Sammendrag
Objectives This study examined the association between
night shift work and risk of breast cancer, overall and
by hormone receptor subtype, among females in the
Norwegian Offshore Petroleum Workers (NOPW) cohort. We
also examined the association of coexposure (chlorinated
degreasers and benzene) and breast cancer risk, and
possible interaction with work schedule.
Design Prospectively recruited case- cohort study within
the NOPW cohort.
Setting Female offshore petroleum workers active on the
Norwegian continental shelf.
Participants 600 female workers (86 cases and 514 non-
cases) were included in the study. We excluded workers
that died or emigrated before start of follow-up, had
missing work history, were diagnosed with breast cancer
or other prior malignancy (except non-melanoma skin
cancer) before start of follow-up.
Results No overall association was found between breast
cancer risk and work schedule (HR 0.87, 95% CI 0.52
to 1.46 for work schedule involving night shift vs day
shift only). There was no significant association between
work schedule and risk of any breast cancer subtype. No
significant interactions were found between work schedule
and chemical coexposures (breast cancer overall Pinteraction
chlorinated degreasers
=0.725 and Pinteraction benzene
=0.175).
Conclusions Our results did not provide supporting
evidence that work schedule involving night shift affects
breast cancer risk in female offshore petroleum workers,
but should be considered cautiously due to few cases.
Further studies with larger sample sizes are warranted
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