The findings were particularly concerning among younger adults. People ages 18 to 34 accounted for a substantial share of the reported heart problems involving caffeinated products, according to independent, preliminary research presented at the American Heart Association’s Scientific Sessions 2026.

Researchers emphasized that the findings do not establish that energy drinks or stimulant supplements caused these medical emergencies. However, the unusually high frequency of certain cardiovascular events in FDA safety reports suggests that these widely available products deserve closer examination.

Growing Concerns About Energy Drinks and Heart Health

The energy drink industry has expanded rapidly, with sales more than doubling over the past decade and exceeding $20 billion in 2024. Despite their popularity, scientists still have limited information about the cardiovascular effects of energy drinks and supplements containing stimulants.

Existing evidence suggests that consuming large amounts of caffeine can harm the cardiovascular system. Medical professionals have also documented cases of arrhythmias (irregular heart rhythms) and sudden cardiac death following the consumption of these products. Some of these incidents involved young adults who had no previously identified risk factors for heart disease.

A 2026 American Heart Association Scientific Statement on caffeine and cardiovascular disease indicates that most adults can generally consume up to 400 mg of caffeine daily without significant safety concerns (the equivalent of up to 5, 8-ounce cups of regular black caffeinated coffee).

However, caffeine concentrations can differ dramatically between products. Certain energy drinks provide up to three times as much caffeine per fluid ounce as brewed coffee, while some pre-workout supplements contain more than 12 times the concentration found in coffee.

Another concern involves how these products are regulated. The U.S. Food and Drug Administration (FDA) classifies energy drinks and stimulant supplements as foods or dietary supplements rather than medications. As a result, they are not subject to the same safety testing requirements that medications must meet before entering the market.

“These products are marketed as everyday pick-me-ups and sold next to soda and bottled water, so most people assume they carry no real risk,” said study author Sai Samayamanthula, a fourth-year medical student at the University of Virginia School of Medicine in Charlottesville, Virginia. “For many healthy people, if these products are consumed occasionally, the risk is probably small. However, individuals who consume energy drinks or other stimulant-containing supplements regularly can quickly exceed the recommended daily limit for caffeine, so it’s important for people to know that there may be a risk of cardiovascular harm with these products.”

FDA Reports Reveal Striking Differences in Cardiac Events

To investigate possible cardiovascular safety concerns, researchers examined a federal database containing reports of suspected adverse reactions to foods and dietary supplements. They compared products containing caffeine and other stimulants with products that did not contain these ingredients.

The comparison group included commonly consumed products such as soft drinks, smoothies, vitamins, protein bars, and meal replacement shakes. Researchers examined reports involving people ages 13 and older submitted between 2017 and 2025.

Several differences stood out in the analysis:

• Cardiac arrest: Reports involving caffeine and stimulant products were approximately 11 times more likely to mention cardiac arrest than reports involving products without these ingredients.
• Heart attacks: Heart attacks appeared about 4.5 times more frequently in reports associated with energy drinks and stimulant supplements.
• Abnormal heart rhythms: Reports involving stimulant products were roughly four times more likely to include ventricular arrhythmias (abnormal rhythm in the heart’s lower pumping chambers) or heart palpitations.
• Other cardiovascular symptoms: The researchers also identified higher reporting frequencies for rapid heart rate (nearly 3 times more often), chest pain (2.71 times more often) and fainting (about 2 times more often).
• Young adults: Approximately 45% of cardiovascular event reports involving caffeine and stimulant products concerned adults between ages 18 and 34.
• Men and women: Comparable patterns appeared in reports submitted for both sexes.

These differences describe how frequently certain medical problems appeared within the FDA reports. They do not mean that people consuming energy drinks face an 11 times greater actual risk of cardiac arrest or a 4.5 times greater risk of having a heart attack.

“Our findings support the case for more systematic safety monitoring of caffeine- and stimulant-containing products. In addition, healthcare professionals should remember to ask their younger patients who have palpitations, chest pain, or fainting spells if they recently or regularly consume these products,” Samayamanthula said.

Why Young Adults May Be Particularly Vulnerable

One of the most notable findings was the large proportion of cardiovascular reports involving younger adults. Researchers have not yet determined why the connection between stimulant products and reported heart problems appeared so frequently in this age group.

