A new study has busted the myth that smoking can help protect you against COVID-19 - in fact, it makes you much more likely to catch the disease and end up in hospital.
Early in the pandemic, a paper was published which claimed only a fraction - about 5 percent - of those hospitalised in France with the disease were smokers, which made up 25 percent of the adult population.
The conclusion was that somehow smoking was preventative against contracting the virus and falling seriously ill. Suggested mechanisms were nicotine's anti-inflammatory properties, or that it latches onto the same ACE3 cell receptor used by the SARS-CoV-2 virus (which causes COVID-19), blocking it from getting into the smoker's cells.
The finding made headlines, but less well-publicised was that earlier this year the paper was retracted - it turned out two of its main authors had financial links to the tobacco industry.
Smokers typically fare worse at fighting respiratory diseases like COVID-19 than non-smokers, so to settle the "smoker's paradox" researchers at the University of Oxford looked at data from nearly half a million people in the UK's Biobank study.
Everyone in this long-term study has had their genetic makeup analysed, allowing scientists to look at whether people with a genetic predisposition towards smoking have better or worse outcomes than others, as well as those on the record as actual smokers.
They found compared with those who had never smoked, current smokers were 80 percent more likely to end up in hospital and significantly more likely to die from COVID-19. Those with a genetic predisposition towards smoking were 45 percent more likely to be infected and 60 percent more likely to be hospitalised.
For those whose genetics suggested a good chance they'd be heavy smokers, they were five times more likely to be hospitalised and 10 times more likely to die.
The process of using genetic markers as a proxy for data that might otherwise be hard to collect is called Mendelian randomisation. Prof Michael Baker of the University of Otago, one of New Zealand's best-known faces in the fight against COVID-19, told Newshub in June Mendelian randomisation was a good way to get around confounding factors that can make it difficult to link causes to effects. In that case, it was used to debunk previous claims high doses of vitamin D could prevent COVID-19.
"The idea that tobacco smoking may protect against COVID-19 was always an improbable one," the authors of the latest study, published in the journal Thorax, said.
"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," said lead researcher Ashley Clift.
"Now might be as good a time as any to quit cigarettes and quit smoking."
