Melatonin in the afternoons of a gradually advancing sleep schedule enhances the circadian rhythm phase advance.
Study Goal
The researchers aimed to examine the effects of melatonin on circadian rhythm phase advances, sleepiness, and performance compared to placebo when combined with a gradually advancing sleep schedule.
Results Summary
Melatonin produced significantly larger phase advances (1.3 ± 0.7 h) than placebo (0.7 ± 0.7 h) but caused increased sleepiness and performance decrements between ingestion and bedtime. The study concluded that while melatonin enhances phase advances, morning bright light and possibly a lower melatonin dose may be preferable due to side effects.
Population
Twelve adults (five female) aged 20-45 years (mean ± SD = 28.3 ± 7.3 years).
Effective Dosage
3 mg of melatonin taken 11 h before baseline sleep midpoint on the first treatment day and 1 h earlier each subsequent day.
Duration
Three consecutive days of treatment following nine days of fixed 8-h sleep schedules.
Interactions
None mentioned
| Intervention | Direction | Endpoint | Population | Dosage | Impact | Claim # |
|---|---|---|---|---|---|---|
afternoon/evening melatonin (3 mg) | increase | phase advances | twelve adults (five female individuals) aged 20-45 years | 1.3 ± 0.7 h | produced significantly larger advances | #1 |
placebo | increase | phase advances | twelve adults (five female individuals) aged 20-45 years | 0.7 ± 0.7 h | produced advances | #2 |
melatonin | increase | sleepiness | twelve adults (five female individuals) aged 20-45 years | - | caused | #3 |
melatonin | decrease | performance decrements | twelve adults (five female individuals) aged 20-45 years | - | caused | #4 |
adding afternoon/evening melatonin to the gradually advancing sleep schedule | increase | the phase advance | - | - | increased | #5 |
RATIONALE: We test methods to advance (shift earlier) circadian rhythms without producing misalignment between rhythms and sleep. We previously tested (1) a gradually advancing sleep/dark schedule plus morning bright light and afternoon/evening melatonin and (2) the same sleep schedule with only morning bright light. Now we report on the same sleep schedule with only afternoon/evening melatonin. OBJECTIVES: This study aims to examine phase advances, sleepiness, and performance in response to melatonin compared to placebo. METHODS: Twelve adults (five female individuals) aged 20-45 years (mean ± SD = 28.3 ± 7.3 years) completed this within-subjects placebo-controlled counterbalanced study. The participants slept on fixed 8-h sleep schedules for nine days. Then, sleep/dark was advanced by 1 h/day for three consecutive days of treatment. The participants took 3 mg of melatonin or placebo 11 h before baseline sleep midpoint (the optimal time to produce phase advances) on the first treatment day and 1 h earlier on each subsequent day. We measured the dim light melatonin onset before and after treatment. The participants rated subjective symptoms throughout the study. They completed the Psychomotor Vigilance Task and rated sleepiness from 1 h before pill ingestion until bedtime on each treatment day. RESULTS: Melatonin produced significantly larger advances (1.3 ± 0.7 h) compared to placebo (0.7 ± 0.7 h); however, in the hours between melatonin ingestion and bed, melatonin caused sleepiness and performance decrements. CONCLUSIONS: Adding afternoon/evening melatonin to the gradually advancing sleep schedule increased the phase advance, but given the side effects, like sleepiness, it is better to use morning bright light and perhaps a lower dose of melatonin.