Twenty-four-hour light exposure and melatonin levels among shift workers.
OBJECTIVE
We sought to measure melatonin levels and 24-hour light intensity exposure in health care workers over a 7-day period in natural occupational and residential settings.


METHODS
Five office workers and 17 nurses working either days or rotating night and day shifts wore a device to record light intensity exposure for one or two 7-day periods, completed a questionnaire, and provided three saliva samples for melatonin.


RESULTS
Rotating shift workers had irregular light exposure patterns and abnormal melatonin levels compared with those working days. In addition to lower-than-normal melatonin levels during sleep periods, rotating shift workers exhibited higher-than-normal melatonin levels on arising and during work. Self-reported years of shift work were correlated with measured melatonin and light.


CONCLUSIONS
Rotating shift work is supported as a surrogate for exposure to light-at-night and circadian disruption.
Borugian
Marilyn J
MJ
Cancer Control Research Program, British Columbia Cancer Research Centre, Vancouver, British Columbia, Canada. mborugian@bccrc.ca
Gallagher
Richard P
RP
Friesen
Melissa C
MC
Switzer
Teresa F
TF
Aronson
Kristan J
KJ
D000328:Adult; D005260:Female; D006282:Health Personnel; D006801:Humans; D008027:Light; D008297:Male; D008550:Melatonin / Q000032:analysis*; D008875:Middle Aged; D016273:Occupational Exposure; D012463:Saliva / Q000737:chemistry; D013997:Time Factors
D008550:Melatonin