The effects of cigarette smoking on CRP concentrations in men and women and its modification by exogenous oral hormones in women

BACKGROUND: Previous studies have shown dose-dependent and time-dependent effects of cigarette smoking and smoking cessation on C-reactive protein (CRP) concentrations in men, but results were inconsistent for women. The aim of this study was to evaluate the dose-dependent and time-dependent association of smoking and smoking cessation with CRP concentrations in men and women using a novel comprehensive smoking index (CSI). DESIGN: Cross-sectional study of representative US survey data (National Health and Nutrition Examination Survey 1999-2002). METHODS: The CSI simultaneously accounts for intensity, duration and time since cessation of smoking. We analyzed data of 3505 men and 3896 women using sex-specific multiple linear regression models adjusting for other determinants of CRP concentrations, including age, race/ethnicity, body mass index, alcohol intake, diabetes, physical activity, oral hormone use among women, and history of coronary heart disease, stroke, chronic obstructive pulmonary disease and arthritis. RESULTS: A positive association of similar strength was found between smoking and CRP concentrations in both men and women who did not use exogenous oral hormones. Among women who used exogenous oral hormones, no association with smoking was found. In older men and women it took several years after smoking cessation for CRP concentrations to return to that of individuals who never smoked. CONCLUSION: Smoking is associated with dose-dependent and time-dependent increases in CRP concentrations in both men and women. Furthermore, the effect of exogenous oral hormones on CRP concentrations in women is affected by smoking in a dose-dependent fashion.