SAN FRANCISCO - Researchers at UCSF published a study Tuesday indicating people with a history of smoking have nearly double the risk of having severe COVID-19 outcomes if they become infected with the new SARS-CoV-2 coronavirus.
The UCSF study was a peer-reviewed and published in the Nicotine And Tobacco Research journal. It analyzed 19 studies on tobacco use among COVID-19 patients in the U.S., China and South Korea.
"The question was what were the chances that they would get worse, for example have to go into the ICU or die," said Professor Stanton Glantz, director of UCSF's Center for Tobacco Control Research and Education. Prof. Glantz co-authored the study with UCSF's Dr. Roengrudee Patanavanich.
The team analyzed data on 11,590 COVID-19 patients in the studies.
The study found about 18.4% of patients got progressively worse. Among those, people with a history of smoking had nearly twice the risk of disease progression, with more critical conditions or death.
"All of them when you take them together, found that when you smoked, it doubled your risk of COVID getting worse, once you got it," said Prof. Glanz.
Glantz says smoking causes an inflammatory response in the lung tissue, which could make it more vulnerable to the coronavirus.
Recently, two French scientists published a hypothesis that nicotine might help protect people from the new coronavirus. The idea is based on data that showed the percentage of smokers with COVID-19 was far less than the percentage of smokers in the overall population.
Professor Glantz says his study also found just 3.6% of U.S. COVID-19 patients were smokers, compared to 13.7% of the U.S. population according to data from 2018.
He suspects the reason is due to under-counting, not due to any protective effect of nicotine.
"A lot of these people are showing up at hospitals very, very sick. They might not even be conscious," said Glantz, "The reliability of assessing smoking status in these emergency situtations is very, very low."
The French scientists are now doing tests with nicotine patches. French officials and Prof. Glantz say right now, there is no data to show nicotine is effective
"I'll be shocked if that turns out to be the case."
Glantz also notes that nicotine patches deliver the drug directly into your bloodstream, compared to smoking where the nicotine is inhaled into the lungs as one of thousands elements in the smoke.
Meantime, he has an hypothesis of his own about smoking and COVID-19.
"I think that the low smoking rates we have here in California, because of the state's anti-smoking program, is contributing to the fact that California is doing relatively well in terms of keeping COVID infections and deaths down," said Glantz.
He noted that the study did not look at vaping or e-cigarettes, so there is still more data to collect.
Professor Glantz says at UCSF they are collecting more data on smoking and infections. H said he hopes to have more analysis in the coming months.