Researchers emphasize that the study was observational - correlation is not the same as causation
American Heart Association
Long-term use of melatonin, a widely used sleep supplement, was linked to a higher risk of heart failure, hospitalization for heart failure, and death from any cause among people with chronic insomnia, according to preliminary research presented at the American Heart Association's Scientific Sessions 2025.
The findings do not prove that melatonin itself caused the
increased risks. However, they raise new questions about the long-term safety
of a supplement that many people view as a harmless or "natural" way
to improve sleep.
Why Melatonin Is So Widely Used
Melatonin is a hormone made naturally by the pineal gland in
the brain. It helps control the body's sleep and wake cycle, also known as the
circadian rhythm. Levels of the hormone typically rise when it gets dark and
fall during daylight.
Synthetic melatonin is chemically identical to the hormone
produced by the body. It is commonly used for insomnia (difficulty falling
and/or staying asleep) and jet lag.
Melatonin supplements are available over the counter in many
countries, including the U.S. In the U.S., over-the-counter supplements are not
regulated, so each brand of supplement can vary in strength, purity, etc.
For the new study, researchers divided participants
according to their documented melatonin use. People with at least one year of
melatonin use recorded in their electronic medical records were placed in the
"melatonin group." Those with no record of melatonin use anywhere in
their medical records were assigned to the "non-melatonin group."
"Melatonin supplements may not be as harmless as
commonly assumed. If our study is confirmed, this could affect how doctors
counsel patients about sleep aids," said Ekenedilichukwu Nnadi, M.D., lead
author of the study and chief resident in internal medicine at SUNY
Downstate/Kings County Primary Care in Brooklyn, New York.
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