In a study recently published in The Journals of Gerontology, researchers examined metabolites, small chemicals and molecules created during normal processes in the body. They found that certain combinations of these metabolites were associated with earlier or later death in dogs in ways that closely resembled patterns previously identified in humans.

“The molecules that are risky for dogs or protective against a sooner death are very similar to those in people, showing that we share important features of aging biology, which is really interesting and rewarding,” said Dr. Kate Creevy, chief veterinary officer for the Dog Aging Project and a professor in the Texas A&M College of Veterinary Medicine and Biomedical Sciences, where the work of the Dog Aging Project is generously supported by the WoodNext Foundation. “Our findings also highlight the value of pet dogs as a model for studying long-term health and lifespan.”

Searching for Biological Signs of Lifespan

Metabolites can provide a snapshot of what is happening inside cells, making them useful for detecting biological patterns that may be connected to health and aging.

For the study, researchers analyzed blood samples from dogs participating in the Dog Aging Project. This community science effort follows dogs throughout their lives, with owners contributing detailed survey information and, in some cases, physical samples. The research team examined the blood for metabolic patterns associated with lifespan, focusing specifically on whether individual dogs died earlier or later.

“Death is an easy outcome to understand,” Creevy said. “It is very easy to tell when a person or a dog has died, whereas other features of aging health are a bit more nuanced.”

Using mortality as a clear endpoint allows scientists to work backward and investigate which biological processes may have contributed to the outcome. These processes can include metabolism, inflammation and the ways cells react to stress.

“If we understand why something happened, we have a greater chance of identifying ways to change it,” Creevy said.

A Metabolic Fingerprint of Aging

Rather than focusing on individual molecules, the researchers analyzed thousands of metabolites together to look for larger patterns associated with risk. Creevy said these broader groups can reveal more about what may be taking place inside cells than any single molecule alone.

“Some of my colleagues refer to it as a fingerprint,” Creevy said. “We often look at a pattern or grouping that has a relationship with better or worse outcomes rather than just looking at a single molecule.”

These measurable biological indicators, known as biomarkers, can help researchers estimate the likelihood of certain health outcomes by revealing changes occurring inside the body.

“Importantly, those biomarkers do not necessarily cause an outcome; when we find a biomarker associated with sooner or later mortality, we don’t know that it’s causing it,” Creevy said. “But if we understand why that biomarker is present, we may be able to identify what the cause of the relationship is.”

Finding these recurring patterns gives scientists possible starting points for investigating the mechanisms behind aging and, eventually, identifying biological targets that might help improve health over time.

Dogs and Humans Share Similar Aging Signals

The researchers then asked whether the metabolic patterns seen in dogs also appeared in people. To find out, they compared their results with five large published studies of human mortality that used similar methods to examine metabolites.

Across those studies, the signals associated with earlier or later death were broadly similar to those found in dogs.

That consistency was one of the most striking results, adding evidence that dogs and humans share important features of the biology that underlies aging.

“Frequently, we know a little more about this in people than we do in dogs,” Creevy said. “If we have the same targets, we’ll be able to leverage human research to benefit dogs.”

The similarities could allow scientists to use knowledge already gained from human research to improve canine health, while also using dogs to study how aging develops across an entire lifespan.

Why Dogs Are Valuable for Aging Research

Pet dogs offer several advantages for researchers studying aging. They share many parts of everyday life with humans, including their surroundings, diets and activity patterns. That overlap gives scientists an opportunity to examine how lifestyle and environment affect long-term health.

“One of the things we like most about learning from dogs as it pertains to aging is their widely varied lifestyles that mirror their owners’ lifestyles in a way that’s less true for other companion animals,” Creevy said.

Cats, for example, often live more independent and relatively consistent lifestyles. Dogs are more likely to follow the routines, environments and activity patterns of the people they live with.

Their shorter lifespans provide another major advantage. Humans, on average, live into their 70s, while dogs typically live only 12-13 years. That difference allows researchers to observe aging and lifespan outcomes in dogs much more quickly than would be possible in human studies.

Inside the Dog Aging Project

The research was made possible by the Dog Aging Project, a nationwide, long-term study that follows pet dogs living with owners across the United States.

Owners who participate provide extensive information about their dogs’ lives, while a subset also submit biological samples each year. Together, those contributions allow researchers to track changes in health and aging over time.

“The owners who enroll their dogs make everything possible,” Creevy said. “The dedication and commitment of these owners to participate in research and discovery to better the health of dogs is remarkable.”

Creevy said the latest findings are an early but important step toward understanding the mechanisms that influence aging. Researchers have now identified metabolic patterns associated with lifespan, giving them specific biological signals to investigate further.

