To the Editor:
We read with great interest the recent article by Zhou et al. [1]. They demonstrate, through systematic review and metanalysis, the patients with short sleep duration (<6 h) are at an elevated risk of Age-related Macular Degeneration (AMD). We would like to extend this discussion and encourage conversation around the hypothesis that the association between AMD and sleep disruption may, in some instances, occur in conjunction with underlying neurodegenerative disease (NDD).
The relationship between sleep and AMD appears to be one of significance in patients afflicted with sleep-depriving illness. The majority of the literature refers to sleep and AMD relationship in the presence of a sleep-limiting disease, such as sleep apnoea or insomnia. Further, the observation that correction of the sleep-wake cycle with prescription melatonin truncates AMD progression would support sleep’s direct pathophysiological influence in AMD [2].
Sleep is also intrinsically involved in the pathogenesis of NDD. Sleep disturbances in Alzheimer’s disease involve the disruption of the sleep-wake circadian cycle, with changes in the neuroendocrine mediators; orexin and melatonin [3]. There is also a decrease in rapid eye movement (REM) and Non-REM sleep, with increases in nocturnal awakenings [3]. Similarly, sleep disturbances are observed in synucleinopathies, Parkinson’s disease (insomnia, parasomnia and nocturnal awakenings), dementia with Lewy bodies (REM sleep behaviour disorder) and multiple system atrophy (REM sleep behaviour disorder, insomnia, central sleep apnoea) [3].
AMD may be associated with NDD and, in some instances, is believed to develop prior to cognitive decline. In particular, the cardinal pathophysiologic process of Alzheimer’s disease, may promote retinal pigment epithelial dysfunction, typical of AMD [4]. This pathophysiological mechanism is further supported with clinical data. For example, Shang et al. demonstrated that mong participants with AMD at baseline, 2.94 cases per 1000 person-years developed all-cause dementia compared with 1.78 of those without AMD [5].
The complex, interdependent relationship between sleep, AMD and NDD requires further examination. The impetus for such examination is not only driven by the significant burden of these disorders, but also the potential for pathophysiological insights. We would be interested in the authors’ opinions on the possible interrelatedness of AMD, sleep dysfunction, and NDD.
Author contributions
BS, JGK, SB and WC contributed to the conceptualisation, writing, and revision of the manuscript.
Funding
This research received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.
Competing interests
The authors declare no competing interests.
Footnotes
Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
References
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