Heavy smoking history increases risk for COVID-19 hospitalization, death

The longer an individual smoked, the greater his or her odds were for COVID-19 hospitalization and death, an analysis of data from a single health system showed.

The link between smoking and COVID-19 severity remains unclear. The authors of a systematic review and meta-analysis published in July said smoking moderately increased the risk for severe COVID-19, contradicting a conclusion made by the authors of another systematic review and meta-analysis from April, which found no significant link.

In the new study, Katherine E. Lowe, MSc, of Cleveland Clinic’s Lerner College of Medicine of Case Western Reserve, and colleagues compared COVID-19 severity among never smokers (n = 6,020; mean age, 47.8 years; 61.2% women) with those reporting 0 to 10 pack-years of smoking (n = 341; mean age, 56.4 years; 56% women), 10 to 30 pack-years of smoking (n = 400; mean age, 65.2 years; 53% women) and more than 30 pack-years of smoking (n = 341; mean age, 71 years; 42.5% women). According to the National Cancer Institute, pack-years are defined as the number of packs of cigarettes a person smokes daily multiplied by the number of years the person has smoked.

Lowe and colleagues reported that patients who smoked more than 30 pack-yearshad 2.25 times higher odds for hospitalization (95% CI, 1.76-2.88) than those who never smoked. These “heavy smokers” were also 1.89 times more likely to die following a COVID-19 diagnosis (95% CI, 1.29-1.76) compared with never smokers, according to the researchers.

“The association between cumulative smoking and adverse COVID-19 outcomes is likely mediated in part by comorbidities,” Lowe and colleagues wrote in JAMA Internal Medicine. “The odds ratios for all adverse outcomes were attenuated in the mediation models. There was no evidence of effect modification by smoking status; similar odds ratios were seen in both current and former smokers.”

The researchers acknowledged that patients’ smoking history is not always correctly documented in their electronic health records.

“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,” Lowe and colleagues wrote.

They said unequal access to health care may have affected the collection of patient data.

“Nevertheless, we have demonstrated in this single central registry of patients who tested positive for COVID-19 that increased cumulative smoking was associated with a higher risk of hospitalization and mortality from COVID-19 in a dose-dependent manner,” Lowe and colleagues wrote.

Reference:

Pack-year. National Cancer Institute. https://www.cancer.gov/publications/dictionaries/cancer-terms/def/pack-year. Accessed January. 21, 2021.