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Extreme heat silently accelerates aging on a molecular level − new research

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theconversation.com – Eunyoung Choi, Postdoctoral Associate in Gerontology, University of Southern California – 2025-03-04 13:44:00

Extreme heat increases the risk of a number of diseases, including kidney and heart conditions.
Spencer Platt/Getty Images

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.

Person wearing a shirt reading 'EXCESSIVE HEAT ALERT' handing water bottle to older adult sitting outside
Extreme heat is a public health issue.
AP Photo/Lynne Sladky

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.

Two people sitting with their backs against the corner of a blue building,
Certain populations are more vulnerable to extreme heat.
Angela Weiss/AFP via Getty Images

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.

U.S. map showing extreme caution level or higher heat days, with the greatest number of total heat days in the South
Large swaths of the U.S. population are experiencing long stretches of extreme heat, as this map of cumulative heat days from 2010 to 2016 shows.
Eunyoung Choi, CC BY-ND

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.The Conversation

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

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Being alone has its benefits − a psychologist flips the script on the ‘loneliness epidemic’

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theconversation.com – Virginia Thomas, Assistant Professor of Psychology, Middlebury – 2025-04-04 07:18:00

Studies show that choosing ‘me time’ is not a recipe for loneliness but can boost your creativity and emotional well-being.
FotoDuets/iStock via Getty Images Plus

Virginia Thomas, Middlebury

Over the past few years, experts have been sounding the alarm over how much time Americans spend alone.

Statistics show that we’re choosing to be solitary for more of our waking hours than ever before, tucked away at home rather than mingling in public. Increasing numbers of us are dining alone and traveling solo, and rates of living alone have nearly doubled in the past 50 years.

These trends coincided with the surgeon general’s 2023 declaration of a loneliness epidemic, leading to recent claims that the U.S. is living in an “anti-social century.”

Loneliness and isolation are indeed social problems that warrant serious attention, especially since chronic states of loneliness are linked with poor outcomes such as depression and a shortened lifespan.

But there is another side to this story, one that deserves a closer look. For some people, the shift toward aloneness represents a desire for what researchers call “positive solitude,” a state that is associated with well-being, not loneliness.

As a psychologist, I’ve spent the past decade researching why people like to be alone – and spending a fair amount of time there myself – so I’m deeply familiar with the joys of solitude. My findings join a host of others that have documented a long list of benefits gained when we choose to spend time by ourselves, ranging from opportunities to recharge our batteries and experience personal growth to making time to connect with our emotions and our creativity.

YouTube video
Being alone can help remind people who they are.

So it makes sense to me why people live alone as soon as their financial circumstances allow, and when asked why they prefer to dine solo, people say simply, “I want more me time.”

It’s also why I’m not surprised that a 2024 national survey found that 56% of Americans considered alone time essential for their mental health. Or that Costco is now selling “solitude sheds” where for around US$2,000 you can buy yourself some peace and quiet.

It’s clear there is a desire, and a market, for solitude right now in American culture. But why does this side of the story often get lost amid the warnings about social isolation?

I suspect it has to do with a collective anxiety about being alone.

The stigma of solitude

This anxiety stems in large part from our culture’s deficit view of solitude. In this type of thinking, the desire to be alone is seen as unnatural and unhealthy, something to be pitied or feared rather than valued or encouraged.

This isn’t just my own observation. A study published in February 2025 found that U.S. news headlines are 10 times more likely to frame being alone negatively than positively. This type of bias shapes people’s beliefs, with studies showing that adults and children alike have clear judgments about when it is – and importantly when it is not – acceptable for their peers to be alone.

This makes sense given that American culture holds up extraversion as the ideal – indeed as the basis for what’s normal. The hallmarks of extraversion include being sociable and assertive, as well as expressing more positive emotions and seeking more stimulation than the opposite personality – the more reserved and risk-averse introverts. Even though not all Americans are extraverts, most of us have been conditioned to cultivate that trait, and those who do reap social and professional rewards. In this cultural milieu, preferring to be alone carries stigma.

But the desire for solitude is not pathological, and it’s not just for introverts. Nor does it automatically spell social isolation and a lonely life. In fact, the data doesn’t fully support current fears of a loneliness epidemic, something scholars and journalists have recently acknowledged.

