have been performed according to the Turkish Ministry of Health’s COVID-19 diagnosis and treatment guidelines. According to the section for health workers in this guide, those who have no symptoms should be observed and tested when symptoms appeared or in contact with a COVID case ( However, there is no offer about the need for screening COVID tests for healthcare givers who have no symptoms.  Many cases that had no awareness of their disease were not tested depending on the absence of symptoms.

Asymptomatic infection is of particular importance as a source of disease in the community (12). The asymptomatic disease ratio was estimated to be 30.8% in a study searching viral testing for passengers on chartered evacuation flights from China to Japan (13). It has been estimated at 56–80% for influenza in another study (14). Perhaps less than half of COVID-19-infected individuals are asymptomatic (13). 

In a meta-analysis, the pooled prevalence of smoking in hospitalized people with COVID disease was found 7.63% (95% CI 3.83%-12.43%) (15). A cross-sectional study has shown that the daily smokers' rate was significantly lower in symptomatic COVID-19 patients than in the general population in France, for both outpatients and inpatients. The standardized incidence ratios for daily smokers in COVID-19 outpatients and inpatients had a decrease of 77% as compared to the French population, accounting for age and sex distribution (16). In our study, the presence of current smoking with COVID disease was 10.6% (16/150) and this rate was similar to a study that found the smoking rate as 11.1% (12/108) among SARS-CoV-2-positive health care providers. In the same study, the non-smoker rate was 17.9% among 327/1826 SARS-CoV-2-negative workers (17). 

According to studies among healthcare professionals, a relatively high presence of smoking is evident among doctors. The lowest overall smoking rate has been recorded in the US with 2% and the highest in Greece with 49%, following China (45%), and Japan (42%) (18). In Turkey, the smoking rate was 16% based on a study among physicians in Istanbul (19). In this present study, there was no smoker among doctors with COVID disease, despite 31% of nurses, 69% of permanent workers with COVID were smoking. At the same time, all doctors were symptomatic patients that means doctors were less asymptomatic (carrier). Especially, smokers among permanent workers versus others had a higher percentage of the asymptomatic clinic despite the higher rate of smoking. So, smokers in permanent workers had a higher disease spreading risk than that of doctors and nurses in the hospital. 

Several studies indicate that exposure to both active smoking and passive smoking increases the incidence of sneezing, sore throat, cough, and frequent cough (20). Since similar complaints are common symptoms of early COVID disease, complaints may be ignored and the virus may spread into the air by person‐to‐person transmission of carriers. So, smoking cessation treatments would be more important in the next pandemic days both health care providers and all smokers. Smoking should be considered a risk factor for the disease transmission until further availability of evidence and measures to limit its direct and indirect effects should be implemented within the community (21).

COVID-19 appears to eventually become a disease of the nicotinic cholinergic system. Nicotine could maintain or restore the function of the cholinergic anti-inflammatory system and thus control the release and activity of pro-inflammatory cytokines. This could prevent or suppress the cytokine storm damage to the lungs (22). It is now believed that there exists a cholinergic anti‐inflammatory pathway that acts through nicotinic acetylcholine receptors (23). So, known harms of chemicals within cigarette smoke, some studies have been suggested nicotine may be a therapeutic option. An investigation of the clinical effects of pharmaceutical nicotine must be searched on COVID-19 susceptibility, progression, and severity through clinical trials. This may be feasible through repurposing nicotine patches (i.e. as smoking substitutes) (24). Distinguishing medicinal nicotine treatment from cigarette smoking for the prevention and treatment of COVID-19 is critical: simply stated, smoking has no therapeutic role. In contrast, medicinal nicotine is a FDA approved, inexpensive, over the counter, readily available therapy with a longstanding safety record including low addiction potential, and few contraindications (25). Mounting epidemiologic evidence of lower SARS-CoV-2 infection rates among smokers may be explained by exposure to nicotine, as opposed to the thousands of harmful chemicals contained in cigarette smoke (25,26). In our study, a higher asymptomatic disease rate among smokers than that of non-smokers similarly was found. However, it would be an earlier decision to relate this result to the nicotine effect unless a large number of studies were done.

Limitations: First of all, one of the limitations of this search was that we could not well examine ex-smoking or intermittent smoking. We saw that people on the phone conversation tend to not talk about their nicotine addiction. So, former smokers may tend to hide real addiction levels for smoking stigma. The second limitation was that the information about nutrition, individual immunity level, depression, etc. did not exist. 


We found that smokers have a higher asymptomatic disease rate more than non-smokers. We thought that it might be related to the nicotine effect but we could not measure this effect clinically or in the laboratory results. Carriers among smokers are threatening to transmit the virus with the respiratory tract by cigarette smoke. Avoiding cigarette smoke would prevent viral spreading. It is imperative to ensure the safety of health-care workers. Regular COVID screening tests for health professionals before any symptoms or contact history and encouragement of smoking cessation should be considered. Our study might contribute to epidemic control efforts about the asymptomatic clinic and the different rates between smokers and non-smokers.


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How to cite / Atıf için: Mercan Baspinar M, Tanimli E, Keskin G, Basat O. Evaluation of smoking and asymptomatic COVID-19 disease in health professionals. Euras J Fam Med 2020;9(4):244-50. doi:10.33880/ejfm.2020090407.

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