Myopia, or near-sightedness, is associated with delayed melatonin circadian timing and lower melatonin output in young adult humans.
Study objectives
Myopia, or near-sightedness, is the most common refractive vision disorder and predisposes the eye to many blinding conditions in adulthood. Recent research has suggested that myopia is associated with increased endogenous melatonin ( mélatonine )production. Here we investigated the differences in melatonin ( mélatonine )circadian timing and output in young adult myopes and non-myopes (or emmetropes) as a pathogenesis for myopia.
Methods
A total of 18 myopic (refractive error [mean ± standard deviation] −4.89 ± 2.16 dioptres) and 14 emmetropic participants (−0.09 ± 0.13 dioptres), aged 22.06 ± 2.35 years were recruited. Circadian timing was assessed using salivary dim light melatonin ( mélatonine )onset (DLMO), collected half-hourly for 7 h, beginning 5 h before and finishing 2 h after individual average sleep onset in a sleep laboratory. Total melatonin ( mélatonine )production was assessed via aMT6s levels from urine voids collected from 06:00 pm and until wake-up time the following morning. Objective measures of sleep timing were acquired a week prior to the sleep laboratory visit using an actigraphy device.
Results
Myopes (22:19 ± 1.8 h) exhibited a DLMO phase-delay of 1 hr 12 min compared with emmetropes (21:07 ± 1.4 h), p = 0.026, d = 0.73. Urinary aMT6s melatonin ( mélatonine )levels were significantly lower among myopes (29.17 ± 18.67) than emmetropes (42.51 ± 23.97, p = 0.04, d = 0.63). Myopes also had a significant delay in sleep onset, greater sleep onset latency, shorter sleep duration, and more evening-type diurnal preference than emmetropes (all p < 0.05).
Conclusions
These findings suggest a potential association between circadian rhythms and myopia in humans.
Sleep, Volume 44, Issue 3, March 2021, zsaa208, https://doi.org/10.1093/sleep/zsaa208
Published: 08 October 2020
Source: https://academic.oup.com/sleep/article-abstract/44/3/zsaa208/5919543
