Capturing the circadian rhythms of free-running blind people with 0.5 mg melatonin.
Level 4 - case-series / case-control
Small prospective case series / uncontrolled within-subject experimental study
PubMed 11684046 · doi:10.1016/s0006-8993(01)02964-x
What was done
Three totally blind individuals with free-running circadian rhythms (periods >24 h), who had previously responded to melatonin entrainment, were released into a free-run following treatment withdrawal. They were then administered a starting (de novo) nightly dose of 0.5 mg melatonin to determine if this low dose could capture and synchronize their rhythms.
What was found
All three subjects (100%) successfully entrained to the de novo 0.5 mg nightly melatonin dose within a few weeks. The abstract reports no further numerical measurements or physiological values.
Why it matters
This demonstrates that low-dose (0.5 mg) melatonin can initiate circadian entrainment in free-running blind individuals without needing prior high-dose loading.
Limits
The sample size is extremely small (n = 3) with no control group or placebo comparison. The subjects were pre-selected responders who had previously entrained to melatonin, introducing selection bias. The abstract does not report specific circadian phase markers, exact time-to-entrainment figures, or long-term outcomes.
Cited by
- supports Administering a 0.3 to 0.5 mg dose of melatonin in the evening entrains the circadian clock in blind individuals with non-24-hour circadian rhythm disorder.