Smokers are 60% to 80% more likely to be admitted to hospital with Covid-19 and also more likely to die from the disease, the data suggests.
A study, which pooled observational and genetic data on smoking and Covid-19 to strengthen the evidence base, contradicts research published early in the pandemic suggesting that smoking may help protect against the virus. This was later removed after it was discovered that some of the article’s authors had financial ties to the tobacco industry.
Other studies to determine whether smoking is associated with a greater likelihood of more serious Covid-19 infection have produced inconsistent results.
One problem is that most of these studies have been observational, making it difficult to establish whether smoking is the cause of an increased risk, or if something else is to blame, as smokers are more likely to. come from a lower socio-economic background.
Oxford University’s Dr Ashley Clift and colleagues relied on GP health records, Covid-19 test results, hospital admission data and death certificates to identify associations between smoking and the severity of Covid-19 from January to August 2020 in 421,469 participants in the UK Biobank study – all of whom had also already had their genetic makeup analyzed.
Compared to those who had never smoked, current smokers were 80% more likely to be admitted to hospital and significantly more likely to die from Covid-19 if infected.
To investigate, Clift and her team used a technique called Mendelian randomization, which uses genetic variants as a proxy for a particular risk factor – in this case, genetic variants that help determine whether a person is more likely to smoke or to smoke a lot – for further evidence. for a causal relationship.
While the contribution of each of these variants is small, and it is not necessarily understood why they increase a person’s chances of being a smoker, they avoid many of the limitations of observational studies and thus help give a clearer picture of the existence of a biological link between smoking and Covid-19.
“The study strengthens our confidence that smoking does not protect against Covid-19, as their Mendelian randomization analyzes are less likely to be confused than previous observational studies,” wrote Dr Anthony Laverty and the professor. Christopher Millett of Imperial College London in a linked editorial published in the journal Thorax.
Mendelian randomization analysis also confirmed the link between smoking and worse Covid-19 outcomes, concluding that a genetic predisposition to smoking was associated with a 45% higher risk of infection and a 60% higher risk. high hospitalization rate for Covid-19.
A genetic predisposition to smoking has been associated with a more than doubled risk of infection; a fivefold increase in the risk of hospitalization; and a tenfold increase in the risk of death from the virus, the team found.
Clift said: “Our results strongly suggest that smoking is linked to your risk of getting severe Covid, and just like smoking affects your risk for heart disease, different cancers and all of those other conditions that we know as smoking is related, it seems to be the same for the covid. So now might be a good time to quit smoking and quit smoking. “