Source: http://www.bbc.com/news/magazine-2766139...

There are regular warnings that people aren't sleeping properly. Too much light from electronic devices before bedtime. Not enough time in bed. Excessive caffeine. Now there's another potential worry - too much light in the bedroom.

Previous studies have linked light at night with ill health in rodents. Now a study of 113,000 women suggests that it could cause obesity in humans. The work by Oxford University researchers for the Institute of Cancer Research found that women had larger waistlines if their bedroom was "light enough to see across", the researchers found.

Prof Derk-Jan Dijk, of the Surrey Sleep Centre, said people "should assess their bedroom and see how easy it would be to make it darker". But have our bedrooms got lighter?

There has probably been a trend towards lighter rooms over the past century, says Alex Goddard, curator at London's Geffrye Museum, which is devoted to the history of the home.