Eunyoung Choi, University of Southern California

What if extreme heat not only leaves you feeling exhausted but actually makes you age faster?

Scientists already know that extreme heat increases the risk of heat stroke, cardiovascular disease, kidney dysfunction and even death. I see these effects often in my work as a researcher studying how environmental stressors influence the aging process. But until now, little research has explored how heat affects biological aging: the gradual deterioration of cells and tissues that increases the risk of age-related diseases.

New research my team and I published in the journal Science Advances suggests that long-term exposure to extreme heat may speed up biological aging at the molecular level, raising concerns about the long-term health risks posed by a warming climate.

Extreme heat’s hidden toll on the body

My colleagues and I examined blood samples from over 3,600 older adults across the United States. We measured their biological age using epigenetic clocks, which capture DNA modification patterns – methylation – that change with age.

DNA methylation refers to chemical modifications to DNA that act like switches to turn genes on and off. Environmental factors can influence these switches and change how genes function, affecting aging and disease risk over time. Measuring these changes through epigenetic clocks can strongly predict age-related disease risk and lifespan.

Research in animal models has shown that extreme heat can trigger what’s known as a maladaptive epigenetic memory, or lasting changes in DNA methylation patterns. Studies indicate that a single episode of extreme heat stress can cause long-term shifts in DNA methylation across different tissue types in mice. To test the effects of heat stress on people, we linked epigenetic clock data to climate records to assess whether people living in hotter environments exhibited faster biological aging.

We found that older adults residing in areas with frequent very hot days showed significantly faster epigenetic aging compared with those living in cooler regions. For example, participants living in locations with at least 140 extreme heat days per year – classified as days when the heat index exceeded 90 degrees Fahrenheit (32.33 degrees Celcius) – experienced up to 14 months of additional biological aging compared with those in areas with fewer than 10 such days annually.

This link between biological age and extreme heat remained even after accounting for a wide range of individual and community factors such as physical activity levels and socioeconomic status. This means that even among people with similar lifestyles, those living in hotter environments may still be aging faster at the biological level.

Even more surprising was the magnitude of the effect – extreme heat has a comparable impact on speeding up aging as smoking and heavy alcohol consumption. This suggests that heat exposure may be silently accelerating aging, at a level on par with other major known environmental and lifestyle stressors.

Long-term public health consequences

While our study sheds light on the connection between heat and biological aging, many unanswered questions remain. It’s important to clarify that our findings don’t mean every additional year in extreme heat translates directly to 14 extra months of biological aging. Instead, our research reflects population-level differences between groups based on their local heat exposure. In other words, we took a snapshot of whole populations at a moment in time; it wasn’t designed to look at effects on individual people.

Our study also doesn’t fully capture all the ways people might protect themselves from extreme heat. Factors such as access to air conditioning, time spent outdoors and occupational exposure all play a role in shaping personal heat exposure and its effects. Some individuals may be more resilient, while others may face greater risks due to preexisting health conditions or socioeconomic barriers. This is an area where more research is needed.

What is clear, however, is that extreme heat is more than just an immediate health hazard – it may be silently accelerating the aging process, with long-term consequences for public health.

Older adults are especially vulnerable because aging reduces the body’s ability to regulate temperature effectively. Many older individuals also take medications such as beta-blockers and diuretics that can impair their heat tolerance, making it even harder for their bodies to cope with high temperatures. So even moderately hot days, such as those reaching 80 degrees Fahrenheit (26.67 degrees Celcius), can pose health risks for older adults.

As the U.S. population rapidly ages and climate change intensifies heat waves worldwide, I believe simply telling people to move to cooler regions isn’t realistic. Developing age-appropriate solutions that allow older adults to safely remain in their communities and protect the most vulnerable populations could help address the hidden yet significant effects of extreme heat.

Eunyoung Choi, Postdoctoral Associate in Gerontology, University of Southern California

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Ashutosh Mangalam, University of Iowa

Multiple sclerosis is a disease that results when the immune system mistakenly attacks the brain and spinal cord. It affects nearly one million people in the U.S. and over 2.8 million worldwide. While genetics play a role in the risk of developing multiple sclerosis, environmental factors such as diet, infectious disease and gut health are major contributors.

