The relationship between smoking status and cortisol secretion.
Evidence for an association of smoking status with cortisol secretion is mixed. The objective of the study was to assess the relationship between smoking status and salivary cortisol. This was a cross-sectional study of smoking status and cortisol secretion from phase 7 (2002-2004) of the Whitehall II study. An occupational cohort was originally recruited in 1985-1987. 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. Saliva samples were taken on waking; waking + 0.5, 2.5, 8, and 12 h; and bedtime for the assessment of cortisol. 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. 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.