Green Light Not Effective for Delayed Sleep-Wake Phase Disorder

By Will Boggs MD

NEW YORK—Green-bright-light therapy is no better than red light for treating adolescents and young adults with delayed sleep-wake phase disorder (DSWPD), researchers from Australia report.

Whether morning activity could improve outcomes remains unclear, they report in Sleep Medicine, online February 9.

"It was most surprising to find that there were no differences in treatment based on whether green or red light was administered in bright-light therapy,” said Dr. Cele Richardson from Flinders University, in Adelaide.

“There is convincing experimental evidence to suggest that short-wavelength light (e.g., blue-green light) is most effective at shifting circadian rhythms earlier, with relatively little phase shifting occurring in response to long-wavelength light (e.g., red),” she told Reuters Health by email.

DSWPD presents as an inability to initiate sleep at a desired clock time along with difficulty waking to fulfill morning requirements. Weak evidence supports the use of strategically timed melatonin or combining post-awakening light and prescribed sleep-wake scheduling.

Dr. Richardson and colleagues compared the efficacy of green light to red light, with or without morning physical activity, in 60 adolescents and young adults with DSWPD. Their mean age was 16 years (range, 13 to 24).

Despite efforts to have one group engage in physical activity and the other to be sedentary in the morning, there were no between-groups differences for self-reported daily activity in the morning or overall, suggesting that the experimental manipulation did not lead to a meaningful increase in physical activity.

All groups demonstrated significant improvements for all study variables except bedtime and wake after sleep onset (WASO), with no difference between the green- and red-light groups, with or without morning activity.

Patients maintained these improvements at the three-month follow-up; 38% of all participants requested further treatment.

“Despite the lack of differences between green- and red-light therapy, our study adds to evidence supporting the use of bright-light therapy for the treatment of DSWPD in adolescents and young adults,” Dr. Richardson said.

“As per clinical guidelines, ‘bright-light therapy’ in our study included psychoeducation, scheduled sleep times which became gradually earlier, evening light restriction in the two hours before bed, and exposure to bright light for 30-60 minutes immediately after awakening, all of which were covered in weekly sessions with a sleep psychologist,” she said. “All of these components no doubt contributed to the efficacy of treatment, so I would urge physicians to include each of these components when treating young people with DSWPD.”

“Overall, these results suggest we need to refine our understanding of how bright-light therapy improves sleep for adolescents with DSWPD; that is, what is the mechanism for improvement?” Dr. Richardson said.

Dr. Katerina Danielsson from Uppsala University in Sweden, who has studied various aspects of DSWPD but was not involved in the new work, told Reuters Health by email, "The most interesting finding was that all groups improved their sleep. This finding highlights the importance of regular wake-up times for DSWPD patients."

SOURCE: https://bit.ly/2GXoa8k

Sleep Med 2018.

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