The environment plays a key role in determining who develops multiple sclerosis, and this is evident from twin studies. Among identical twins who share 100% of their genes, one twin has a roughly 25% chance of developing MS if the other twin has the disease. For fraternal twins who share 50% of their genes, this rate drops to around 2%.

Scientists have long suspected that gut bacteria may influence a person’s risk of developing multiple sclerosis. But studies so far have had inconsistent findings.

To address these inconsistencies, my colleagues and I used what researchers call a bedside-to-bench-to-bedside approach: starting with samples from patients with multiple sclerosis, conducting lab experiments on these samples, then confirming our findings in patients.

In our newly published research, we found that the ratio of two bacteria in the gut can predict multiple sclerosis severity in patients, highlighting the importance of the microbiome and gut health in this disease.

Bedside to bench

First, we analyzed the chemical and bacterial gut composition of patients with multiple sclerosis, confirming that they had gut inflammation and different types of gut bacteria compared with people without multiple sclerosis.

Specifically, we showed that a group of bacteria called Blautia was more common in multiple sclerosis patients, while Prevotella, a bacterial species consistently linked to a healthy gut, was found in lower amounts.

In a separate experiment in mice, we observed that the balance between two gut bacteria, Bifidobacterium and Akkermansia, was critical in distinguishing mice with or without multiple sclerosis-like disease. Mice with multiple sclerosis-like symptoms had increased levels of Akkermansia and decreased levels of Bifidobacterium in their stool or gut lining.

Bench to bedside

To explore this further, we treated mice with antibiotics to remove all their gut bacteria. Then, we gave either Blautia, which was higher in multiple sclerosis patients; Prevotella, which was more common in healthy patients; or a control bacteria, Phocaeicola, which is found in patients with and without multiple sclerosis. We found that mice with Blautia developed more gut inflammation and worse multiple sclerosis-like symptoms.

Even before symptoms appeared, these mice had low levels of Bifidobacterium and high levels of Akkermansia. This suggested that an imbalance between these two bacteria might not just be a sign of disease, but could actually predict how severe it will be.

We then examined whether this same imbalance appeared in people. We measured the ratio of Bifidobacterium adolescentis and Akkermansia muciniphila in samples from multiple sclerosis patients in Iowa and participants in a study spanning the U.S., Latin America and Europe.

Our findings were consistent: Patients with multiple sclerosis had a lower ratio of Bifidobacterium to Akkermansia. This imbalance was not only linked to having multiple sclerosis but also with worse disability, making it a stronger predictor of disease severity than any single type of bacteria alone.

How ‘good’ bacteria can become harmful

One of the most interesting findings from our study was that normally beneficial bacteria can turn harmful in multiple sclerosis. Akkermansia is usually considered a helpful bacterium, but it became problematic in patients with multiple sclerosis.

A previous study in mice showed a similar pattern: Mice with severe disease had a lower Bifidobacterium-to-Akkermansia ratio. In that study, mice fed a diet rich in phytoestrogens – chemicals structurally similar to human estrogen that need to be broken down by bacteria for beneficial health effects – developed milder disease than those on a diet without phytoestrogens. Previously we have shown that people with multiple sclerosis lack gut bacteria that can metabolize phytoestrogen.

Although the precise mechanisms behind the link between the Bifidobacterium-to- Akkermansia ratio and multiple sclerosis is unknown, researchers have a theory. Both types of bacteria consume mucin, a substance that protects the gut lining. However, Bifidobacterium both eats and produces mucin, while Akkermansia only consumes it. When Bifidobacterium levels drop, such as during inflammation, Akkermansia overconsumes mucin and weakens the gut lining. This process can trigger more inflammation and potentially contribute to the progression of multiple sclerosis.

