Smokers are more likely to be admitted to hospital with Covid-19 and more likely to die from the disease, according to research published on Tuesday in the peer review journal Thorax.
The UK study pooled observational and genetic data on smoking, and contradicts research early in the pandemic that indicated smoking might offer protection against SARS-CoV-2, the coronavirus that causes Covid-19.
Smoking and its potential role in the coronavirus pandemic has been a deeply controversial issue in SA, after the government imposed a five-month ban on the sale of all tobacco in March 2020, just weeks after the first cases were detected in the country. It justified the ban with studies showing people who smoked were at greater risk of developing severe Covid-19, and said at the time that smoking increased the risk of transmission, particularly if people shared cigarettes. The ban was contested by tobacco companies, who said it boosted the trade in illicit cigarettes, jeopardised jobs, and led to a slump in tax revenue for the fiscus.
The study authors linked data from the UK Biobank, which contains genetic and health information from 500,000 participants, with primary care records, Covid-19 testing data, hospital admissions and death certificates between January and August 2020.
They found current smokers were 80% more likely to be admitted to hospital and significantly more likely to die from Covid-19 than people who had never smoked.
They also used a technique, known as Mendelian randomisation, to gauge whether a genetic predisposition to smoking and heavy smoking had a role in the severity of disease among more than 281,000 participants living in England. This analysis found a genetic predisposition to smoking was associated with a 45% higher risk of infection and a 60% higher risk of hospital admission for Covid-19. And it showed that a genetic predisposition to heavy smoking 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 dying Covid-19.
“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. So now might be as good a time as any to quit cigarettes and quit smoking,” said the study’s lead researcher Ashley Cliff, from Oxford University.
Waasila Jassat, a public health specialist from the National Institute for Communicable Diseases, said the study made an important contribution to scientists’ understanding of smoking and severe Covid-19 outcomes.
“The study is methodologically strong, uses large databases and reaches a congruent finding from two different analytical approaches, that point to the causal effect of smoking on the risk of severe Covid-19,” she said.
While there was increasing evidence of an association between smoking and poor Covid-19 outcomes, there was nevertheless some conflicting evidence, Jassat said. For example, research on Long Covid in SA found smoking was protective against persistent symptoms one month after Covid-19 hospitalisation. The Long Covid study has yet to be published.
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