Why measuring the start of melatonin production in dim light is important before treating sleep timing disorders

Exogenous melatonin is increasingly used in patients with insomnia or circadian rhythm sleep disorders (CRSD).

• Administering melatonin 1-2 hours before bedtime may not always be effective for treating CRSD.
• The timing of melatonin administration should align with individual circadian rhythms, assessed through dim light melatonin onset (DLMO).
• If melatonin is not timed according to a patient's circadian timing, it could be ineffective or lead to adverse effects.
• Endogenous melatonin levels can be reliably measured using saliva collected at home.
• A clinically useful DLMO can be calculated with a fixed threshold.
• Diary and polysomnographic sleep-onset times do not reliably predict DLMO or circadian timing in CRSD patients.

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