Objectives To investigate cross-sectional and longitudinal associations between self-reported exhaustion and diurnal levels of saliva cortisol.

Methods In a two wave cohort study of public service employees (baseline 2007, follow-up 2009), cortisol in saliva was measured in the morning and in the evening and exhaustion was measured by the scale of general burnout from the Copenhagen Burnout Inventory (six items on exhaustion, scored 1 to 5 (never, seldom, sometimes, often, always)). The material for cross-sectional analyses consisted of 3614/4000 and 2489/2813 persons with valid burnout and cortisol data morning/evening in 2007 and 2009, respectively. The corresponding material for longitudinal analyses included 2115/2588 persons. The natural log of cortisol was analysed as the dependent variable with exhaustion as the explaining variable in a model with mutually adjusted cross-sectional and longitudinal effects and adjustment for age, gender, saliva sampling times and awakening time.

Results Cross-sectionally, high levels (often or always) of exhaustion was experienced by 8% of the study population, and the ratio of their morning cortisol level compared to those with the lowest levels of exhaustion was 0.90 (95% confidence interval 0.84–0.97, p = 0.008). The same tendency was found for evening cortisol, but this finding was not significant after adjustment. Exhaustion did not change the slopes of morning cortisol concentrations with saliva sampling time since awakening. There were no significant longitudinal effects.

Conclusions High levels of exhaustion was associated with low morning cortisol levels in cross-sectional analyses but not in longitudinal analyses.