Women who are ’larks’ have a lower risk of developing breast cancer

Women who are 'larks', functioning better at the beginning of the day than the end of the day, have a lower of risk breast cancer, according to new research led by the University of Bristol presented at the 2018 NCRI Cancer Conference today [Tuesday 6 November]. The study of several hundred thousand women, which was investigating whether the way people sleep can contribute to the development of breast cancer, also found some evidence for a causal link between sleeping for longer and breast cancer. Dr Rebecca Richmond , a research fellow in the Cancer Research UK Integrative Cancer Epidemiology Programme and the MRC Integrative Epidemiology Unit at the University of Bristol and colleagues looked at data from 180,215 women enrolled with the UK Biobank project , and 228,951 women who had been part of a genome-wide association study of breast cancer conducted by the international Breast Cancer Association Consortium (BCAC), which has the largest collection of genetic data on women with breast cancer obtained so far. "Using genetic variants associated with people's preference for morning or evening, sleep duration and insomnia, which had previously been identified by three recent UK Biobank genome-wide association studies, we investigated whether these sleep traits have a causal contribution to the risk of developing breast cancer," she said. The team used a method called 'Mendelian randomisation', which uses genetic variants associated with possible risk factors, such as sleep characteristics, to investigate whether they are involved in causing diseases such as breast cancer.