The relationship between smoking status and cortisol secretion

Context: Evidence for an association of smoking status with cortisol secretion is mixed. Objective: The objective of the study was to assess the relationship between smoking status and salivary cortisol. Design: This was a cross-sectional study of smoking status and cortisol secretion from phase 7 (2002-2004) of the Whitehall II study. Setting: An occupational cohort was originally recruited in 1985-1987. Participants: The study population consisted of 3103 men (1514 never-smokers, 1278 ex-smokers, and 311 smokers) and 1128 women (674 never-smokers, 347 ex-smokers, and 107 smokers). Information was collected on smoking status, average number of cigarettes smoked, and additional covariates. Outcome Measures: Saliva samples were taken on waking; waking + 0.5, 2.5, 8, and 12 h; and bedtime for the assessment of cortisol. Results: Smoking status was significantly associated with increased salivary cortisol release throughout the day (P < 0.001) adjusted for covariates; this was apparent for the cortisol awakening response (P < 0.001) when examined separately. Compared with never-smokers, smokers had higher release of total cortisol (P = 0.002), whereas no difference was observed between never-smokers and ex-smokers (P = 0.594): mean release per hour (nanomoles per liter), never-smokers, 4.13 [confidence interval (CI) 4.02-4.24]; ex-smokers, 4.21 (CI 4.08-4.35); smokers, 4.63 (CI 4.35-4.93). There was no significant relationship between number of cigarettes smoked and total cortisol release. However, a difference was observed for the cortisol awakening response: mean release by tertiles of cigarettes smoked (nanomoles per liter): high, 13.49 (CI 10.74-16.23); medium, 9.58 (CI 7.40-11.76); low, 8.49 (CI 5.99-10.99), P = 0.029. Conclusion: Salivary cortisol is increased in current smokers, compared with nonsmokers; no differences were observed between ex-smokers and never-smokers, suggesting that smoking has a short-term effect on the neuroendocrine system.