Analysis of salivary cortisol levels to determine the association between depression level and differences in circadian rhythms of shift-working nurses.
OBJECTIVE
The aim of this study was to clarify whether there are differences in the circadian rhythms of shift-working nurses by assessing depression, fatigue and salivary cortisol levels.


METHODS
Forty nurses working in a two-shift system at "Hospital A", Fukuoka City, Japan, used a self-rated depression scale (SDS) to assess their depression levels. Fatigue levels were measured with the visual analogue scale for fatigue (VAS-F); saliva was collected before and during shifts for three days. Results were analyzed with analysis of variance (ANOVA).


RESULTS
Thirty-six valid records were obtained, and subjects were classified according to SDS scores into a normal group (NG), moderate group (MG) and severe group (SG). There were no significant differences in the day shift salivary cortisol values of the three groups. However, the night shift salivary cortisol value for the SG was 0.132 µg/dl at 16:00, before starting the shift, and decreased to 0.036 µg/dl at 20:00. It increased slightly up to 0.057 µg/dl by 24:00 and formed a peak between 5:00 and 7:00, with the levels being 0.322 µg/dl and 0.305 µg/dl respectively. Meanwhile, the NG cortisol value was 0.154 µg/dl before the shift, decreased to 0.034 µg/dl by 20:00, slightly increased up to 0.093 µg/dl by 5:00 and presented its peak value, 0.253 µg/dl, at 7:00 next morning.


CONCLUSIONS
SG nurses presented significantly increased salivary cortisol levels early in the morning during night shifts, showing a phase deviation in the circadian rhythm. Because subjective fatigue levels did not differ with time, SG nurses should understand and deal with physical changes in the early morning. This approach may reduce medical accidents and malpractice in the early morning.
School of Nursing, Faculty of Medicine, Fukuoka University.
Michie
M
Baba
Mitsuru
M
Ohkura
Kayoko
K
Koga
Kyoko
K
Nishiuchi
Lourdes R
LR
Herrera
Ryoichi
R
Matsuse
Toshitaka
T
Inoue
D000328:Adult; D000704:Analysis of Variance; D002940:Circadian Rhythm / Q000502:physiology*; D003863:Depression / Q000503:physiopathology* / Q000523:psychology; D005221:Fatigue / Q000503:physiopathology / Q000523:psychology; D005260:Female; D006801:Humans; D006854:Hydrocortisone / Q000032:analysis*; D007564:Japan; D008297:Male; D008875:Middle Aged; D009741:Nursing Staff, Hospital / Q000523:psychology* / Q000706:statistics & numerical data; D012463:Saliva / Q000737:chemistry*; D064232:Visual Analog Scale; D014940:Work Schedule Tolerance / Q000502:physiology* / Q000523:psychology; D055815:Young Adult
D006854:Hydrocortisone