Non-24 simply means a person’s Circadian Rhythm is not on a 24-hour day. In Sighted Non-24, the Circadian Rhythm is disrupted. Most Non-24 patients are blind, but sighted people can have it, too. In blind people, the lack of light perception throws the Circadian Rhythm out of sync. In sighted people, there is no singular cause and many factors can be at play.