Does Melatonin Cause Dementia?

The use of melatonin supplements has spiked significantly in the U.S. in recent years, prompting calls for more research into the effects of long-term melatonin supplementation in humans.

That’s because relatively little research has been done concerning how taking melatonin pills on a regular basis affects overall health. Particularly in aging populations with Alzheimer's or dementia. Melatonin support has also been recommended for those who are blind and struggle with a regular sleep schedule.

Synthetic versions of this hormone are frequently sold over the counter as a sleep aid, and research indicates that it likely impacts various aspects of health and wellness. The limited evidence available is also mixed on whether it benefits people who are struggling with sleep.

A research letter published in JAMA last year drew attention to roughly a five-fold increase in people taking melatonin in the U.S. between 1999 and 2018. The findings by a team of researchers in Beijing and the Mayo Clinic in Rochester, Minnesota cited data from a National Health and Nutrition Examination Survey. They called for more research on this topic in the science community.

Melatonin is a natural hormone that our brains produce, generally increasing when we’re exposed to the dark (at night) and decreasing during daylight. Thus, it plays a dynamic role in regulating sleep and circadian rhythms in humans and other mammals. 

The physiological production of this hormone typically declines in someone as they age, which might impact sleep patterns. That’s where oral supplements of melatonin offer potential promise and have been prescribed to populations with dementia and those struggling with sleep. 

But the precise way that melatonin regulates sleep is not fully understood. For example, in its natural state, it doesn’t have a sedating effect. In fact, in nocturnal animals, the natural chemical is active and associated with wakeful states rather than sleep. 

Beyond sleep, melatonin also has proven to be a potent immunomodulatory hormone and antioxidant, with properties that seem to reduce blood pressure, upregulate bone cell proliferation and inhibit bone resorption, according to a detailed review published early this year in Clinical Interventions in Aging.

Read More: The Importance of Sleep for Your Body

Because of these many functions, and some adverse effects with melatonin in limited trials, that review suggested that “melatonin should thus be considered a medication, albeit a relatively safe one, rather than a harmless dietary supplement.”

The Mayo Clinic deems melatonin supplements as “generally safe” when treated as a sleeping pill and used under a doctor’s supervision. But because the FDA defines the hormone as a dietary supplement, the product gets little oversight and regulation in the U.S., compared to over-the-counter medicine and prescription drugs. 

Read More: Do Melatonin Diffusers Help You Sleep Better — and Are They Safe?

Because both aging and dementia often impact the sleep cycle in aging populations, some have turned to melatonin to help treat symptoms of Alzheimer’s and other fatal neurodegenerative diseases.

In this arena, too, the results are mixed based on limited clinical trials. One of the major dilemmas is assessing the long-term effects and possible risks of taking supplemental melatonin with the potential immediate benefits of managing symptoms, such as insomnia.

“Some studies have found neuroprotective effects of melatonin itself, but there are also concerns over the long-term health consequences of melatonin,” says Yue Leng, an epidemiologist at the University of California San Francisco.

Just this year, Leng published a study that compared the potential risk of dementia associated with various sleep medications based on the race of participants.

That work indicated that frequent use of sleep medications seems to be associated with an increased risk of dementia in white older adults. However, the scope of the research was unable to pinpoint any associations between dementia risk and melatonin specifically, due to the small sample of participants who reported using it. 

“The effects of melatonin use on dementia risk is a controversial topic,” Leng says. “More research is needed to examine both the short-term and long-term effects of melatonin on sleep and cognition in older adults.”

Read More: What You Need to Know About the 6 Stages of Alzheimer’s Disease

Similarly, a 2016 Cochrane review identified a significant lack of evidence and research regarding sleep medication for people with dementia.

Based on limited trials that have been done, the researchers in that review found no evidence that melatonin had a significant impact — adverse or beneficial — to those with dementia. They also found no significantly improved sleep in those who took melatonin. But this was based on limited data, with only four trials at the time involving 222 participants.

That same review found some evidence to support the use of a low dose of trazodone (prescription drug) to treat sleep issues in people with dementia, and no evidence for any effect of the sleeping pill ramelteon (prescription drug) on patients with mild to moderate Alzheimer's dementia. This was also based on limited evidence.

The report ultimately concluded that much more research is needed in this field. “This is an area with a high need for pragmatic trials, particularly of those drugs that are in common clinical use for sleep problems in dementia," the researchers write. "Systematic assessment of adverse effects is essential.”

Read More: The 4 Main Types of Dementia