Study objectives: To assess the effect of continued smoking and smoking reduction on cardiovascular biomarkers (eg, WBC count, cholesterol concentrations, BP, heart rate).
Design, setting, and participants: This study, conducted at the University of Minnesota, randomized smokers interested in significantly reducing cigarette use but not quitting to either start 12 weeks of smoking reduction immediately (n = 102), assisted by nicotine replacement therapy, or to a 6-week wait list (n = 49). Those starting smoking reduction were required to reduce smoking by 25% for 2 weeks, 50% for 2 weeks, and 75% during the final 2 weeks. After 6 weeks, the subjects were asked to maintain a 50% reduction or quit. Nicotine gum and, if necessary, nicotine patch were used to achieve reduction goals. The wait list group (n = 49) smoked ad libitum for 6 weeks and then reduced smoking as previously described.
Measurements and results: Cardiovascular biomarkers (eg, WBC count, cholesterol concentrations, BP, heart rate) were assessed at several time points after enrollment. During ad libitum smoking, cardiovascular biomarkers remained relatively stable with correlation coefficients across the various time measurements, ranging from 0.44 to 1.00 (p < 0.01 for all measures). Among successful nonabstinent reducers (64 of 151 subjects), significant improvements were found in many biomarkers (eg, hemoglobin, hematocrit, RBC and WBC counts, lipids, BP, heart rate, respiratory symptoms, all p < 0.0167).
Conclusions: These results show the availability of reliable and dose-sensitive biomarkers and that reduction in smoking can lead to significant but only modest changes in cardiovascular risk factors in healthy smokers. It is not known whether the reductions in cardiovascular risk factors observed after smoking reduction are also associated with reduced disease risk. Additional research is necessary to address this issue.