Phase-shifting effects of bright morning light as treatment for delayed sleep phase syndrome.
Level 2 - randomized trial
Controlled trial (indexed as randomized controlled trial) evaluating bright light treatment in 20 patients.
What was done
Twenty patients with delayed sleep phase syndrome who were unable to fall asleep at conventional times and struggled with morning alertness participated in a controlled treatment study. The intervention consisted of two hours of bright light exposure in the morning combined with light restriction in the evening. Circadian phase shifts were evaluated using core body temperature rhythms and multiple sleep latencies.
What was found
Morning bright light combined with evening light restriction successfully phase advanced the circadian rhythms of core body temperature and multiple sleep latencies. The abstract reports no numerical data, effect sizes, or statistical values.
Why it matters
This trial demonstrates that timed morning bright light exposure combined with evening light restriction can phase advance human circadian rhythms to treat delayed sleep phase syndrome.
Limits
The sample size is small with only 20 participants. The abstract does not specify the control condition, light intensity parameters, quantitative outcomes, or long-term clinical persistence of the phase advance.
Cited by
- supports Viewing morning sunlight sets the human circadian rhythm.