A new study from the Institute of Cancer Research has found that women will put on more weight if their bedroom is “light enough to see across” while they are sleeping.
Researchers asked 113,000 women to rate the amount of light in their bedrooms and compared this to the participants’ BMI, waist circumference and waist-to-hip ratio.
“Metabolism is affected by cyclical rhythms within the body that relate to sleeping, waking and light exposure,” Professor Anthony Swerdlow, Professor of Epidemiology at The Institute of Cancer Research, London, and co-leader of the study, said.
“The associations we saw in our study between light exposure at night and obesity are very intriguing. We cannot yet tell at this stage what the reason for the associations is, but the results open up an interesting direction for research.“
Dr Matthew Lam, Senior Research Officer at Breakthrough Breast Cancer, added that “These findings add weight to previous results from animal studies that looked into how light exposure, circadian rhythms and metabolism could all be connected in some way.
"It’s too early to suggest that sleeping in the dark will help prevent obesity, a known risk factor for breast cancer, but the association is certainly interesting."
No harm will arise, however, from trying to make bedrooms darker while sleeping, by turning off alarm clocks and standby bulbs that light up parts of a room.
"People in general are not aware of the light present in their bedroom,” Derk-Jan Dijk, a professor at the Surrey Sleep Centre, told the BBC. “I think people should assess their bedroom and see how easy it would be to make it darker."
The research project was funded by Breakthrough Breast Cancer and The Institute of Cancer Research (ICR), with additional support from the NIHR Biomedical Research Centre at The Royal Marsden NHS Foundation Trust and the ICR. The women were selected as part of the Breakthrough Generations Study, following more than 110,000 women in the UK for 40 years, in a bid to find the root causes of breast cancer.