Question: What is (are) Non 24 hour sleep wake disorder ?
Answer: 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. Non 24 hour sleep wake disorder can also affect sighted people. The cause of the disorder in these cases is incompletely understood, but studies suggest melatonin levels play a role.
Source: GARD

Question: What are the symptoms of Non 24 hour sleep wake disorder ?
Answer: What are the signs and symptoms of Non 24 hour sleep wake disorder? The Human Phenotype Ontology provides the following list of signs and symptoms for Non 24 hour sleep wake disorder. If the information is available, the table below includes how often the symptom is seen in people with this condition. You can use the MedlinePlus Medical Dictionary to look up the definitions for these medical terms. Signs and Symptoms Approximate number of patients (when available) Insomnia 90% Visual impairment 90% Anorexia 50% Incoordination 50% Memory impairment 50% The Human Phenotype Ontology (HPO) has collected information on how often a sign or symptom occurs in a condition. Much of this information comes from Orphanet, a European rare disease database. The frequency of a sign or symptom is usually listed as a rough estimate of the percentage of patients who have that feature. The frequency may also be listed as a fraction. The first number of the fraction is how many people had the symptom, and the second number is the total number of people who were examined in one study. For example, a frequency of 25/25 means that in a study of 25 people all patients were found to have that symptom. Because these frequencies are based on a specific study, the fractions may be different if another group of patients are examined. Sometimes, no information on frequency is available. In these cases, the sign or symptom may be rare or common.
Source: GARD