Salivary cortisol and sleep problems among civil servants.
OBJECTIVE
The present study used information from a field study conducted among 4489 civil servants (70% women) in Denmark in 2007. The purpose was to examine the association between sleep problems and salivary cortisol by using a cross-sectional design with repeated measures in a subsample three-month later.


METHODS
Sleep problems during the past night and the past 4 weeks were assessed by a self-administered questionnaire on overall sleep quality, disturbed sleep, sleep length and awakening problems. Saliva samples were collected in a single day, using cotton tubes, 30 min after awakening and again at 2000 h. A subsample of 387 participants collected saliva samples three-month later at awakening, +20 min and +40 min after awakening and at 2000 h. We adjusted for confounders related to sampling time, life style and personal characteristics, socioeconomic status and work aspects.


RESULTS
Sleep problems during the past four weeks were associated with low morning and evening saliva cortisol concentrations: [-3.1% per score of disturbed sleep (p=.009); and -4.7% per score of awakening problems (p<.001)]. Whereas sleep problems were not related with slope (the morning to evening change in cortisol levels). Awakening problems predicted lower cortisol (-7.51% per score; p=.003) three-month later. Cortisol awakening response (CAR) and slope three-month later were significantly associated with disturbed sleep (-7.84% and -8.24%) and awakening problems (-6.93). Area under the curve (AUC(morning)) increased with disturbed sleep (3.77%).


CONCLUSIONS
Surprisingly, low morning cortisol was associated with increased sleep problems during a four-week period prior to sampling among 4066 Danish civil servants. At follow-up three-month later, those with sleep problems had a flattened cortisol profile. Those with awakening problems also had low salivary cortisol in general.
The National Research Centre for Working Environment, Copenhagen, Denmark. aamh@nrcwe.dk
Ase Marie
AM
Hansen
Jane Frølund
JF
Thomsen
Anette
A
Kaergaard
Henrik Albert
HA
Kolstad
Linda
L
Kaerlev
Ole
O
Mors
Reiner
R
Rugulies
Jens Peter
JP
Bonde
Johan Hvid
JH
Andersen
Sigurd
S
Mikkelsen
D000328:Adult; D000368:Aged; D003430:Cross-Sectional Studies; D003718:Denmark / Q000453:epidemiology; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis / Q000378:metabolism*; D008297:Male; D008875:Middle Aged; D009787:Occupational Medicine / Q000706:statistics & numerical data; D012463:Saliva / Q000737:chemistry / Q000378:metabolism*; D012893:Sleep Wake Disorders / Q000453:epidemiology* / Q000209:etiology / Q000378:metabolism; D012946:Social Welfare / Q000523:psychology / Q000706:statistics & numerical data*; D012947:Social Work / Q000706:statistics & numerical data*; D055815:Young Adult
D006854:Hydrocortisone