Smoking history tied to worse COVID-19 outcomes

(HealthDay)—Cumulative cigarette smoke exposure is an independent risk factor for hospital admission and death from COVID-19, according to a research letter published online Jan. 25 in JAMA Internal Medicine.

Katherine E. Lowe, from the Cleveland Clinic Lerner College of Medicine, and colleagues evaluated the association between cumulative smoking exposure, as measured by pack-years, and the outcomes for 7,102 patients who tested positive for COVID-19 between March 8 and Aug. 25, 2020.

The researchers found that 84.8 percent were never smokers, 2.4 percent were current smokers, and 12.8 percent were former smokers. There was a dose-response association noted between pack-years and adverse COVID-19 outcomes, with patients who smoked for more than 30 pack-years having 2.25 times higher odds of hospitalization and 1.89 times higher odds of dying following a COVID-19 diagnosis versus never smokers. The odds for all adverse outcomes were attenuated in the mediation models, in part by comorbidities. Similar odds ratios were seen for both current and former smokers.

"Smoking is imperfectly classified in patient electronic medical records, and former smokers are potentially classified as never smokers, while pack-years may be underrecorded," the authors write. "However, this misclassification is likely to bias the present results toward the null, which would underestimate the association of cigarette smoking on adverse COVID-19 outcomes."

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