Cotinine, a metabolite of nicotine, is widely used to distinguish smokers from nonsmokers in epidemiologic studies and smoking-cessation clinical trials. As the magnitude of secondhand smoke exposure declines because of proportionally fewer smokers and more clean-indoor-air regulations, the optimal cotinine cutpoint with which to distinguish smokers from nonsmokers is expected to change. The authors analyzed data on 3,078 smokers and 13,078 nonsmokers from the National Health and Nutrition Examination Survey for 1999-2004. Optimal serum cotinine concentrations for discriminating smokers from nonsmokers were determined using receiver operator characteristic curve analysis. Optimal cotinine cutpoints were 3.08 ng/mL (sensitivity = 96.3%, specificity = 97.4%) and 2.99 ng/mL (sensitivity = 86.5%, specificity = 93.1%) for adults and adolescents, respectively. Among adults, optimal cutpoints differed by race/ethnicity: They were 5.92 ng/mL, 4.85 ng/mL, and 0.84 ng/mL for non-Hispanic blacks, non-Hispanic whites, and Mexican Americans, respectively. Among adolescents, cutpoints were 2.77 ng/mL, 2.95 ng/mL, and 1.18 ng/mL for non-Hispanic blacks, non-Hispanic whites, and Mexican Americans, respectively. Use of the currently accepted cutpoint of 14 ng/mL overestimates the number of nonsmokers in comparison with the proposed new overall cutpoint of 3 ng/mL or the race/ethnicity-specific cutpoints of 1-6 ng/mL.

Sleep disturbances resulting in insufficient sleep have been linked to negative physical, cognitive, and public health outcomes. Despite this, there has yet a study that examines the impact of smoking on sleep in a US based national sample. The current study sought to observe sleep disturbances associated with smoking status. Sleep disturbances in adults aged 20 years and above, from the 2005-2006 National Health and Nutrition Examination Survey, were measured among current, former, and never smokers (NS). Current smokers (CS) reported significantly less total sleep time, longer sleep onset latency, increased difficulty falling asleep, maintaining sleep, and waking up earlier than desired when compared to NS. Former smokers reported disturbances similar to NS and CS experienced poorer sleep than nonsmokers. Our study is the first to observe sleep difficulty by smoking status in a large, population-based, nationally representative sample. Recommendations for smoking cessation programs are discussed.