Purpose: Intrinsically photosensitive retinal ganglion cells (ipRGCs) respond to short-wavelength light and contribute to circadian rhythm entrainment. Evening light exposure and/or changes in sleep/wake behavior can cause dysregulation of melatonin, which is associated with impaired mood and cognitive performance. This study examined the effects of modifying short-wavelength blue light exposure on evening melatonin levels, sleep onset, mood and cognition.
Methods: A randomized controlled trial with crossover-design evaluated BluTech Lenses (blue light filter intervention) versus clear lenses with anti-reflective coating only (control). These lenses were fitted into spectacle frames with black-out side-shields worn after 6:00pm for five days (Mon.-Fri.) by 24 undergraduate students. Actigraphy watches non-invasively recorded sleep patterns each night. On the fifth evening, saliva samples were collected to quantify melatonin levels, and self-reported mood and neurobehavioral performance were assessed with the NIH Toolbox Emotion and Cognition batteries, respectively.
Results: A significant increase in melatonin levels was measured with the BluTech Lenses compared to control (9.6 vs. 4.9; p = 0.036). Sleep onset latency measured by actigraphy was slightly reduced with the Blutech Lenses, but not statistically significantly different between glasses. Pattern comparison was significantly improved after wearing the BluTech Lenses (p = 0.03), while other aspects of cognition were not significantly affected (p > 0.05). Perceived hostility was significantly reduced with the BluTech Lenses (p = 0.03); however, other measures of mood were not significantly different between glasses (p > 0.05).
Conclusion(s): BluTech Lenses appear to help regulate melatonin and can potentially be applied to at risk populations (e.g. shift-workers or students who spend nighttime hours studying with electronic devices) in order to lessen the deleterious effects of light exposure at night.