The association between long-term accumulation of temporary employment, the cortisol awakening response and circadian cortisol levels

Temporary employment is an increasingly common contract type, which has not been investigated in a psychoneuroendocrinological context despite previous observations of associations between adverse work and employment conditions and hypothalamic-pituitary-adrenal (HPA) axis dysregulations. The present study aims to examine whether the 12-year accumulation of temporary employment is related to circadian cortisol levels, and if any association is independent of current employment conditions. Participants were drawn from the prospective Northern Swedish Cohort (n=791, 74% of the original cohort). At age 43 years, retrospective reports of employments over the last 12 years and of current social conditions were collected by questionnaire, and one-day salivary cortisol profile was measured (at awakening, +15 min post-awakening, pre-lunch, bedtime). Results indicated a gradually higher magnitude of the cortisol awakening response (CAR) in subjects with no (0 months in temporary employment; mean CAR=34%), moderate (1-25 months in temporary employment; mean CAR=41%) and heavy (>25 months in temporary employment; mean CAR=51%) exposure (p=.020), remaining after adjustment for potential confounders and for current employment conditions (p=.028). The higher CAR was explained by lower awakening rather than higher post-awakening cortisol levels. Cortisol levels at all times of the day except post-awakening displayed tendencies to negative relations to temporary employment; as indicated by a lower Area Under of Curve (regression coefficient=5.0%, p=.038 after adjustment). This study thus suggests that the long-term exposure to temporary employment might confer HPA dysregulations in the form of increased dynamics of the CAR and circadian suppression.