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Sleep Med Rev. 2014 Aug;18(4):333-9. doi: 10.1016/j.smrv.2013.12.001. Epub 2013 Dec 10.

Why the dim light melatonin onset (DLMO) should be measured before treatment of patients with circadian rhythm sleep disorders.

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Department of Clinical Chemistry and Hematology, Rijnstate Hospital, Arnhem, The Netherlands; Governor Kremers Centre, University Maastricht, The Netherlands. Electronic address:
Governor Kremers Centre, University Maastricht, The Netherlands; Centre for Sleep-Wake Disturbances and Chronobiology, Gelderse Vallei Hospital, Ede, The Netherlands.
Division of Sleep Medicine, Brigham & Women's Hospital and Harvard Medical School, Boston, MA, USA.
Governor Kremers Centre, University Maastricht, The Netherlands; Department of Clinical Genetics, Maastricht University Medical Centre, Maastricht, The Netherlands.


Treatment of circadian rhythm sleep disorders (CRSD) may include light therapy, chronotherapy and melatonin. Exogenous melatonin is increasingly being used in patients with insomnia or CRSD. Although pharmacopoeias and the European food safety authority (EFSA) recommend administering melatonin 1-2 h before desired bedtime, several studies have shown that melatonin is not always effective if administered according to that recommendation. Crucial for optimal treatment of CRSD, melatonin and other treatments should be administered at a time related to individual circadian timing (typically assessed using the dim light melatonin onset (DLMO)). If not administered according to the individual patient's circadian timing, melatonin and other treatments may not only be ineffective, they may even result in contrary effects. Endogenous melatonin levels can be measured reliably in saliva collected at the patient's home. A clinically reliably DLMO can be calculated using a fixed threshold. Diary and polysomnographic sleep-onset time do not reliably predict DLMO or circadian timing in patients with CRSD. Knowing the patient's individual circadian timing by assessing DLMO can improve diagnosis and treatment of CRSD with melatonin as well as other therapies such as light or chronotherapy, and optimizing treatment timing will shorten the time required to achieve results.


Circadian rhythm sleep disorders (CRDS); Circadian rhythms; Dim light melatonin onset (DLMO); Melatonin; Sleep; Sleep timing disorders

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