Neutrophil/lymphocyte ratio is correlated with levels of inflammatory markers and is significantly reduced by smoking cessation

Previous studies have reported that the neutrophil to lymphocyte ratio (NLR) is associated with onset and prognosis of cardiovascular disease (CVD). Smoking is a major risk factor for CVD and smoking cessation significantly reduces CVD risk. However, the effects of smoking cessation on the NLR remain unknown. Among smokers visiting our smoking cessation clinics, we examined changes in the NLR and CVD biomarkers before and after smoking cessation. A total of 389 individuals (301 men and 88 women) were enrolled in the study. The median NLR was significantly reduced after successful smoking cessation (before: 1.8, interquartile range [IQR] 1.5, 2.5; after: 1.7, IQR 1.3, 2.4). In a linear regression model adjusted for sex, percent change in NLR comparing before and after smoking cessation was significantly and positively correlated with percent changes in C-reactive protein (β = 0.260), α1-antitrypsin-low density lipoprotein (β = 0.151, p < 0.05), and serum amyloid A-low density lipoprotein (β = 0.325). Our study demonstrated for the first time that smoking cessation significantly reduces the NLR in tandem with markers of inflammation and oxidative stress.