Melatonin may stave off age-related vision loss, study hints

Melatonin supplements may reduce the risk of developing age-related macular degeneration (AMD), the most common cause of severe vision loss in people over age 50. 

Researchers uncovered this link after analyzing electronic medical records gathered between 2008 and 2023 from patients in the U.S. 

The scientists examined records from more than 238,000 people over age 50 who had no history of AMD, about 121,000 of whom reported taking melatonin. From this data, the scientists estimated that the individuals taking melatonin were 58% less likely to go on to be diagnosed with AMD within the 15-year study period than those who were not. 

The former group had to have reported to their doctor that they were taking melatonin at least four times within the 15-year window, with a minimum three-month gap between these reports. In the U.S., melatonin is considered to be a dietary supplement, so it can be purchased without a prescription. 

Related: Kids' use of melatonin 'exceedingly common,' Colorado study finds

Although it revealed an interesting link, the study has some major caveats. 

Notably, over-the-counter melatonin supplements can vary considerably in terms of their purity and the concentration of ingredients included. Studies have suggested that melatonin gummies sold in the U.S. often contain much higher doses than listed — or more rarely, they contain no melatonin at all. This means that the actual dose of melatonin that people were taking in this study is unknown. 

But even so, the research, published June 6 in the journal JAMA Ophthalmology, hints that melatonin could potentially help ward off a very common form of vision loss. 

"I think the potential of this low cost, widely available supplement in reducing the risk AMD is potentially exciting," Dr. Glenn Yiu, a professor of ophthalmology at University of California, Davis Health who was not involved in the research, told Live Science in an email. With the current study's caveats in mind, "I will be interested to see if other more rigorous studies confirm these interesting findings," he added.

Melatonin and vision loss

In the human eye, the retina contains light-sensitive cells that send messages to the brain. The macula, the central part of the retina, enables us to see objects that are directly in front of us. AMD affects eyesight because it progressively damages the macula. People with AMD can experience blurred or distorted vision in the center of their visual field, but the disease doesn't cause total blindness. 

Two major types of AMD exist: dry AMD and wet AMD. Dry AMD is the milder form of the disease that occurs in 80% of cases, and it's caused by the gradual breakdown of light-sensitive cells in the macula. Wet AMD additionally involves the abnormal growth of blood vessels under the retina, and these blood vessels can begin to leak fluid, damaging cells and leading to severe vision loss. Between 10% and 15% of patients with dry AMD will go on to develop wet AMD. 

In addition to looking at people without AMD who later developed the disease, the researchers wanted to see if taking melatonin could prevent the progression from dry to wet. So, in a second analysis, the team probed the medical records of about 128,000 patients who had been diagnosed with dry AMD, roughly 66,000 of whom were taking melatonin and 62,000 were not. They found that those who were taking melatonin were 56% less likely to go on to develop wet AMD in a 15-year time frame than those who weren't. 

In both analyses, similar patterns were seen among patients in their 50s, 60s and 70s, the team found. 

Because the study looked at only associations between melatonin and AMD, it cannot prove that melatonin directly counters the biological processes behind the condition. The authors also acknowledge that people's lifestyle habits and health care access may have influenced their risk of AMD, rather than melatonin, but they didn't consider these factors. 

The findings do reaffirm earlier research in rodents and humans that suggest melatonin, which is often prescribed to treat sleep disorders such as insomnia, may be able to target some of the key biological processes that underlie AMD. This includes heightened inflammation and oxidative stress, or a build-up of free radicals in the body that can damage cells. This is important considering that there is currently no cure for AMD, and preventive interventions are often limited to lifestyle modifications, such as maintaining a healthy diet and quitting smoking. 

"The potential benefits of new treatments to prevent AMD are enormous from a public health perspective," David Rein, a senior fellow in public health at the National Opinion Research Center (NORC) at the University of Chicago, who was not involved in the research, told Live Science in an email. 

Gold-standard clinical trials are still needed to determine whether melatonin actually prevents the development or progression of AMD. These trials would compare people who take melatonin to those who don't, and the doses and quality of the supplements would be carefully controlled. 

It's important that these trials be completed before doctors make any recommendations about patients using melatonin for eye health, Dr. Rajendra Apte, a professor of opthalamology and visual sciences at Washington University in St. Louis, who was not involved in the research, told Live Science in an email. 

This article is for informational purposes only and is not meant to offer medical advice.

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