You may have heard that bright lighting in the evenings can disrupt your sleep. But it turns out some of us are more sensitive to this effect than others. A new study suggests people’s threshold for their body clock hormones being disturbed by late-night light can vary by more than fifty-fold.

“For some people, a dim reading light might as well be daylight, and for others it might as well be darkness,” says Sean Cain at Monash University …