Effects of BL Exposure on Circadian Rhythms and Rhythm-Related Disorders

Circadian rhythms represent a core physiological mechanism sustaining human physiological homeostasis and normal bodily function. Environmental light serves as a primary exogenous zeitgeber for circadian regulation. Among visible light spectral components, BL (BL) exerts a critical modulatory influence on the circadian system, with dual implications for physiological regulation and clinical intervention: excessive or inappropriately timed exposure may lead to circadian disruption, whereas appropriately timed BL interventions show potential to improve circadian alignment in selected populations. Accumulated evidence indicates that circadian disruption is associated with sleep disorders, mood disturbances, neurodegenerative disorders, as well as metabolic and immune dysfunction, and may have bidirectional relationships with disease progression. Nevertheless, most existing studies concentrate on circadian modulation by broad-spectrum light. Few efforts have synthesized the molecular mechanisms, potential disease-related pathways, and targeted intervention frameworks of BL-associated circadian disruption, and the translational potential of BL’s bidirectional effects remains under-summarized, forming a prominent research gap. To fill this gap, this narrative review centers on the “BL-circadian rhythm-disease” regulatory axis. It outlines biological pathways in which circadian disruption may be implicated in multiple neurodegenerative disorders, highlights the circadian-modulating properties of BL, describes evidence linking inappropriate BL exposure to circadian disruption and disease onset or progression, and compiles clinical findings on BL-based interventions and their potential benefits for circadian function and selected disease-related symptoms. However, much of the evidence derives from observational studies and animal experiments, and a causal pathway linking BL exposure to disease through circadian disruption has not been definitively established. This review discusses the potential adverse and beneficial effects of BL in circadian disruption-related pathologies, addresses current research limitations, and offers theoretical references and fresh insights for mechanistic investigations, clinical research, and translational development of BL-targeted interventions.