Study: Women early risers may have lower breast cancer risk
By: Team Ifairer | Posted: 14-07-2020
Heart It
Women who like to wake up early every day may be less likely to develop breast cancer than women who prefer to sleep in, a recent study suggests. While previous studies have linked inconsistent sleep schedules and getting too much rest to an increased risk of breast cancer, researchers haven't looked as often at how much women's wake-up time might impact this risk, researchers note in the BMJ.
For the current analysis, researchers analyzed genetic variants associated with three sleep traits: sleep duration, insomnia, and a so-called morning or evening chronotype, referring to early or late risers. They looked at data on 180,216 women in the UK Biobank study and 228,951 women in the Breast Cancer Association Consortium (BCAC) study.
In the UK Biobank study, among every 100 women who were early risers, there was one fewer case of breast cancer than among every 100 women who were late risers. But there wasn't a clear connection between breast cancer and sleep duration or insomnia.
In the BCAC group, women who woke up early also had a lower risk of breast cancer. In this study, sleeping more than the recommended 7 to 8 hours a night was associated an increased risk - 19% for every extra hour.
"The findings of a protective effect of morning preference on breast cancer risk in our study are consistent with previous research highlighting a role for night shift work in the development of breast cancer," said Rebecca Richmond, lead study author and a researcher at the University of Bristol in the UK.
"One particular mechanism which might explain the link, known as the
`light-at-night' hypothesis, involves the suppression of melatonin
levels in women exposed to the artificial night at a light, which in
turn influences various hormonal pathways which might increase risk of
breast cancer," Richmond said by email. But women shouldn't rush to
reset their alarm clocks to lower their breast cancer risk, Richmond
said.
"Our main findings were based on women's reported morning
or evening preference, rather than actually whether they get up earlier
or later in the day," Richmond noted.
Another drawback is that
participants were all of the European ancestry, and results might differ
for women from other racial and ethnic groups.