In other words, although Americans are indeed spending more time alone than previous generations did, it’s not clear that we are actually getting lonelier. And despite our fears for the eldest members of our society, research shows that older adults are happier in solitude than the loneliness narrative would lead us to believe.

YouTube video
It’s all a balancing act – along with solitude, you need to socialize.

Social media disrupts our solitude

However, solitude’s benefits don’t automatically appear whenever we take a break from the social world. They arrive when we are truly alone – when we intentionally carve out the time and space to connect with ourselves – not when we are alone on our devices.

My research has found that solitude’s positive effects on well-being are far less likely to materialize if the majority of our alone time is spent staring at our screens, especially when we’re passively scrolling social media.

This is where I believe the collective anxiety is well placed, especially the focus on young adults who are increasingly forgoing face-to-face social interaction in favor of a virtual life – and who may face significant distress as a result.

Social media is by definition social. It’s in the name. We cannot be truly alone when we’re on it. What’s more, it’s not the type of nourishing “me time” I suspect many people are longing for.

True solitude turns attention inward. It’s a time to slow down and reflect. A time to do as we please, not to please anyone else. A time to be emotionally available to ourselves, rather than to others. When we spend our solitude in these ways, the benefits accrue: We feel rested and rejuvenated, we gain clarity and emotional balance, we feel freer and more connected to ourselves.

But if we’re addicted to being busy, it can be hard to slow down. If we’re used to looking at a screen, it can be scary to look inside. And if we don’t have the skills to validate being alone as a normal and healthy human need, then we waste our alone time feeling guilty, weird or selfish.

The importance of reframing solitude

Americans choosing to spend more time alone is indeed a challenge to the cultural script, and the stigmatization of solitude can be difficult to change. Nevertheless, a small but growing body of research indicates that it is possible, and effective, to reframe the way we think about solitude.

For example, viewing solitude as a beneficial experience rather than a lonely one has been shown to help alleviate negative feelings about being alone, even for the participants who were severely lonely. People who perceive their time alone as “full” rather than “empty” are more likely to experience their alone time as meaningful, using it for growth-oriented purposes such as self-reflection or spiritual connection.

Even something as simple as a linguistic shift – replacing “isolation” with “me time” – causes people to view their alone time more positively and likely affects how their friends and family view it as well.

It is true that if we don’t have a community of close relationships to return to after being alone, solitude can lead to social isolation. But it’s also true that too much social interaction is taxing, and such overload negatively affects the quality of our relationships. The country’s recent gravitational pull toward more alone time may partially reflect a desire for more balance in a life that is too busy, too scheduled and, yes, too social.

Just as connection with others is essential for our well-being, so is connection with ourselves.The Conversation

Virginia Thomas, Assistant Professor of Psychology, Middlebury

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Hard work feels worth it, but only after it’s done – new research on how people value effort

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theconversation.com – Piotr Winkielman, Professor of Psychology, University of California, San Diego – 2025-04-04 07:16:00

How many stairs would you climb for that payoff?
Ozgur Donmaz/DigitalVision via Getty Images

Piotr Winkielman, University of California, San Diego and Przemysław Marcowski, University of California, San Diego

When deciding if something is worth the effort, whether you’ve already exerted yourself or face the prospect of work changes your calculus. That’s what we found in our new research, published in the Journal of Experimental Psychology: General.

When you consider a future effort, more work makes the outcome less appealing. But once you’ve completed the work, more effort makes the outcome seem more valuable. We also discovered that hiding behind this general principle of timing there are individual differences in how future and past effort shapes people’s value for the fruits of their labor.

What’s it worth to you?

In our experiment, we gave participants a choice between a fixed amount of money and a household item – a mug – that they could take home if they exerted some amount of physical effort, roughly equivalent to walking up one, two or three flights of stairs.

This setup allowed us to determine the value each person placed on the effort – did it add to or subtract from the value of the item? For instance, if putting in a little more effort made someone switch their decision and decide to go with the cash instead of the mug, we could tell that they valued the mug plus that amount of effort less than that sum of money.

We also manipulated the time aspect of effort. When the effort was in the future, participants decided whether they wanted to go with the cash or get the mug with some effort. When the effort was in the past, participants decided whether they wanted to cash in the mug they had already earned with effort.

As we had expected, future effort generally detracted from the value of the mug, but the past effort generally increased it.