Several explanations are possible. Younger consumers may use energy drinks and stimulant supplements more often, increasing the likelihood that these products appear in reports of medical emergencies.

How the products are consumed could also influence the pattern. Potential contributing factors include the circumstances surrounding their use (for example, consuming them before intense exercise or mixing them with alcohol or drugs). Some individuals may also have previously undiagnosed heart conditions that could make them more susceptible to cardiovascular complications.

These possibilities remain uncertain, and additional research will be needed to determine which factors, if any, help explain the unusually high reporting frequency among younger adults.

Do Energy Drinks Actually Cause Heart Attacks?

Although the results raise important questions about products containing concentrated caffeine and other stimulants, experts caution against interpreting the findings as proof of a direct cause.

“This study raises concerns that products with very high amounts of caffeine may be harmful to the cardiovascular system,” said Gregory M. Marcus, M.D., M.A.S., FAHA, chair of the 2026 American Heart Association scientific statement on caffeine and cardiovascular disease. “Although there are biological reasons why that connection could be possible, the study does not prove that caffeine products cause these events, because other factors may have influenced the results found in this analysis. More research is needed to understand whether these stimulant products are truly responsible for the reported heart-related events.”

Marcus did not participate in the research. He is a professor of medicine at the University of California, San Francisco School of Medicine and serves as associate chief of the Cardiology for Research program at the University of California, San Francisco Health.

Because the analysis relied on reports submitted voluntarily to the FDA, it cannot establish whether the products themselves were responsible for the cardiovascular events. Other health conditions, behaviors, or circumstances may have played a role.

How Researchers Analyzed the FDA Safety Reports

The research team reviewed 28,345 reports of possible adverse events submitted to an FDA safety database from 2017 through 2025.

Of these, 854 reports involved energy drinks or dietary supplements containing caffeine or other stimulants. The remaining 27,491 reports concerned products without caffeine or stimulant ingredients and served as the comparison group.

Researchers classified products according to the ingredients they contained. The stimulant category included caffeine, methylxanthines (theobromine, guarana, yerba mate, green tea/coffee extracts) and sympathomimetics (synephrine, yohimbine, ephedra, DMAA, higenamine).

Rather than evaluating individual brands, the researchers grouped products by their ingredients. Consequently, the findings apply to broad categories of caffeinated and stimulant products and do not identify any particular brand as more dangerous than another.

The researchers also highlighted important limitations in the available data. Reports were voluntarily submitted by members of the public, consumers, healthcare professionals, and manufacturers, meaning that the database does not provide a complete record of everyone who experienced a possible adverse reaction.

Just as importantly, the researchers could not determine how many people consumed these products without developing cardiovascular problems. They also could not establish how many people experienced heart problems but never submitted a report.

Without those figures, the analysis cannot calculate the actual likelihood of a heart attack, cardiac arrest, or another cardiovascular event among consumers of energy drinks and stimulant supplements.

Nevertheless, the findings reveal a potentially important safety signal. Researchers say more systematic monitoring and further studies are needed to determine whether these products contribute directly to serious heart problems, particularly among younger adults who frequently consume them.

The 2026 Antarctic ozone hole ranked as the seventh-largest in 48 years of observations, based on its average seasonal area. Scientists attributed the expansion primarily to an exceptionally strong polar vortex, a large circulation of winds that influences atmospheric conditions over Antarctica. They also emphasized that international efforts to reduce harmful chemicals have prevented the hole from becoming even larger.

Between September 7 and October 13, 2026, when ozone depletion was at its seasonal peak, the hole covered an average of approximately 9.6 million square miles (25 million square kilometers). That is more than twice the size of the United States. Scientists closely monitor ozone in the stratosphere because it serves as Earth’s natural “sunscreen,” protecting living organisms from dangerous solar radiation. Unlike this beneficial layer high in the atmosphere, ozone near Earth’s surface is a pollutant frequently associated with human activities.

Antarctica’s Ozone Hole Reaches Its Largest Size in a Decade

The ozone hole reached its maximum extent on September 18, spreading across 10.5 million square miles (27.1 million square kilometers). This was approximately 90% of the size of the largest ozone hole ever measured, which occurred on September 9, 2000.

