Melatonin and the risk of AMD

Pubblicato il

Thursday, 17 October 2024

Argomento

Retina

Melatonin, in addition to helping us sleep better, may be useful in reducing the risk of age-related macular degeneration (AMD), as shown by data reported in the recent study Melatonin and Risk of Age-Related Macular Degeneration

What it is and how it works

Melatonin is a hormone that regulates our sleep and is produced almost exclusively by the pineal gland o epiphysis, an endocrine gland of the brain, belonging to the epithalamus.

Melatonin levels in the blood vary over the course of 24 hours and, in particular, are low during the day, while they start to rise about 1 to 3 hours before the usual bedtime. They remain high for the duration of sleep and decline about an hour before waking up.

Melatonin has multiple functions and is used as a nutritional supplement, both to regularise sleep and to treat other disorders, as it regulates the circadian rhythm, i.e. the mechanism that allows the synchronisation of the light/dark and sleep/wake rhythms.

In practice, the reduction of light stimulation in the evening hours, via particular receptors in the retina, activates the production of melatonin by the pineal gland. Melatonin, in turn, by reducing the level of internal temperature, activates sleep-inducing mechanisms.

All people can be distinguished into two different chronotypes, depending on the time at which melatonin is produced:

people from the serotype, individuals who tend to be very active and perform well in the evening, go to bed late, but then have difficulty waking up early in the morning;
people from the morning chronotype, individuals who experience drowsiness quite early in the evening, but then manage to get up in the early hours of the morning and be more productive in the first part of the day.

Melatonin, through a direct effect via the placenta, influences the early developmental stages of the embryo, glial and neuronal development and may play an ontogenic role in the establishment of the day/night rhythm and in the synchronisation of the foetal biological clock.

Therapeutic uses

Levels of endogenous melatonin, i.e. melatonin produced by the body, decline dramatically with age and this deficiency may be one of the factors behind the reduction in sleep quality and quantity in elderly individuals. Therefore, the use of extended-release melatonin is recognised as a treatment option for insomnia in individuals over the age of 55. Moreover, as melatonin also regulates the time at which the subject falls asleep, its use appears indicated in the subjects with circadian rhythm disorder. A current example is adolescents, who tend to increasingly postpone the time they fall asleep and often find it difficult to wake up in the morning at times compatible with going to school. If this problem becomes chronic and worsens over time, so-called 'phase postponement syndrome' can develop, which can greatly interfere with daytime performance and the subject's ability to wake up and stay awake and alert at school.

Scientific studies have shown that melatonin plays aanti-inflammatory and antioxidant actionso much so that its use was recommended during the Covid19 pandemic to reduce susceptibility or disease severity.

Moreover, again through its anti-inflammatory and neuroprotective action at the level of the central nervous system, it appears that this hormone may have aprotective action against neurodegenerative diseases preventing, in particular, the deposition and accumulation of neurotoxic substances.

Precisely because of these properties, the use of melatonin has recently been recognised as one of the treatments of first choice in children/adolescents with neurodevelopmental disorders, particularly autism.

Melatonin and DMLE

A recent retrospective cohort study tested the hypothesis that melatonin supplementation may help reduce the risk of development and progression of AMD.

The research was conducted on TriNetX, a national database containing anonymised digital medical data of inpatients and outpatients throughout the United States, during the period from December 2023 to March 2024. Participants, aged 50 and over 70 years, were partly without a history of previous AMD and partly with a history of non-exudative (or dry) AMD and were divided into groups based on the use of melatonin supplementation.

The experimental hypothesis that melatonin can counteract or slow down the onset and progression of AMD has been confirmed, although the mechanism by which melatonin performs this protective function of the retina has not been clarified. It has been observed, among other things, that lifestyle may influence this association, which, however, will have to be investigated in further clinical studies.