Smokers have a significantly higher hospitalization with Covid-19 and mortality rate than non-smokers. In previous studies, this correlation was partly not proven because not the cumulative smoke dose but only the patients’ current habits were taken into account.
Ohio (U.S.A.). A study with health data from China already provided evidence in March 2020 that smoking significantly increases the risk of a severe disease course with Covid-19. A survey conducted by the UCLA, University of California identified the cause of this: smoking inhibits the formation and maturation of airway stem cells.
However, some studies also came to contrary results, according to which smoking is not an obvious risk factor for a severe course of Covid 19 disease. These studies caused controversy since SARS-CoV-2 infects the lungs and the endothelium of the blood vessels, which are too stressed by smoking in medicine.
Inaccurate Information On Smoking Behavior
One possible reason for these conflicting study results could be inaccurate information in patient health records. In many clinics, doctors only ask about current habits, but do not consider whether a patient has been a (heavy) smoker in the past. The decisive factor is that smoking is the cumulative dose, i.e. the number of cigarettes that a person has consumed during his life.
Cumulative Smoke Dose Studied
Scientists from the Cleveland Clinic have included information on the cumulative smoke dose in patient files since March 2020 as part of the Covid 19 pandemic. So far, 7,102 patients have been recorded, of which 910 were former, and 172 were active smokers. Three hundred forty-one of these people have a cumulative smoke dose of at least 30 pack years.
According to an analysis of the health data published in the journal JAMA Internal Medicine, this group’s hospitalization rate was 4.65 times higher than that of non-smokers. They also had to be treated 2.11 times more often and had 6.2 times higher risk of death.
Older Age Of Long-Term Smokers
According to the researchers, part of the increased risk is due to the significantly higher age of long-term smokers on average. If factors such as age, gender and ethnic origin are factored out, the risk of hospitalization for more than 30 pack-years (odds ratio 2.25; 95% confidence interval 1.76 to 2.88), intensive care treatment ( Odds ratio 1.69; 1.23 to 2.35) and death from Covid-19 (odds ratio 1.89; 1.29 to 2.76) but still significantly higher.
According to further analyzes, the higher risk is mainly due to comorbidities of smoking. Thirty pack years caused arterial hypertension in 85.5 per cent of the mean 71-year-old patients. Besides, 47.2 per cent had emphysema or COPD, 43.1 per cent had coronary heart disease, 32.3 per cent had cardiac insufficiency, and 30.8 per cent had cancer (past and current), and 22.9 per cent had asthma.