London, Sep 28 Smoking is highly likely to worsen the severity of Covid-19 and the risk of dying from the infection, finds a large study.
Several studies carried out early on in the pandemic reported a lower prevalence of active smokers among people admitted to hospital with Covid-19 than in the general population, baffling scientists.
But in the new study, researchers at University of Oxford pooled both observational and genetic data, to show that smokers were 80 per cent more likely to be admitted to hospital and significantly more likely to die from Covid-19.
The results, published online in the respiratory journal Thorax, revealed that a genetic predisposition to smoking was associated with a 45 per cent higher risk of infection and a 60 per cent higher risk of hospital admission for Covid-19.
And it showed that a genetic predisposition to smoke more heavily was associated with a more than doubling in the risk of infection; a five-fold increase in the risk of hospital admission; and a 10-fold increase in the risk of death from the virus.
"Our results strongly suggest that smoking is related to your risk of getting severe Covid, and just as smoking affects your risk of heart disease, different cancers, and all those other conditions we know smoking is linked to, it appears that it's the same for Covid," lead researcher Ashley Clift, from the varsity's Nuffield Department of Primary Care Health Sciences.
"So now might be as good a time as any to quit cigarettes and quit smoking has a clear message for smokers," he added.
For the study, the team analysed the Covid-19 test results, hospital admissions data and death certificates of more than 420,000 patients.
Among nearly 14,000 smokers, there were 51 Covid admissions equivalent to one in 270 being hospitalised.
There were also up to 36 deaths equating to one in 384 succumbing to the virus.
On the other hand, among the 250,000 non-smokers there were 440 hospitalisations equivalent to one in almost 600. The team added there were a further 159 Covid deaths equivalent to one in 1,666, the Daily Mail reported.
"The idea that tobacco smoking may protect against Covid-19 was always an improbable one," said Drs Anthony Laverty and Christopher Millet of Imperial College London, in a linked editorial.
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