The effect of smoking on COVID‐19–linked biomarkers in hospitalized patients with COVID‐19

BACKGROUND: The coronavirus pandemic, an infection (coronavirus disease 2019—COVID‐19), caused by severe acute respiratory disease coronavirus 2 (SARS‐CoV‐2), continues to have a strong influence worldwide. Although smoking is a major known risk factor for respiratory infectious disease, the effects of smoking on COVID‐19 are unclear. In this study, we aimed to evaluate the relationship between smoking and important hematologic (lymphocyte count, neutrophil count, platelet count, neutrophil‐lymphocyte ratio [NLR], platelet‐lymphocyte ratio [PLR]), inflammatory, and biochemical biomarkers in the prognosis of hospitalized patients with COVID‐19. METHODS: In a COVID‐19 pandemic hospital between June and August 2020, 200 adult patients aged over 18 years were hospitalized with COVID‐19 inflammatory and hematologic biomarkers at their first admission and smoking data were selected for this study. RESULTS: The rate of smokers was much higher among men (91.5%) than in women (8.5%) (p = 0.001). Neutrophil counts were evaluated and was significantly higher in current smokers (p < 0.001) and ex‐smokers (p = 0.001), and NLR (p = 0.008) and ferritin (p = 0.004) levels were higher than in never smokers. The saturation of patients had a negative significant linear correlation of NLR, PLR, and pack years of smoking. Compared with never smokers, current smokers had higher neutrophil counts (OR = 0.828 [0.750–0.915]; p = 0.041), NLR values (OR = 0.948 [0.910–0.987]; p = 0.009), and CRP levels (OR = 0.994 [0.990–0.999]; p = 0.019). CONCLUSION: Serum neutrophil, NLR, and ferritin levels, which are widely used in determining the prognosis of COVID‐19, were found higher in current smokers/ex‐smokers. These results support the view that a poor prognosis of COVID‐19 is associated with smoking.