Blue-light blocking glasses as adjunctive treatment reduce depressive symptoms and sleep latency in older adults: a pilot exploratory study

Late-life depression is frequently associated with circadian dysregulation and impaired sleep initiation, even under ongoing pharmacological treatment[1] . Age-related alterations in retinal photoreception, reduced amplitude of circadian rhythms, and diminished melatonin secretion may further increase vulnerability to sleep disturbance and mood instability in older adults[2] . Short-wavelength light exposure in the evening suppresses pineal melatonin secretion via retinal projections to the suprachiasmatic nucleus[3] , potentially disrupting circadian synchronisation and downstream affective regulation. Adjunctive strategies targeting evening photic input may therefore modulate melatonergic signalling and complement conventional antidepressant approaches[4] . However, clinical evidence supporting this mechanism in institutionalised older adults remains limited.

This pilot exploratory study aimed to evaluate whether adjunctive evening short-wavelength light attenuation using blue-light blocking glasses is associated with changes in depressive symptoms and sleep latency in older adults residing in long-term care facilities.

Twenty adults aged ≥65 years residing in long-term care facilities in Lisbon, Portugal, with clinically relevant depressive symptoms were enrolled in a six-week single-arm study. Cognitive impairment was excluded (mean Mini-Mental State Examination 26.9 ± 2.1). Participants continued their usual clinical care and wore blue-light blocking glasses each evening for six weeks, targeting circadian photic input pathways. Depressive symptoms were assessed using the 15-item Geriatric Depression Scale. Sleep latency was derived from the Pittsburgh Sleep Quality Index. For paired comparisons between baseline and week 6, normality of difference scores was assessed using the Shapiro–Wilk test. Paired t-tests were applied when differences were normally distributed; otherwise, Wilcoxon signed-rank tests were used. Effect sizes were calculated using Cohen’s d (paired) or r, as appropriate.

Depressive symptoms significantly decreased over the intervention period. Mean Geriatric Depression Scale scores improved from 8.0 ± 2.4 at baseline to 4.3 ± 2.7 at week 6 (mean change −3.7 ± 1.8). Difference scores did not deviate from normality (Shapiro–Wilk p = 0.385), and paired t-testing confirmed a significant reduction (p < 0.001) with a large effect size (Cohen’s d = 2.04).

Sleep latency also decreased significantly. Mean sleep latency was reduced from 39.0 ± 41.7 minutes at baseline to 27.0 ± 29.8 minutes at week 6 (mean change −12.0 ± 14.9 minutes). Difference scores were non-normally distributed (Shapiro–Wilk p < 0.001), and Wilcoxon signed-rank testing indicated a significant reduction (p < 0.001) with a large effect size (r = 0.76).

These preliminary findings suggest that adjunctive attenuation of evening short-wavelength light exposure may modulate circadian regulation and be associated with clinically meaningful reductions in depressive symptoms and improvements in sleep initiation in institutionalised older adults. The parallel improvement in mood and sleep latency is consistent with a circadian-mediated mechanism involving melatonergic signalling. Nevertheless, the uncontrolled and exploratory design limits causal interpretation. Randomised controlled trials incorporating objective circadian biomarkers are warranted to clarify therapeutic potential and underlying neurobiological mechanisms.

References

1. Amidfar M, Garcez ML, Kim Y-K. The shared molecular mechanisms underlying aging of the brain, major depressive disorder, and Alzheimer’s disease: The role of circadian rhythm disturbances. Prog Neuro-Psychopharmacol Biol Psychiatry [Internet]. 2023;123:110721. https://doi.org/10.1016/j.pnpbp.2023.110721
2. Hood S, Amir S. The aging clock: circadian rhythms and later life. J Clin Investig. 2017;127:437–46. https://doi.org/10.1172/jci90328
3. Brainard GC, Hanifin JP, Greeson JM, Byrne B, Glickman G, Gerner E, et al. Action Spectrum for Melatonin Regulation in Humans: Evidence for a Novel Circadian Photoreceptor. J Neurosci. 2001;21:6405–12. https://doi.org/10.1523/jneurosci.21-16-06405.2001
4. Esaki Y, Kitajima T, Takeuchi I, Tsuboi S, Furukawa O, Moriwaki M, et al. Effect of blue-blocking glasses in major depressive disorder with sleep onset insomnia: A randomized, double-blind, placebo-controlled study. Chronobiol Int. 2017;34:753–61. https://doi.org/10.1080/07420528.2017.1318893