According to a new French study, smokers could be better protected than others from the novel coronavirus because nicotine blocks its docking sites. Another study, however, suggests exactly the opposite.
Smokers are generally considered a risk group for infections with the novel coronavirus. According to a study published in the Chinese Medical Journal, they usually contract more severe and protracted forms of the disease it causes, COVID-19, than non-smokers and die more often as a result.
However, French researchers led by Jean-Pierre Changeux, a neurobiologist at the Institut Pasteur, suspect that nicotine patches could help prevent infections with the dangerous virus. They have published a corresponding hypothesis on the science portal Qeios.
They came to this conclusion because their data, which contradicts that of the Chinese study, shows that there seems to be only a small number of smokers among COVID-19 patients.
The virus cannot enter the cell and cannot spread in the organism if nicotine blocks it, the researchers conclude.
The study looked at around 500 COVID-19 patients, of whom 350 had been treated in hospital and 150 had a mild disease progression. Only 5% were smokers, Zahir Amoura, head of the study and professor of internal medicine, told the news agency AFP. This in turn meant there were 80% fewer smokers among the COVID-19 patients than in the general population of the same age and gender cohort.
An earlier metastudy by researchers led by Giuseppe Lippi from Verona, Italy, published in the European Journal of Internal Medicine, came to a similar conclusion: that smokers are no more likely to contract COVID-19 than others.
Nicotine as protection?
The French study assumes that nicotine can protect against the new coronavirus. It is based on the hypothesis "that nicotine attaches to cell receptors (ACE2) used by the coronavirus, thereby preventing the virus from attaching," explains Changeux, who also holds a chair at the College de France.
The virus cannot enter the cell and cannot spread in the organism if nicotine blocks it, the researchers conclude. The Pitie-Salpetriere hospital in Paris is now to investigate this finding in more detail.
What role do ACE2 receptors really play?
However, there is no consensus among researchers that the ACE2 receptors have a blocking effect. Neurologists James L. Olds and Nadine Kabbani from Fairfax in the US state of Virginia had already published a study on the topic in The FEBS Journal on March 18.
This study suggests that nicotine, in fact, stimulates the cell receptors, meaning that viruses have even better opportunities to penetrate the cells. This could explain the particularly severe courses of the disease in smokers, the study says.
Smoking is not a solution
Only further research can show whether the French researchers or their US colleagues are right. Virtually all medical doctors, however, agree that tobacco smoking carries an additional risk in cases of COVID-19 disease.
They advise smokers to quit smoking as soon as possible, because the coronavirus primarily attacks the lungs, which are already damaged in smokers anyway.
Unlike when pure nicotine is assimilated — for example, through nicotine patches such as those used by people who want to quit smoking — smoking additionally burdens the body with many harmful substances, including carcinogenic agents.
Numerous studies and tests are still needed with nicotine patches of different dosages. If the French study proves to be correct, nicotine might even be able to protect people who come into contact with COVID-19 patients and are therefore at higher risk of infection.
However, taking nicotine is by no means harmless, because it is a toxic substance. When smoking a cigarette, the smoker absorbs about 1 to 3 milligrams of nicotine. One cigarette contains about 12 milligrams of nicotine.
More harm than good?
In the past, scientists had already looked at the possibility that nicotine might also have positive effects on the body. For example, researchers studied the effect of nicotine-like substances on the treatment of Parkinson's and Alzheimer's disease. For people with serious conditions like dementia, the benefits of nicotine were found to outweigh its disadvantages.
The results of the French study so far do not mean, however, that everyone should try to have a smoke as quickly and as often as possible.