“The annual ozone hole has been forming later in the season in recent years, which tells us the ozone layer is healing,” said Paul Newman, a senior scientist at the University of Maryland and longtime leader of NASA’s ozone research team at the agency’s Goddard Space Flight Center. “But an unusually powerful polar vortex has extended ozone depletion in the Antarctic this season, allowing the hole to grow to proportions we haven’t seen in a decade.”

Although the hole expanded to an extraordinary size, the results also demonstrate the benefits of decades of international environmental protections. Without reductions in chemicals known to destroy ozone, the affected area could have been substantially greater.

“The 2026 ozone hole is large but could have been 1 to 2 million square miles (3.5 million square kilometers) larger if ozone-depleting substances were as prevalent in the atmosphere today as they were at their year 2000 peak,” Newman said.

How a Powerful Polar Vortex Accelerates Ozone Loss

Ozone depletion begins with chemicals released through human activities, particularly compounds containing chlorine and bromine. Atmospheric circulation transports these substances into the stratosphere, where ultraviolet radiation breaks them apart. The released chlorine and bromine atoms then participate in chemical reactions involving particles in Antarctic stratospheric clouds, leading to the destruction of ozone.

A major factor in this process is the stratospheric polar vortex, a seasonal band of strong winds that circles Antarctica. This circulation traps extremely cold air over the region, allowing the formation of the special clouds that help trigger ozone destruction. When the vortex becomes unusually strong or expansive, conditions favorable for ozone loss can persist across a larger area.

In 2026, atmospheric disturbances that would normally weaken the vortex were unusually subdued. This allowed the circulation to remain powerful and helped create a broader region where ozone could be destroyed.

“The polar vortex was unusually large this year in part because planetary-scale weather systems that typically well up from the lower atmosphere and break up the vortex were especially weak in August and September,” said Amy Butler, a research scientist at the NOAA Chemical Sciences Laboratory. “That weak wave action kept the strongest polar vortex winds further from the South Pole by several degrees of latitude, creating a larger area for conditions ideal for ozone depletion to occur.”

NASA and NOAA Measure the 2026 Ozone Hole

Despite its exceptional geographic size, the 2026 ozone hole did not experience the same extreme levels of ozone loss observed during record-breaking events 10 or 20 years earlier.

To measure ozone concentrations, NOAA researchers launched instruments attached to weather balloons from the South Pole Baseline Atmospheric Observatory. They also collected readings using the Dobson Ozone Spectrophotometer, an optical device designed to measure atmospheric ozone. Their observations showed that ozone levels directly above the South Pole fell to their lowest reading of 2026 on October 17, reaching 105 Dobson units.

The Dobson unit is the standard measurement used to describe the total amount of ozone above a particular location. To illustrate the scale, 100 Dobson units would produce a layer of ozone just 1 millimeter thick, approximately the thickness of a dime, if all the ozone in the atmospheric column were compressed to standard temperature and pressure at sea level. The lowest ozone concentration ever measured over the South Pole was 92 Dobson units in October 2006.

Satellites provide another essential source of information. Since 1979, spaceborne instruments have helped scientists observe changes in the ozone layer and track its condition over time. The 2026 measurements included data from NASA’s Aura satellite, NOAA-20, NOAA-21, and the Suomi National Polar-orbiting Partnership satellite, a joint NASA and NOAA mission.

Why Earth’s Ozone Layer Is Still Recovering

Scientists say the latest observations reinforce evidence that international restrictions on ozone-destroying chemicals are working. Much of that progress can be traced to the Montreal Protocol, a global agreement adopted in 1987 to phase out substances responsible for damaging the ozone layer.

Under the agreement, countries committed to replacing harmful compounds such as chlorofluorocarbons with alternatives that pose less danger to atmospheric ozone. According to Stephen Montzka, a senior scientist at NOAA’s Global Monitoring Laboratory, chlorine concentrations in the Antarctic stratosphere associated with ozone-depleting chemicals have declined by approximately one-third compared with their peak levels in the 1980s.

These reductions are significant because chlorofluorocarbons and other ozone-depleting compounds were once common in refrigerators, air conditioning systems, building insulation, and other everyday products. Although many of these substances have been phased out, they can remain in the atmosphere for decades. Additional emissions can also occur when older equipment, materials, and landfill waste release chemicals that were manufactured years ago.

