DENVER – Exposure to bright light has already been established as effective therapy for depression. Now it is also showing promise for improving daytime sleepiness and mood in nondepressed older individuals with primary insomnia.
The evidence comes from a study of 51 patients with primary insomnia–that is, no other psychiatric or medical explanations for their sleeplessness. The patients were randomized to 12 weeks of daily bright light or dim light therapy at home.
The daily treatment sessions involved 45 minutes of reading at a distance of 18 inches from a desk lamp equipped with either a 10,000-lux bulb or a less-than-50-lux bulb.
Participants averaged 64 years of age, were not taking hypnotic medications, and received sleep hygiene instruction as part of the study, Leah Friedman, Ph.D., explained at the annual meeting of the Associated Professional Sleep Societies.
Daytime mood and sleepiness improved to a significantly greater extent during the 12 weeks of bright light exposure, compared with dim light exposure.
Paradoxically, these benefits were achieved despite little or no change in objectively measured sleep variables. For example, total sleep time as measured by wrist actigraphy for 7 days at baseline and again at the end of the 12-week study actually decreased in both treatment groups.
“That's not what you'd want to see,” observed Dr. Friedman, a senior research scholar at Stanford (Calif.) University.
However, the preliminary analysis of sleep diary data has been more promising. Patients reported that they felt their sleep got better with bright light exposure, even though actigraphy didn't reflect this, she continued.
The worse a patient's daytime sleepiness and dysphoria at baseline, the more likely the patient was to respond favorably to bright light therapy.
The study was supported by the Veterans Affairs Palo Alto Health Care System.