Effects of smoking intensity and cessation on inflammatory markers in a large cohort of active smokers

Abstract

Background: Cigarette smoking has been associated with increases in C-reactive protein (CRP) and leukocyte counts (white blood cell [WBC]); however, the effects of smoking intensity and smoking cessation on inflammatory markers have not been evaluated prospectively in a large, modern cohort of current smokers.

Methods: White blood cell count and high-sensitivity CRP were measured in current smokers enrolled in a randomized, prospective clinical trial of 5 smoking cessation pharmacotherapies. Smoking intensity parameters included cigarettes per day, pack-years, Fagerström Test of Nicotine Dependence score, and carbon monoxide levels. C-reactive protein also was measured after 1 year with assessment of abstinence status.

Results: The 1,504 current smokers (58% female) were (mean [SD]) 44.7 (11.1) years old, smoked 21.4 (8.9) cigarettes per day, and had a smoking burden of 29.4 (20.4) pack-years. Log(CRP) was not associated with any marker of smoking intensity, except for a weak correlation with pack-years (r = 0.05, P = .047). In contrast, statistically significant correlations were observed between all 4 markers of smoking intensity and WBC count (all P ≤ .011). In multivariable models, waist circumference (P < .001) and triglycerides (P < .05), but no markers of smoking intensity, were associated with log(CRP). However, pack-years (P = .002), cigarettes per day (P = .013), carbon monoxide (P < .001), and Fagerström Test of Nicotine Dependence (P < .001) were independently associated with WBC count. After 1 year, log(CRP) (P = .296) and changes in log(CRP) (P = .455) did not differ between abstainers and continuing smokers.

Conclusions: Smoking intensity is associated with increased WBC count, but not CRP levels. Smoking cessation does not reduce CRP. The relationship between CRP and smoking intensity may be masked by CRP's stronger relationship with adiposity.