Because these compounds break down so slowly, repairing the ozone layer takes many decades. Nevertheless, continued monitoring by NASA and NOAA indicates that the long-term recovery is progressing. Even with unusually large seasonal ozone holes such as the one observed in 2026, scientists expect the Antarctic ozone hole to recover by the 2070s.

The latest findings illustrate how exceptional atmospheric conditions can temporarily produce severe ozone depletion without reversing decades of environmental progress. They also highlight the lasting impact of international cooperation in protecting Earth’s atmosphere.

The discovery, published in the journal Cell, raises an extraordinary possibility. The cave could represent the earliest known burial location reserved for one sex by a human relative other than Homo sapiens.

Homo naledi lived approximately 335,000 to 241,000 years ago and has fascinated scientists since its discovery in 2013. This extinct species combined primitive features resembling those of apes with other characteristics more closely associated with modern humans.

A Strange Mystery Hidden in Ancient Human Fossils

One of the biggest puzzles surrounding Homo naledi involves the remarkably similar appearance of adult fossils recovered from the cave’s Dinaledi Chamber. For more than a decade, researchers have struggled to explain why these individuals showed so little of the physical variation normally associated with differences between males and females.

To investigate, an international research team involving the University of York, the University of Copenhagen, and more than 10 other institutions turned to proteins preserved in the ancient remains.

The scientists used a technique involving gentle acid etching to recover tiny protein fragments known as peptides from fossilized tooth enamel. This approach allowed them to collect samples while minimizing damage to the valuable fossils. In total, they examined 23 teeth belonging to at least 20 different individuals.

The researchers specifically searched for Amelogenin-Y, a protein produced from a gene on the male Y chromosome. Surprisingly, they found no evidence of this male-specific marker.

To verify that their findings were reliable, specialists at the University of York’s chemistry facility examined the amino acids in the samples. Their analysis confirmed that the proteins were genuinely ancient rather than the result of contamination from modern sources.

Could Homo naledi Have Had an All-Female Burial Site?

Dr. Marc Dickinson, from the University of York’s Department of Chemistry, said: “The lack of male markers with the group is truly fascinating. It is incredibly exciting to gain a window not only into the biology of our ancestors, but also into how they lived.

“These findings offer rare insights into a culture that has, until now, been difficult to access directly. Advances in ancient protein analysis are opening the door to a far richer and more nuanced understanding of ancient hominins.”

The results raise important questions about how Homo naledi individuals lived, organized their communities, and treated their dead. If the Dinaledi Chamber was intentionally used only for females, it could point to surprisingly elaborate social customs among these ancient human relatives.

Such a practice might even suggest symbolic burial traditions once believed to be exclusive to Homo sapiens, or modern humans.

However, the researchers emphasize that an all-female burial site is not the only possible interpretation of the evidence.

Another explanation involves the genetics of Homo naledi itself. If the population lived in extreme isolation, the gene responsible for producing Amelogenin-Y could have undergone a mutation or disappeared entirely.

Under that scenario, some of the individuals could actually have been male, even though their teeth did not contain the protein normally used to identify them.

Ancient Tooth Enamel Opens a New Window Into Human Evolution

The ability to recover proteins from fossils this old is particularly valuable because tooth enamel can protect biological material for extraordinarily long periods.

Palesa Madupe, who carried out the research during her postdoctoral work at the University of Copenhagen, explained why teeth offer such an important source of evidence.

“Unlike those found in other remains like bone fragments, proteins in tooth enamel are preserved because dental enamel — the hardest tissue in the human body — shields proteins from environmental contamination even for millions of years.

“This makes them ideal carriers of genetic information from deep time. Our study helps in the long-standing mystery of why Homo naledi lacked significant variation; it’s probably because they could have all belonged to one sex.”

The research represents the largest collection of individuals from an extinct hominin species ever examined using ancient protein analysis.

Whether the fossils belong entirely to females or include males with an unusual genetic signature, the discovery provides an important new perspective on Homo naledi. It also demonstrates how proteins preserved in ancient teeth can reveal clues about extinct human relatives that their bones alone cannot provide.

As researchers continue investigating the mystery, the findings could reshape our understanding of the social lives and possible burial traditions of ancient human species.