A new study just published a few days ago in the journal named JAMA Ophthalmology tried to assess whether melatonin can confer any sort of benefit against age-related macular degeneration (AMD).
What is AMD?
AMD is the leading cause of irreversible vision loss in the elderly. It is predicted to affect as many as 288 million people by 2040. It affects the retina of patients, in a region named macula, which has a rich concentration of light sensitive cells. As the name suggests, it is a disease that is associated with age. It is a multifactorial disease, meaning that multiple factors contribute to it, from our own genetic information (or our blueprint if you must) to environmental influences (dietary patterns, other diseases, smoking and UV exposure, etc). Due to its commonality, and the major economic, social and human burden it represents, it has been studied in detail for many decades. Amongst the main avenues of research are what its pathogenesis is, or what pathologic abnormalities take place for the disease to show up and progress.
AMD has two forms, named dry and wet. The wet form of AMD has a quite effective treatment with a class of medication called anti-angiogenic drugs, which have modified the outcomes of the condition. This is not the case though of the late form of dry AMD, where our measures or interventions are mainly preventive and limited to lifestyle modifications. We have a full Podcast episode on AMD, so feel free to check it out as we have detailed the condition there.
What about melatonin?
Melatonin is a hormone that we have in our bodies, which essentially signalise to the brain that is time to rest. At night time, our levels of this hormone rise, staying high up until daytime. Melatonin is also made in laboratories, with a synthetic version of it being available to increase our natural supply of this hormone. It is used mainly to regulate night and day (or sleep-awake) cycles. So, it is frequently prescribed for patients facing sleep problems like insomnia. And can also be used to treat symptoms relating to jet lag after long flights.
But then the question is: why look at associations between melatonin and AMD? Well, the reason for that is due to potential anti-inflammatory and anti-oxidant properties that were seen in both animals and humans, which are amongst the main avenues of treatments of new drugs being tested for the disease.
Study design and findings
Back to the study in question – this was a retrospective cohort study looking at many millions of US patients, with the final analysis including a whooping 121,523 individuals. The authors evaluated the relative risk – a statistical tool design to establish the risk of an event in the exposure group compared to the non-exposure group – in patients with no history of AMD and in patients with a diagnosis of AMD.
The results supported a protective association of melatonin and AMD. Specifically, melatonin was associated with a reduced risk of developing AMD, as well as a reduced risk of AMD progression compared to the control cohort. Very cool!
This was a study with a strong methodology, and the authors did use quite adequate statistical tools. There are some limitations though, mostly related to the fact that AMD is, as we discussed above, a multifactorial disease. So, it may as well be that there are some confounding factors there, such as lifestyle modifications. Smoking, for instance, has been strongly associated with AMD – if there were more patients smoking in the group that were melatonin-naive, this could potentially put a bit of bias in this interpretation, given they would already be at a higher risk of developing AMD due to the sole fact that they smoke. But this is not to take away at this study as these findings were remarkable, and provide “big data” evidence that further research needs to take place to elucidate the role of melatonin as a therapy to reduce the risks of AMD.
I will see you later!
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Thales A. C. de Guimaraes, MD, PhD
Host and Founder | Eyes On Research