Smoking is associated with worse outcomes of COVID-19 particularly among younger adults: a systematic review and meta-analysis

Abstract

Background Smoking impairs lung immune function and damages upper airways, increasing risks of contracting and severity of infectious diseases. This paper quantifies the association between smoking and COVID-19 disease progression. Methods We searched PubMed and Embase for studies published from January 1–May 25, 2020. We included studies reporting smoking behavior of COVID-19 patients and progression of disease, including death. We used random effects meta-analysis, meta-regression and locally weighted regression and smoothing to examine relationships in the data. Results We identified 46 peer-reviewed papers with a total of 22,939 COVID-19 patients, 5421 (23.6%) experienced disease progression and 2914 (12.7%) with a history of smoking (current and former smokers). Among those with a history of smoking, 33.5% experienced disease progression, compared with 21.9% of non-smokers. The meta-analysis confirmed an association between ever smoking and COVID-19 progression (OR 1.59, 95% CI 1.33–1.89, p = 0.001). Ever smoking was associated with increased risk of death from COVID-19 (OR 1.19, 95% CI 1.02–1.39, p = 0.003). We found no significant difference (p = 0.864) between the effects of ever smoking on COVID-19 disease progression between adjusted and unadjusted analyses, suggesting that smoking is an independent risk factor for COVID-19 disease progression. We also found the risk of having COVID-19 progression higher among younger adults (p = 0.001), with the effect most pronounced among younger adults under about 45 years old. Conclusions Smoking is an independent risk for having progression of COVID-19, including mortality. The effects seem to be higher among young people. Smoking prevention and cessation should remain a priority for the public, physicians, and public health professionals during the COVID-19 pandemic.

Risk Factors for Being Seronegative following SARS-CoV-2 Infection in a Large Cohort of Health Care Workers in Denmark

“…We did not have information about prior infection with other human coronaviruses, but because the severity of COVID-19 is associated with risk of being seronegative, it seems relevant to adjust results in future studies. In addition, smoking is associated with COVID-19 severity and progression ( 15 ), although we could not find a significant association between smoking status and being seronegative.…”

Effect modification by age of the association between obstructive lung diseases, smoking, and COVID-19 severity

“…[50][51][52] The observed inverse correlation between current smoking status and COVID-19 severity adds to the existing literature regarding the association between current smoking and risk of SARS-CoV-2 infection, disease severity and mortality. [53][54][55][56][57] Our findings contrast with observations from other common respiratory pathogens, including Middle East Respiratory Syndrome, in which smoking has been associated with increased risk of both infection and mortality, 58 59 influenza, in which history of smoking is associated with increased risk of hospital admission, 60 and respiratory syncytial virus, in which maternal smoking is associated with increased risk of acute lower respiratory infection in children. 61 Compared with former smokers and never smokers, current smoking is associated with an increased risk of death from pneumococcal pneumonia.…”

Smoking Behaviors, Mental Health, and Risk Perceptions during the Beginning of the COVID-19 Pandemic among Mexican Adult Smokers

“…Smoking is the leading cause of preventable death worldwide [10], and increases the risk for cancer, respiratory and cardiovascular diseases, inflammation, immunosuppression, diabetes mellitus, and diseases of nearly all organs in the body [11]. Many of these conditions exacerbate COVID-19, and studies have shown that smokers are at an increased risk for severe COVID-19 infection [12] and mortality [13]. It is also important to note that the COVID-19 pandemic has had a negative impact on mental health [14,15], increasing stress and diagnoses of anxiety and depression [16,17].…”

“…As smokers are at a higher risk of severe COVID-19 [12,13], and considering the relationship between smoking and mental health, there is a need to understand how smoking behaviors, symptoms of depression and stress, and risk perceptions among smokers have changed over the COVID-19 pandemic period, and how these outcomes relate with one another. Examining smoking frequency and quit attempts are important because they predict cessation [24][25][26].…”