Following only two nights of bright light therapy exposure, individuals with early-morning awakening insomnia experience significantly improved sleep patterns and indicators of daytime functioning that last for up to a month after therapy, according to a study in the May 1 issue of the journal Sleep.
The study results show that four hours of bright light therapy for two consecutive nights produce a two-hour delay of the circadian phases of body temperature and melatonin rhythm in otherwise healthy adults with early-morning awakening insomnia.
Over a four-week follow-up period, these individuals show a greater reduction of time awake after falling asleep, a trend toward waking up later in the morning, and a greater total sleep time, as compared with a control group that received only dim red-light exposure.
Leon Lack, Ph.D., of Flinders University in Adelaide, Australia, and colleagues found that those undergoing bright light therapy also show greater improvements in daytime functioning, including fewer days of feeling depressed.
“What was particularly pleasing about our results, in addition to the delay in rhythms produced by the evening bright light, was the improvement in sleep,” says Dr. Lack. “It allowed participants to sleep later in the morning and thus longer in total time. This was also associated with improvement in daytime functioning and feelings.”
People with early-morning awakening insomnia consistently complain of waking up too early in the morning and being unable to go back to sleep, according to background information in the article. The prevalence of this problem tends to increase with age and is associated with a decreased total sleep time and excessive daytime sleepiness.
According to the authors, in a previous study they found that participants with early-morning awakening insomnia reach their minimum body temperature at an average time of 12:20 a.m., more than three hours earlier than a control group. Their average melatonin onset also occurs more than two hours earlier than the control group at 8:30 p.m. This results in an early average wake-up time of 4:49 a.m.
Analysis of the bright-light group during the follow-up period shows a steady phase advance back toward the original timing of their circadian rhythms. Despite this, the members of the bright-light group continue to show positive improvements in their sleep over this period.
The authors suggest that the initial success experienced by these subjects immediately after treatment may have had a positive psychological effect that enabled the participants to maintain their improvements in sleep even when their bodies began to return to old circadian patterns.
Due to the gradual post-treatment return to previous circadian timing, the authors recommend the use of occasional treatment nights of bright-light therapy. They also suggest that further research is needed to determine if this kind of ongoing treatment can maintain the gains that they observed from only two nights of therapy.
According to Dr. Lack, this study also holds promise for people with sleep-onset insomnia who fall asleep much later than normal.
“Sleep-onset insomnia should be treatable, with morning bright light therapy having the effect of shifting circadian timing earlier,” says Dr. Lack. “We are in the process of testing this hypothesis.”
The study group consisted of 24 healthy adults, ages 36 - 68 years, with early-morning awakening insomnia of at least six months duration. Thirteen subjects received 2500 lux of bright-light therapy from 8 p.m. until midnight on the first night, and from 9 p.m. to 1 a.m. on the second night. Eleven members of the control group received less than 100 lux of dim red light during the same times.
Core body temperature and melatonin production were measured during 26-hour wakeful routines before and after the two nights of light therapy. Sleep diaries, activity monitors, urine samples, and daytime functioning questionnaires were also used as assessment tools during the follow-up period.
The journal Sleep is the official publication of the Associated Professional Sleep Societies, LLC, a joint venture of the American Academy of Sleep Medicine and the Sleep Research Society. It is a peer-reviewed research and clinical journal addressing sleep, circadian rhythms, and the diagnosis and treatment of the broad spectrum of sleep disorders.