Our finding that the Bifidobacterium-to-Akkermansia ratio may be a key marker for multiple sclerosis severity could help improve diagnosis and treatment. It also highlights how losing beneficial gut bacteria can allow other gut bacteria to become harmful, though it is unclear whether changing levels of certain microbes can affect multiple sclerosis.

While more research can help clarify the link between the gut microbiome and multiple sclerosis, these findings offer a promising new direction for understanding and treating this disease.

Ashutosh Mangalam, Associate Professor of Pathology, University of Iowa

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Ross Lazear, University at Albany, State University of New York

Curious Kids is a series for children of all ages. If you have a question you’d like an expert to answer, send it to curiouskidsus@theconversation.com.

How are clouds’ shapes made? – Amanda, age 5, Chile

I’m a meteorologist, and I’ve been fascinated by weather since I was 8 years old. I grew up in Minnesota, where the weather changes from wind-whipping blizzards in winter to severe thunderstorms – sometimes with tornadoes – in the summer. So, it’s not all that surprising that I’ve spent most of my life looking at clouds.

All clouds form as a result of saturation – that’s when the air contains so much water vapor that it begins producing liquid or ice.

Once you understand how certain clouds develop their shapes, you can learn to forecast the weather.

Cotton ball cumulus clouds

Clouds that look like cartoon cotton balls or cauliflower are made up of tiny liquid water droplets and are called cumulus clouds.

Often, these are fair-weather clouds that form when the Sun warms the ground and the warm air rises. You’ll often see them on humid summer days.

However, if the air is particularly warm and humid, and the atmosphere above is much colder, cumulus clouds can rapidly grow vertically into cumulonimbus. When the edges of these clouds look especially crisp, it’s a sign that heavy rain or snow may be imminent.

Wispy cirrus are ice clouds

When cumulonimbus clouds grow high enough into the atmosphere, the temperature becomes cold enough for ice clouds, or cirrus, to form.

Clouds made up entirely of ice are usually more transparent. In some cases, you can see the Sun or Moon through them.

Cirrus clouds that forms atop a thunderstorm spread outward and can form anvil clouds. These clouds flatten on top as they reach the stratosphere, where the atmosphere begins to warm with height.

However, most cirrus clouds aren’t associated with storms at all. There are many ice clouds associated with tranquil weather that are simply regions of the atmosphere with more moisture but not precipitation.

Fog and stratus clouds

Clouds are a result of saturation, but saturated air can also exist at ground level. When this occurs, we call it fog.

In temperatures below freezing, fog can actually deposit ice onto objects at or near the ground, called rime ice.

When clouds form thick layers, we add the word “stratus,” or “layer,” to the name. Stratus can occur just above the ground, or a bit higher up – we call it altostratus then. It can occur even higher and become cirrostratus, or a layer or ice clouds.

If there’s enough moisture and lift, stratus clouds can create rain or snow. These are nimbostratus.

How mountains can create their own clouds

There are a number of other unique and beautiful cloud types that can form as air rises over mountain slopes and other topography.

Lenticular clouds, for example, can look like flying saucers hovering just above, or near, mountaintops. Lenticular clouds can actually form far from mountains, as wind over a mountain range creates an effect like ripples in a pond.

Rarer are banner clouds, which form from horizontally spinning air on one side of a mountain.

Wind plays a big role

You might have looked up at the sky and noticed one layer of clouds moving in a different direction from another. Clouds move along with the wind, so what you’re seeing is the wind changing direction with height.

Cirrus clouds at the level of the jet stream – often about 6 miles (10 kilometers), above the ground – can sometimes move at over 200 miles per hour (320 kilometers per hour). But because they are so high up, it’s often hard to tell how fast they are moving.

Hello, curious kids! Do you have a question you’d like an expert to answer? Ask an adult to send your question to CuriousKidsUS@theconversation.com. Please tell us your name, age and the city where you live.

And since curiosity has no age limit – adults, let us know what you’re wondering, too. We won’t be able to answer every question, but we will do our best.

Ross Lazear, Instructor in Atmospheric and Environmental Sciences, University at Albany, State University of New York

This article is republished from The Conversation under a Creative Commons license. Read the original article.