Night shifts up cancer risk in women

20.09.2013 14:39

LONDON: Working night shifts for more
than 30 years can double a woman's risk
of developing breast cancer, scientists
have warned.
In a study published in the British
Medical Journal, Canadian researchers
assessed whether night shifts were linked
to an increased risk of breast cancer.
They studied 1,134 women with breast
cancer and 1,179 women without the
disease, but of the same age, in
Vancouver , British Columbia, and
Kingston, Ontario.
Shift work has been suggested as a risk
factor for breast cancer, but there has
been some doubt about the strength of
the findings, largely because of issues
around the assessment of exposure and
the failure to capture the diversity of shift
work patterns. Several previous studies
have also been confined to nurses rather
than the general population.
The women, who had done various
different jobs, were asked about their
shift work patterns over their entire work
history; hospital records were used to
determine tumour type.
This may be important, said the authors,
because risk factors vary according to
hormone sensitivity, and the sleep
hormone melatonin, disruption to which
has been implicated in higher breast
cancer risk among night shift workers,
may boost oestrogen production.
Around one in three women in both
groups had worked night shifts. There
was no evidence that those who had
worked nights for up to 14 years or
between 15 and 29 years had any
increased risk of developing breast
cancer.
But those who had worked nights for 30 or
more years were twice as likely to have
developed the disease, after taking
account of potentially influential factors,
although the numbers in this group were
comparatively small.
The associations were similar among
those who worked in healthcare and those
who did not.