Abstract
BACKGROUND: Sleep problems are linked with negative health outcomes, including coronary heart disease. Neuroendocrine dysfunction has been associated with sleep problems and may be a pathway linking sleep and ill health. Dysregulated cortisol output has observed in people with type 2 diabetes (T2D), though little is known about the links between sleep and cortisol in this population at high risk of coronary disease. METHOD: This study investigated the association between sleep problems and cortisol over the course of an ordinary day and in response to acute laboratory stress in a sample of 129 individuals with T2D. Sleep problems were assessed using the Jenkins sleep problems questionnaire. Mental stress was induced using two five-minute laboratory stress tasks: a mirror-tracing task and the Stroop color-word interference task. RESULTS: Sleep problems were positively associated with daily cortisol area under the curve (B = 17.051, C.I. = 6.547 to 27.554, p = 0.002) adjusting for age, sex, marital status, education, household income, body mass index and smoking; suggesting that those with greater sleep problems had greater cortisol concentrations over the course of an ordinary day. Participants reporting greater sleep problems also had raised evening cortisol levels (B = 0.96, C.I. = 0.176 to 1.746, p = 0.017) in adjusted models. In the laboratory sleep problems were negatively associated with cortisol immediately post-task (B = -0.030, C.I. = -0.059 to 0.000, p = 0.048) and 45 minutes post-task (B = -0.037, C.I. = -0.072 to -0.002, p = 0.039) in fully adjusted models; indicating that those who experienced greater sleep problems had lower cortisol concentrations after stress. CONCLUSIONS: Sleep problems were associated with disturbances in cortisol responses to stress, as well as changes diurnal cortisol output in people with T2D. Further research is needed to assess if neuroendocrine disturbance increases the risk of cardiovascular disease in this population.