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James Michael Stringham, Nicole Tressa Stringham; Short-term macular carotenoid supplementation improves overall sleep quality. Invest. Ophthalmol. Vis. Sci. 2016;57(12):5034.
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The non-image forming photopigment melanopsin is found in intrinsically photosensitive retinal ganglion cells (ipRGCs), where it has been shown to play a role in circadian rhythm entrainment, presumably by detecting the presence of sunlight. Macular pigment (MP) is derived via diet, composed specifically of the carotenoids lutein, zeaxanthin, and mesozeaxanthin, and is concentrated in the central retina. Because MP and melanopsin both preferentially absorb short-wave light, our research sought to address the question of whether increasing participants’ MP optical density (MPOD), via macular carotenoid supplementation for 3 months, would affect sleep quality.
This was a 3-month, double-blind, placebo-controlled trial in which 45 young (aged 18-25 yrs.), healthy individuals participated. Random assignment was used to determine the active supplement group (n = 30) and placebo group (n = 15). Those in the active supplement group ingested daily a pill containing 22mg lutein and 5 mg zeaxanthin isomers, whereas participants in the placebo group took an inert pill. Sleep quality was evaluated with the Pittsburgh Sleep Quality index (PSQI). MPOD was measured with heterochromatic flicker photometry. Measures were conducted at baseline and 3 months; Pearson correlations were used to determine relationships between variables at baseline, and paired-samples t-tests were employed to evaluate changes in both sleep quality and MPOD over the 3-month study period.
At baseline, sleep quality and MPOD were not found to be significantly related (r = 0.112; p = 0.46). For the 3-month intervention, the experimental group exhibited significant improvements in overall sleep quality (t = 2.95; p = 0.0063) and MPOD (t = -5.19; p < 0.001). The placebo group did not change for either of these variables over the study period (p > 0.50 for both).
It is perhaps the case that increases in MPOD serve to absorb more short-wave (blue) light from sources (such as computer screens, tablets, or smartphones) that can be used during nighttime hours, and would otherwise provide a circadian signal to stay awake. Although the lack of a significant correlation between MPOD and sleep quality at baseline is not consistent with this conclusion, it may be that acute, relatively rapid increases in MPOD are not immediately compensated for by the ipRGC circadian rhythm system, and therefore manifest as improvements in sleep quality.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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