- More evidence of the severity of Covid-19 in smokers globally
- Analysis looked at data involving more than 11 000 patients
- As the disease progresses in smokers, higher risk of death seen
Covid-19 hits smokers much harder than nonsmokers, according to a new review.
Researchers from the University of California, San Francisco (UCSF), analysed 19 studies that included data on smoking and severity of Covid-19 among nearly 11 600 patients in the United States, China and Korea.
Most patients were hospitalised, but two studies also included outpatients. Just over 6% of participants had a history of smoking.
While Covid-19 symptoms worsened in 18% of all patients, the rate was 29.8% among current or former smokers, compared with 17.6% among non-smokers.
Higher risk of death
"Smoking is associated with substantially higher risk of Covid-19 progression," said study co-author Stanton Glantz, director of the Center for Tobacco Control Research and Education at UCSF.
And when Covid-19 progressed, current or ex-smokers had more acute or critical conditions and a higher risk of death, the researchers found.
"This finding suggests that California's ongoing strong tobacco control measures that have lowered smoking may, together with the state's other strong public health interventions, be contributing to California's efforts to thwart the effect of Covid-19," Glantz said in a university news release.
Co-author Dr Roengrudee Patanavanich, a visiting scholar at UCSF, noted that the fact tobacco use is lower among Covid patients than the general population has been cited as evidence for a protective effect of smoking.
Lower immune function
"But this low prevalence may actually be due to an under-assessment of smoking, especially when you consider the difficult conditions involved when caring for people in often overwhelmed health systems," said Patanavanich, of Ramathibodi Hospital at Mahidol University in Bangkok, Thailand.
Tobacco and electronic cigarettes both damage the upper airways and dampen immune function, which increases smokers' risk and severity of lung infections, according to the researchers.
Quitting smoking and e-cigarettes should be added to the list of measures to combat the Covid-19 pandemic, the authors suggested.
The study was published on 13 May in the journal Nicotine & Tobacco Research.
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