SAN FRANCISCO (CBS SF) — Smoking significantly worsens COVID-19 symptoms, according to a new analysis by UC-San Francisco of the association between smoking and progression of the infectious disease.

In a meta-analysis of studies that included 11,590 COVID patients, researchers found that among people infected with the virus, the risk of disease progression in those who currently smoke or previously smoked was nearly double that of non-smokers.

They also found that when the disease worsens, current or former smokers had more acute or critical conditions or death.

Overall, UCSF reseachers said, smoking was associated with almost a doubling of the risk of disease progressing to more severe conditions.

“Smoking is associated with substantially higher risk of COVID-19 progression,” said Stanton A. Glantz, PhD, professor of medicine and director of the UCSF Center for Tobacco Control Research and Education.

Smoking and e-cigarette use increase the risk and severity of pulmonary infections because of damage to upper airways and a decrease in pulmonary immune function in general, UCSF researchers said.

Although these effects have not yet been studied for COVID-19, smokers have a known higher risk of infection and mortality from MERS, a viral respiratory illness caused by a different coronavirus.

The researchers pulled data from 19 peer-reviewed scientific papers that included data on smoking behavior and severity of COVID-19. The studies, from China, Korea and the United States, were mostly based on hospitalized patients, although two studies included both hospitalized patients and outpatients.

All 19 studies were of patients who had already developed COVID-19, so the risk estimate report does not represent the effect of smoking on the risk of contracting COVID-19 in the general population.

As population-level testing ramps up, the UCSF researchers said it would be useful to collect data on smoking and e-cigarette use to determine what risks these behaviors impose on infection.

A total of 11,590 patients were ultimately identified for the study: 2,133 (18 percent) experienced disease progression, and 731 (6.3 percent) had a history of smoking. Among smokers, 218 patients (29.8 percent) experienced disease progression, compared with 17.6 percent of nonsmoking patients.

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