Phase-shifting effects of bright morning light as treatment for delayed sleep phase syndrome
Bright light has recently been shown to have phase-shifting effects on human circadian rhythms. In this study we applied this effect to 20 patients with delayed sleep phase syndrome (DSPS) who were unable to fall asleep at conventional clock times and had a problem staying alert in the morning. In a controlled treatment study, we found that 2 h of bright light exposure in the morning together with light restriction in the evening successfully phase advanced circadian rhythms of core body temperature and multiple sleep latencies in these patients. This finding corroborates the importance of light for entraining human circadian rhythms.
The effect of evening bright light in delaying the circadian rhythms and lengthening the sleep of early morning awakening insomniacs.
Past studies have predicted that early morning awakening insomnia is associated with early circadian rhythms, meaning that your body temperature drops way before your bedtime.
Because bright light stimulation in the evening is said to delay the phase of circadian rhythms, we tested it on nine early morning awakening insomniacs.
Sleep was evaluated with wrist motion sensors and their temperature and melatonin level graph were measured as well.
In the initial evaluation, the temperature rhythm phase positions of these insomniacs did appear to be earlier than normal. The subjects were then exposed to bright light stimulation (2,500 lux) from 8 pm to midnight on two consecutive evenings.
Following the evening bright light treatment, temperature rhythm phase markers were delayed 2-4 hours and melatonin phase markers were delayed 1-2 hours. Sleep onset times were not changed but the mean final wake-up time was delayed from 5 am hours to 6 am, resulting in a mean increase of total sleep time of about one hour.
This pilot study suggests that evening bright light treatment may be an effective nondrug treatment for early morning awakening insomnia.