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
Last updated: 6/3/2014
Is non 24 hour sleep wake disorder genetic in sighted people with this disorder?
Non 24 hour sleep wake disorder is not known to be
inherited, and we were unable to find case reports of this condition
clustering in a family. There have been a few studies to see if changes in the MTNR1A and MTNR1B genes affect disease risk. Findings were inconclusive, however one person with non 24 hour sleep wake disorder was found to carry a gene change in both of these genes.
Last updated: 6/3/2014
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Uchiyama M et al. Larger phase angle between sleep propensity and melatonin rhythms in sighted humans with non-24-hour sleep-wake syndrome. Sleep. 2002 Feb 1; 25(1):83-8. http://www.ncbi.nlm.nih.gov/pubmed/11833864. Accessed 6/3/2014.
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