Circadian Rhythm Disorders
One fourth of all chronic sleep disorders are the result of a mismatch between the body’s internal clock and the external 24-hour schedule. These sleep-timing problems are called circadian rhythm sleep disorders because ‘circadian’ describes the body’s daily sleep/wake hormone regulation (Circadian is Latin for ‘about a day’). In addition, most other sleep disorders can damage circadian rhythms and further compound the sleep problem. The National Institute of Health estimates that over 35 million Americans suffer from circadian rhythm disorders.