Title: Leukocytosis and Tobacco Use: A Risk Assessment
Abstract: I read the paper by Smith et al1Smith CJ, Kluck LA, Ruan GJ, et al. Leukocytosis and tobacco use: an observational study of asymptomatic leukocytosis. Am J Med in press.Google Scholar with great interest. The authors evaluated the change of white blood cell count after smoking cessation. The authors selected 40 subjects having leukocytosis. The mean body mass index was 31.5 kg/m2, and 24 patients were female. During longitudinal follow-up, 9 subjects quit and 2 subjects reduced tobacco use. There was a significant decrease in mean white blood cell count of 11 subjects (from 13.2 × 109/L to 11.1 × 109/L), and the median time to decrease in white blood cell count was 8 weeks (ranging from 2 to 49 weeks). I have a query about their study. First, Abel et al2Abel GA Hays JT Decker PA Croghan GA Kuter DJ Rigotti NA Effects of biochemically confirmed smoking cessation on white blood cell count.Mayo Clin Proc. 2005; 80: 1022-1028Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar determined the relationship between total white blood cell count and absolute neutrophil counts after smoking cessation. After 7 weeks, there was a significant decrease in white blood cell indices in continuously abstinent subjects compared with continuing smokers. At 52 weeks, declines from baseline in mean white blood cell count and mean neutrophil counts were 1.2 × 109/L and 1.0 × 109/L, which would reflect a remarkable decrease in an underlying state of tobacco-induced inflammation. Second, I previously conducted a cross-sectional study to investigate the associations between smoking and leukocytosis or elevated hemoglobin (Hb) concentrations in male subjects.3Kawada T. Smoking-induced leukocytosis can persist after cessation of smoking.Arch Med Res. 2004; 35: 246-250Crossref PubMed Scopus (36) Google Scholar Adjusted odds ratios (ORs) (95% confidence intervals [CIs]) of current smokers and ex-smokers with a period of 5-9.9 years since smoking cessation vs. non-smokers for white blood cell count of >9.0 × 109/L in total blood were 12.1 (7.0-21.0) and 3.8 (1.2-12.0), respectively. In addition, adjusted OR (95% CI) of current smokers vs. non-smokers for Hb level of >16 g/dL in total blood was 1.6 (1.1-2.3). I concluded that current smokers and ex-smokers for 5-9.9 years both presented an increase in white blood cell count, which presented persistent smoking-induced leukocytosis after smoking cessation. The level of effect size in ex-smokers was smaller than that in current smokers, and there was no significance in OR of ex-smokers for Hb level of >16 g/dL. I understand that these data would present desirable effects of smoking cessation on health. Differences in study design and sex composition may partly contribute to the discrepancy regarding the relationship between smoking cessation and white blood cell count. I agree that smoking cessation would contribute to lowering tobacco-induced inflammation. However, caution should be paid to the level of decrease in white blood cell count. Both Smith et al1Smith CJ, Kluck LA, Ruan GJ, et al. Leukocytosis and tobacco use: an observational study of asymptomatic leukocytosis. Am J Med in press.Google Scholar and Abel et al2Abel GA Hays JT Decker PA Croghan GA Kuter DJ Rigotti NA Effects of biochemically confirmed smoking cessation on white blood cell count.Mayo Clin Proc. 2005; 80: 1022-1028Abstract Full Text Full Text PDF PubMed Scopus (36) Google Scholar provide evidence that absolute values of white blood cell count or neutrophil count remain higher in ex-smokers than those in non-smokers, and I recommend long-term monitoring of leukocytosis to prevent adverse health effects. The ReplyThe American Journal of MedicineVol. 134Issue 3PreviewIt was with great interest that we reviewed the correspondence by Dr. Kawada about our recent study of tobacco smoking and leukocytosis.1 The author highlighted our findings of reduction in total white blood cell count during longitudinal follow-up in 11 subjects who either quit (n = 9) or reduced (n = 2) tobacco use. Full-Text PDF