“The risk of infection by COVID-19 appears to be reduced by half among current smokers,” researchers have found.
A woman smokes a cigarette as she sits on a bench in Liverpool, following the outbreak of the coronavirus disease (COVID-19), Liverpool, Britain, May 26, 2020
(photo credit: PHIL NOBLE/REUTERS)
Smoking may offer some protection against the coronavirus, an Israeli study has found. The results support recent similar findings by researchers in France, China and Italy, although a British study has found the opposite.
Noting that conflicting reports exist regarding the impact of smoking on the likelihood of contracting the coronavirus, the Israeli team led by Dr. Ariel Israel undertook a population-based study pulling in data from over three million adult members of the Clalit Health Service, Israel’s largest healthcare provider.
Their results, presented in a non-peer reviewed paper published in medRxiv on Friday, found that “the risk of infection by COVID-19 appears to be reduced by half among current smokers.”
Of the more than three million adults included in the study, 114,545 had been tested for the virus, of whom just 4% tested positive. The researchers matched those who tested positive to those testing negative at a ratio of 1:4, taking into account as closely as possible variables such as age, sex and ethnicity. They found that among those who had tested positive, 9.8% were smokers against 19% of the overall population.
A previous smoking habit also appeared to confer some benefit, as 11.7% of those tested positive were former smokers against 13.9% in the general research population. Therefore, those who had previously smoked had a 19% lower risk of catching the virus, the results suggested.
These results appeared to hold even when previously existing conditions were taken into account – and of those who did test positive, there was no evidence that smoking worsened the symptoms of the disease.
“The magnitude of association observed for current smoking, with odds of infection reduced by about a half in smokers, suggests a genuine protective effect of smoking on the risk of COVID-19.”
The findings reflect comparable results in a recent study carried out by Prof. Zahir Amoura from Pitié Salpétrière Hospital in Paris, who found that, of 482 COVID-19 patients that presented to the hospital between February 28 and April 9, just 4.4% of in-patients and 5.3% of outpatients were daily smokers, against 25.4% of the general population.
That study also found that smokers were 80% less likely to develop severe symptoms, leading researchers to suggest that the nicotine in cigarettes binds to cell receptor sites, preventing the virus from taking hold by blocking access.
Similarly, University College, London, surveyed 28 papers and found the number of coronavirus victims who were smokers was “lower than expected”; a review of 13 Chinese studies found just 6.5% of 5,300 people hospitalized with corona were smokers; and a study by America’s Center for Disease control found that a mere 1.3% of more than 7,000 people who tested positive were smokers, against 14% of all Americans, according to The Daily Mail.
ON THE other hand, Dr. Nicholas Hopkinson’s team at Imperial College, London, assessed data from 2.4 million users of the COVID Sympto Study app, developed by Kings’s College London and Zoe.
On first use the app records key characteristics such as location, age, height, weight, smoking and common disease. Of the group, 11% were recorded as smokers, a little below the national average of 14%.
The study found that, of “standard users” – that is, someone who had not been tested for coronavirus – smokers were 14% more likely to experience three core symptoms of the disease: fever, a persistent cough and shortness of breath, The Daily Mail reported.
“Our results provide compelling evidence for an association between current smoking and individual risk from COVID-19, including symptom burden and risk of attending hospital,” the researchers wrote in their paper.
Despite this counter-evidence, some researchers are looking into nicotine as a potential therapeutic for COVID-19. They are giving nicotine patches to patients to see whether they reduce the instance and severity of coronavirus, particularly as the drug appeared to have beneficial effects in countering a phenomenon known as a cytokine storm, which occurs when the natural immune response goes into overdrive – an effect that can result in death.
“Nicotine has effects on the immune system that could be beneficial in reducing the intensity of the cytokine storm,” Dr. Konstantinos Farsalinos, from the University of West Attica, Greece, wrote in Internal and Emergency Medicine, according to The Daily Mail.
“The potential benefits of nicotine… could explain, at least in part, the increased severity or adverse outcome among smokers hospitalized for COVID-19, since these patients inevitably experience abrupt cessation of nicotine intake during hospitalization.
“This may be feasible through repurposing already approved pharmaceutical nicotine products such as nicotine patches.”