Abstract
Delayed sleep phase disorder (DSPD) is a circadian rhythm disorder characterized by a stable 24 h sleep pattern but with sleep times that are significantly delayed with respect to conventional or desired sleep–wake times [1]. Prevalence of DSPD in the community can be up to 10% [2] and it is commonly misdiagnosed as insomnia and depression. Two of the treatment options for DSPD include morning bright light and evening melatonin [1], however, currently there are no studies assessing the clinical effectiveness of combined use of these treatments for DSPD.
We reviewed clinical records of a consecutive series of 28 patients (median age 22 (range 15–60) years), who received bright light and melatonin for DSPD in an insomnia clinic in Auckland. Diagnosis of DSPD was by clinical assessment and a two-week sleep diary. Patients were treated with 3 mg oral melatonin 2 h before desired sleep onset time, and bright light using either a light box (5000 lux) or sun exposure, for at least 30 min between 06.00 and 08.00. Follow-up was carried out either by filling a questionnaire or interview. Primary outcome was patients' reported change in sleep pattern. Median follow-up was 6.4 (range 4-76) weeks. The pre-treatment and with-treatment mean mid sleep phase was calculated using Excel 2007(Microsoft corporation, Redmond, WA).
A total of 23 patients (82%) reported improvement in sleep patterns, while five (18%) reported no change. Symptoms recurred in one patient (4.3%) after two weeks. The mean mid sleep phase significantly advanced from a pre-treatment time of 06.28 (95% CI: 05.44–07.13) to 04.06 (95% CI: 03:05–05.08) with treatment. Two patients (7%) experienced adverse effects of drowsiness and headaches. Five patients (18%) had trouble using the light box consistently and one patient (4%) reported poor adherence to melatonin.
The results indicate that combined bright light and melatonin treatment in the current setting is effective for DSPD. This is consistent with Revell et al. [3] who found that combined bright light and melatonin significantly advanced circadian phase compared to bright light alone in normal subjects. Some randomized controlled trials assessing the effectiveness of either bright light [4] or melatonin [5] compared to placebo for DSPD have reported no statistically significant change in patients' reported sleep symptoms even though circadian phase is advanced in patients. However, results from this case series indicate that the use of combined bright light and melatonin can have additive effects for improving subjective sleep times in DSPD patients, which is consistent with the current understanding of human circadian rhythm [1,5].
The shortcomings of this case series (retrospective design, short follow-up times and the lack of objective assessment of sleeping patterns) hinder the ability to make strong conclusions. However, laboratory assessments for circadian phase markers or performing polysomnography in DSPD patients are impractical in a clinic setting in New Zealand due to cost and lack of resources.
In conclusion, this case series shows that combined bright light and melatonin treatment appears to improve symptoms of DSPD and provides a simple and cost-effective method of treating this common sleep disorder. Further research using this combined treatment approach for DSPD is recommended.