“This is a starting point,” she said. “We’ve identified these metabolites, and now we know where to start looking.”

For people who own dogs, Creevy said the practical message is straightforward. Many of the same behaviors that promote healthier aging in people are also likely to benefit dogs.

“Keeping them on a healthy diet, at a healthy body weight, and preserving mobility and cognitive health — just like we would do for ourselves,” Creevy said. “What’s good for us is probably good for them.”

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.

Researchers Looked for Long-Term Heart Risks

Melatonin is often promoted as a safe sleep aid, but researchers say there is limited evidence about its cardiovascular safety when taken for extended periods.

That uncertainty led the team to investigate whether long-term melatonin use might be associated with heart failure among people who already had chronic insomnia.

Heart failure does not mean that the heart has completely stopped working. It develops when the heart cannot pump enough oxygen-rich blood to meet the body’s needs. According to the American Heart Association’s 2025 Heart Disease and Stroke Statistics, the condition affects about 6.7 million adults in the U.S.

Researchers used data from the TriNetX Global Research Network, a large international database containing de-identified electronic health records.

They examined five years of medical records for adults with chronic insomnia whose records showed melatonin use for more than a year. Those participants were matched with other people who also had insomnia but had no documented melatonin use.

Anyone who had already been diagnosed with heart failure or who had been prescribed other sleep medications was excluded.

Heart Failure Risk Was About 90% Higher

The main analysis found a substantial difference between the two groups.

Among adults with insomnia, people with documented long-term melatonin use (12 months or more) had about a 90% higher chance of developing heart failure during the following five years compared with matched nonusers. Heart failure occurred in 4.6% of the melatonin group compared with 2.7% of the comparison group.

Researchers then performed another analysis designed to strengthen confidence that participants had actually been using melatonin over an extended period.

When they limited the analysis to people who had filled at least two melatonin prescriptions at least 90 days apart, the association remained. That group had an 82% higher risk of heart failure. (Melatonin is only available by prescription in the United Kingdom.)

Hospitalization and Death Were Also Higher

A secondary analysis found even larger differences in some outcomes.

People in the melatonin group were nearly 3.5 times as likely to be hospitalized for heart failure as those in the comparison group. The hospitalization rates were 19.0% and 6.6%, respectively.

Deaths from any cause were also more common among people with documented melatonin use. During the five-year period, 7.8% of participants in the melatonin group died compared with 4.3% of those in the non-melatonin group, making the risk nearly twice as high.

“Melatonin supplements are widely thought of as a safe and ‘natural’ option to support better sleep, so it was striking to see such consistent and significant increases in serious health outcomes, even after balancing for many other risk factors,” Nnadi said.

The results also drew concern from sleep researcher Marie-Pierre St-Onge, Ph.D., C.C.S.H., FAHA, who was not involved in the study.

“I’m surprised that physicians would prescribe melatonin for insomnia and have patients use it for more than 365 days, since melatonin, at least in the U.S., is not indicated for the treatment of insomnia. In the U.S., melatonin can be taken as an over-the-counter supplement and people should be aware that it should not be taken chronically without a proper indication,” said Marie-Pierre St-Onge, Ph.D., C.C.S.H., FAHA, chair of the writing group for the American Heart Association’s 2025 scientific statement, Multidimensional Sleep Health: Definitions and Implications for Cardiometabolic Health.

St-Onge is a professor of nutritional medicine in the division of general medicine and director of the Center of Excellence for Sleep & Circadian Research in the department of medicine at Columbia University Irving Medical Center in New York City.

Important Limitations Complicate the Findings

The study comes with several significant limitations, particularly because melatonin is handled differently from one country to another.

Some countries, such as the United Kingdom, require a prescription for melatonin, while others, including the United States, allow people to buy it over the counter. Researchers did not have access to participants’ locations because the medical data had been de-identified.

Melatonin use was identified only when it appeared in electronic medical records. That means people in the U.S. or other countries who bought melatonin over the counter without having it entered into their medical records could have been incorrectly classified as nonusers.

As a result, the melatonin and nonmelatonin groups may not perfectly reflect who was actually taking the supplement.

There was another complication involving hospitalizations. The number of heart failure-related hospitalizations was higher than the number of newly diagnosed heart failure cases because hospitals may enter a variety of related diagnostic codes. Those records do not always include a code specifically identifying a new heart failure diagnosis.

Researchers also did not have information about how severe each participant’s insomnia was or whether participants had other psychiatric disorders.

