Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Non 24 hour sleep wake disorder ?
    ### Response:
    Non 24 hour sleep wake disorder refers to a steady pattern of one- to two-hour delays in sleep onset and wake times in people with normal living conditions. This occurs because the period of the person's sleep-wake cycle is longer than 24 hours. The condition most commonly affects people who are blind, due to an impaired sense of light-dark cycles.
    