A scientific paper claiming current smokers are 23% less likely to be diagnosed with Covid-19 compared to non-smokers has been retracted by a medical journal, after it was discovered some of the paper's authors had financial links to the tobacco industry.
But the paper, published in July last year by the European Respiratory Journal, found "current smoking was not associated with adverse outcome" in patients admitted to hospital with Covid, and claimed smokers were at a significantly lower risk of acquiring the virus, reports the Guardian.
The World Health Organization has warned that because smoking impairs lung function, there is an increased risk of severe symptoms if respiratory infections, including coronaviruses, are acquired by smokers.
The latest edition of the European Respiratory Journal included a retraction notice for the paper, stating: "It was brought to the editors' attention that two of the authors had failed to disclose potential conflicts of interest at the time of the manuscript's submission."
"That is, one of the authors (José M Mier) at the time had a current and ongoing role in providing consultancy to the tobacco industry on tobacco harm reduction; and another (Konstantinos Poulas) at the time was a principal investigator for the Greek NGO NOSMOKE - a science and innovation hub that has received funding from the Foundation for a Smoke Free World, an organisation funded by the tobacco industry," European Respiratory Journal said.
NOSMOKE, based in Greece, develops vaping products and promotes pro e-cigarette research from the tobacco industry.
In the paper, Mier, Poulas and their co-authors wrote "none" under "conflicts of interest".
The retraction notice said the authors did not agree with the decision. It said while failure to disclose a potential conflict of interest was not normally sufficient grounds for retraction, the editors felt the decision was justified based on the nature of the undisclosed relationship, and "in the context of the sensitive subject matter presented".
"The editors also acknowledge that at no point was there a question of any scientific misconduct on the part of any of the authors, aside from the failure of two contributing authors to disclose their conflicts of interest relating to the tobacco industry," the notice said.
The senior author of the paper, Konstantinos Farsalinos, said in a statement to the website Retraction Watch that the conflicts of interest "were irrelevant to the study's main aims and objectives".
"Additionally, I proposed to publicly release the full dataset and the statistical script so that all findings could be independently verified," he said.
"The editors declined. I requested my proposal to be mentioned in the retraction letter, but that was also rejected by the editors. I disagree with the retraction and I consider it unfair and unsubstantiated."
An analysis for the journal BMJ Evidence-Based Medicine "identified several biases and knowledge gaps which may give the false impression that smoking is protective in Covid-19".
The authors of that paper said there had been several studies that reported a so-called "smoker's paradox" with Covid-19, suggesting smokers might somehow be protected from infection and severe complications.
"As of now, the data supporting smoker's paradox claims are limited and questionable," the review found.
"In the context of smoking and Covid-19, poor data collection can lead to several erroneous conclusions. If patients with missing smoking data are not eliminated from the total pool, smokers may be wrongly underrepresented. Furthermore, it is difficult to get accurate history from patients who are either intubated or in respiratory failure," it added.
"If data from these patients are missing, and these patients are not removed from the denominator, it can give a false impression that smokers are less likely to develop severe disease. Second, it must be noted that most published studies have not reported the duration (years) or frequency (number of cigarettes) of smoking, hence these cannot be accounted for."