Those missing factors are important because people with more severe insomnia, depression, anxiety, or other conditions may be more likely to use melatonin and could independently have a different cardiovascular risk.

“Worse insomnia, depression/anxiety, or the use of other sleep-enhancing medicines might be linked to both melatonin use and heart risk,” Nnadi said. “Also, while the association we found raises safety concerns about the widely used supplement, our study cannot prove a direct cause-and-effect relationship. This means more research is needed to test melatonin’s safety for the heart.”

What the Study Included

• The analysis included 130,828 adults (average age of 55.7 years; 61.4% women) who had been diagnosed with insomnia.
• The data came from TriNetX, established in 2013, a growing global network of real-world, de-identified patient information used for medical research.
• Of the participants, 65,414 had been prescribed melatonin at least once and reported using it for at least one year.
• Researchers also created a comparison group (control group) made up of people who had never been prescribed melatonin. These participants were matched to the melatonin group using 40 factors, including demographic characteristics, existing health conditions, and medications.
• Anyone who had already been diagnosed with heart failure was excluded, as were people who had been prescribed other kinds of sleeping pills such as benzodiazepines.
• The melatonin and comparison groups were matched for age, sex, race/ethnicity, heart and nervous system diseases, medications for heart and nervous system diseases, blood pressure, and body mass index.
• Researchers then examined electronic medical records covering the five years after the groups were matched.
• For the primary analysis, they searched for medical codes indicating an initial diagnosis of heart failure. Secondary outcomes included codes associated with hospitalization for heart failure or death.
• The researchers also carried out what is known as a sensitivity analysis, a method used to check whether results remain similar when the study criteria are changed slightly.
• For this additional test, participants in the melatonin group had to have filled at least two melatonin prescriptions at least 90 days apart. The association with higher heart failure risk remained, providing an additional check on the original findings.
• Even so, the researchers emphasize that the study was observational. It identified an association between long-term documented melatonin use and serious health outcomes, but it cannot establish that melatonin directly caused those outcomes. Further research will be needed to determine whether long-term melatonin use itself affects cardiovascular health and, if so, why.

The findings suggest that the region’s geology could eventually support a new domestic energy source and, if developed at scale, a major hydrogen export industry.

Magnetite Could Generate Hydrogen Underground

The research focuses on magnetite, a mineral that is abundant in Western Australia’s huge iron ore deposits across the Pilbara region.

Scientists from ECU’s School of Engineering found that magnetite can release hydrogen gas when it reacts with hot water under conditions similar to those deep below the Earth’s surface.

The team also discovered a way to stimulate the process. By injecting a solution into banded iron formations, the researchers were able to increase hydrogen generation, raising the possibility that naturally produced hydrogen could one day be deliberately enhanced underground.

“Australia could be sitting on a massive, untapped energy reserve — and the potential is enormous,” Associate Professor Alireza Keshavarz said.

“There is enough hydrogen for Australia to benefit for generations, and potentially enough for us to become a major exporter of clean energy to the rest of the world.”

Recreating Deep Underground Conditions

To investigate how the process works, the researchers placed magnetite samples in water at 200°C under high pressure for 60 days. Those conditions were designed to reproduce the hot, pressurized environment found deep underground.

The experiments gave researchers a clearer picture of how natural hydrogen can form within rock and what conditions are needed for production to continue over time.

The findings are especially significant for Western Australia because the region contains some of the largest banded iron formations on Earth.

“Western Australia has some of the world’s largest banded iron formations. If we can unlock this resource at scale, it could be transformative for our energy future,” lead author Kaveh Moghanirahimi said.

“We even see the potential for Western Australia to strengthen its energy independence during times of crisis through access to this naturally generated hydrogen.”

From Laboratory Experiments to Natural Hydrogen Exploration

Professor Stefan Iglauer, from ECU’s School of Engineering, said the results bring researchers closer to understanding how hydrogen production might work in real underground rock formations rather than only in controlled laboratory settings.

“This work helps bridge the gap between laboratory experiments and real geological systems,” Professor Iglauer said.

The study also found that the amount of magnetite alone does not determine how much hydrogen can be produced. The structure of the rock matters as well, particularly whether water can move through it and reach fresh mineral surfaces.

“Our findings show that hydrogen production depends not only on the amount of magnetite present, but also on how easily water can access fresh mineral surfaces through fractures, pores and permeable pathways.”

That means fractures, pores, and other pathways through the rock could play a critical role in determining whether natural hydrogen can be generated efficiently enough to become a practical energy resource.

The research, Geometry-driven controls on hydrothermal natural hydrogen generation from magnetite mineral, has been published in the International Journal of Hydrogen Energy.