Women who wake up early may have a lower risk of developing breast cancer than the females sleeping for longer hours, a study has found.
Using a technique called Mendelian randomisation, researchers analysed genetic variants associated with three particular sleep traits – morning or evening preference (chronotype), sleep duration, and insomnia.
They analysed databases of more than four lakh women from two studies – UK Biobank study and Breast Cancer Association Consortium (BCAC) study.
After analysing UK Biobank data, the researchers concluded that morning preference was associated with a slightly lower risk of breast cancer than evening preference, whereas there was little evidence for an association with sleep duration and insomnia symptoms.
Analysis from BCAC also supported a protective effect of morning preference, and showed a potential harmful effect of longer sleep duration (more than the recommended 7-8 hours) on breast cancer, whereas evidence for insomnia symptoms was inconsistent.
Eva Schernhammer from the University of Vienna in Austria said these findings, published in the journal BMJ, identify a need for future research exploring how the stresses on our biological clock can be reduced.