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Chronobiol Int. 2020 Feb;37(2):248-259. doi: 10.1080/07420528.2019.1692859. Epub 2019 Nov 22.

Block the light and sleep well: Evening blue light filtration as a part of cognitive behavioral therapy for insomnia.

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Sleep Medicine and Chronobiology, National Institute of Mental Health, Klecany, Czech Republic.
Third Faculty of Medicine, Charles University in Prague, Prague, Czech Republic.


The objective of the present study was to assess the effect of combining CBT-I with wearing blue-light blocking glasses 90 min prior to bedtime on subjective and objective sleep parameters and daily symptoms (anxiety, depression, hyperarousal). Thirty patients (mean age 48.1 ± 16.13 years, range 21-71, 15 men/15 women) completed a CBT-I group therapy program, with groups randomly assigned to either "active" (blue-light filtering glasses) condition or "placebo" (glasses without filtering properties) condition. Patients were continually monitored by wristwatch actigraphy, kept their sleep diaries and completed a standard questionnaire battery at admission and after the end of the program. Statistical analyses showed a greater reduction of BAI score in "active" (4.33 ± 4.58) versus "placebo" (-0.92 ± 3.68) groups of patients [F = 6.389, p = .019, Cohen's d = 1.26] and significant prolongation of subjective total sleep time in "active" (-36.88 ± 48.68 min.) versus "placebo" (7.04 ± 47.50 min.) [F = 8.56, p < .01, d = 0.91] group. When pre- and post-treatment results were compared in both groups separately, using paired-samples t-tests, significant differences were observed also in the active group for BDI-II score (t = 3.66, p = .003, Cohen's d = 0.95) and HAS score (t = 2.90, p = .012, Cohen's d = 0.75). No significant differences were found in the placebo group. In active group, there was also a significant reduction of subjective sleep latency (t = 2.65, p = .021, d = 0.73) and an increase of subjective total sleep time (t = -2.73, p = .018, d = -0.76) without change in objective sleep duration which was significantly shortened in the placebo group. We provide further evidence that blocking short-wavelength light in the evening hours may be beneficial for patients suffering from insomnia.


CBT-I; anxiety; blue-light blocking; chronotherapy; depression; insomnia; sleep

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