Is Serum Cotinine a Better Measure of Cigarette-Smoking Than Self-Report?

Objectives. To address the question of whether serum cotinine is a better measure of cigarette smoking than self-reported behavior by examining the relation of biochemical, physical examination, and depression assessments to self-reported cigarette consumption and serum cotinine in a population-based sample. Methods. Serum from 743 Mexican American participants in the Hispanic Health and Nutrition Examination Survey (HHANES) categorized by sex and number of cigarettes smoked per day (0, 1 to 9, 10 to 19, ≥ 20) was analyzed for cotinine. HHANES results from hematocrit, hemoglobin, red blood cells (RBCs), white blood cells (WBCs), mean corpuscular volume (MCV), iron, transferrin, lead, erythrocyte protoporphyrin (EPP), vitamin E, vitamin A, cholesterol, body mass index (BMI), pulse rate, systolic and diastolic blood pressure (DBP), Center for Epidemiological Depression Scale (CES-D), and Diagnostic Interview Schedule (DIS) depression diagnosis were compared by category of cigarettes smoked per day and serum cotinine. Results. Among women significant correlations were found between cigarettes per day and cotinine, respectively, and hematocrit (r = 0.148, r = 0.338), hemoglobin (r = 0.152, r = 0.342), WBCs (r = 0.160, r = 0.272), and BMI (r = −0.124, r = −0.164). Among men significant correlations were found between cigarettes per day and cotinine, respectively, and WBCs (r = 0.176, r = 0.296), MCV (r = 0.310, r = 0.264), lead (r = 0.105, r = 0.177), and BMI (r = −0.110, r = −0.192). Cotinine, but not cigarettes per day, was significantly correlated with hemoglobin (r = 0.179) and DBP (r = −0.146) in men and EPP (r = −0.135) and cholesterol (r = 0.105) in women. Mean CES-D score was correlated with cigarettes per day for both men (r = 0.106) and women (r = 0.158) but not with cotinine. CES-D caseness (score ≥ 16) and a positive diagnosis of depression by DIS was not related to smoking behavior measures among men. Women smokers compared to nonsmokers had higher levels of depression. Multivariate regression models controlling for sex, age, and education indicated that serum cotinine was a significant predictor of hematocrit, hemoglobin, RBCs, WBCs, lead, and DBP; self-reported cigarettes was significant only for MCV. Conclusions. Serum cotinine may be a better method of quantifying risks from cigarette use in epidemiological studies.