Self-reported smoking, urine cotinine, and risk of cardiovascular disease: Findings from the PREVEND (Prevention of Renal and Vascular End-Stage Disease) prospective cohort study

Abstract

Background--We aimed to compare the associations of smoking exposure as assessed by self-reports and urine cotinine with cardiovascular disease (CVD) risk and determine the potential utility of cotinine for CVD risk prediction. Methods and Results--Smoking status by self-reports and urine cotinine were assessed at baseline in 4737 participants (mean age, 53 years) of the PREVEND (Prevention of Renal and Vascular End-Stage Disease) prospective study. Participants were classified as never, former, light current (≤ 10 cigarettes/day), and heavy current smokers (> 10 cigarettes/day) according to self-reports and analogous cutoffs for urine cotinine. During a median follow-up of 8.5 years, 296 first CVD events were recorded. Compared with selfreported never smokers, the hazard ratios (95% confidence interval) of CVD for former, light current, and heavy current smokers were 0.86 (0.64-1.17), 1.28 (0.83-1.97), and 1.80 (1.27-2.57) in multivariate analysis. Compared with urine cotinine-assessed never smokers, the corresponding hazard ratios of CVD for urine cotinine-assessed former, light current, and heavy current smokers were 1.70 (1.03-2.81), 1.62 (1.15-2.28), and 1.95 (1.39-2.73) respectively. The C-index change on adding urine cotinine-assessed smoking status to a standard CVD risk prediction model (without self-reported smoking status) was 0.0098 (0.0031-0.0164; P=0.004). The corresponding C-index change for self-reported smoking status was 0.0111 (0.0042-0.0179; P=0.002). Conclusions--Smoking status as assessed by self-reports and urine cotinine is associated with CVD risk; however, the nature of the association of urine cotinine with CVD is consistent with a dose-response relationship. The ability of urine cotinine to improve CVD risk assessment is similar to that of self-reported smoking status.