But these general trends do not tell the whole story. Not everyone responds to effort the same way. Our study also uncovered striking individual differences. Four distinct patterns emerged:

  1. For some people, extra effort always subtracted value.
  2. Others consistently preferred items with more work.
  3. Many showed mixed patterns, where moderate effort increased value but excessive effort decreased it.
  4. Some experienced the opposite: initially disliking effort, then finding greater value at higher levels.

These changing patterns show that one’s relationship with effort isn’t simple. For many people, there’s a sweet spot – a little effort might make something more valuable, but push too far and the value drops. It’s like enjoying a 30-minute workout but dreading a 2-hour session, or conversely, feeling that a 5-minute workout isn’t worth changing clothes for, but a 45-minute session feels satisfying.

Our paper offers a mathematical model that accounts for these individual differences by proposing that your mind flexibly computes costs and benefits of effort.

Why violate the ‘law of less work?’

Why should timing even matter for effort? It seems obvious that reason and nature would teach you to always avoid and dislike effort.

hummingbird hovers with beak approaching a flower
A hummingbird that puts in lots of extra work to get the same amount of nectar won’t last long.
Juan Carlos Vindas/Moment via Getty Images

A hummingbird that prefers a hard-to-get flower over an easy equal alternative might win an A for effort, but, exhausted, would not last long. The cruel world requires “resource rationality” – optimal, efficient use of limited physical and mental resources, balancing the benefits of actions with the required effort.

That insight is captured by the classic psychological “law of less work,” basically boiling down to the idea that given equivalent outcomes, individuals prefer easier options. Anything different would seem irrational or, in plain language, stupid.

If so, then how come people, and even animals, often prize things that require hard work for no additional payoff? Why is being hard-to-get a route to value? Anyone who has labored hard for anything knows that investing effort makes the final prize sweeter – whether in love, career, sports or Ikea furniture assembly.

Could the answer to this “paradox of effort” be that in the hummingbird example, the decision is about future effort, and in the Ikea effect, the effort is in the past?

Our new findings explain seemingly contradictory phenomena in everyday life. In health care, starting an exercise regimen feels overwhelming when focusing on upcoming workouts, but after establishing the habit, those same exercises become a source of accomplishment. At work, professionals might avoid learning difficult new skills, yet after mastering them, they value their enhanced abilities more because they were challenging to acquire.

JFK stands at a lectern outdoor in a sports stadium
John F. Kennedy supported space exploration efforts, ‘not because they are easy, but because they are hard.’
Robert Knudsen. White House Photographs. John F. Kennedy Presidential Library and Museum, Boston, CC BY

What still isn’t known

Sayings like “No pain, no gain” or “Easy come, easy go” populate our language and seem fundamental to our culture. But researchers still don’t fully understand why some people value effortful options more than others do. Is it physical aptitude, past experiences, a sense of meaning, perception of difficulty as importance or impossibility, moralization of effort, specific cultural beliefs about hard work? We don’t know yet.

We’re now studying how effort shapes different aspects of value: monetary value; hedonic value, as in the pleasure one gets from an item; and the aesthetic value, as in the sense of beauty and artistry. For instance, we’re investigating how people value artful calligraphy after exerting different amounts of effort to view it.

This work may shed light on curious cultural phenomena, like how people value their experience seeing the Mona Lisa after waiting for hours in crowds at the Louvre. These studies could also help researchers design better motivation systems across education, health care and business.The Conversation

Piotr Winkielman, Professor of Psychology, University of California, San Diego and Przemysław Marcowski, Postdoctoral Researcher in Decision Science, University of California, San Diego

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Susan Monarez, Trump’s nominee for CDC director, faces an unprecedented and tumultuous era at the agency

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theconversation.com – Jordan Miller, Teaching Professor of Public Health, Arizona State University – 2025-04-03 07:21:00

Susan Monarez, Trump’s nominee for CDC director, faces an unprecedented and tumultuous era at the agency

The Trump administration laid off thousands more employees at the CDC on April 1, 2025, as part of its workforce reduction.
Anadolu/Getty Images

Jordan Miller, Arizona State University

The job of director of the Centers for Disease Control and Prevention carries immense responsibility for shaping health policies, responding to crises and maintaining trust in public health institutions.

Since the Trump administration took office in January 2025, the position has been held on an interim basis by Susan Monarez, whom Trump has now nominated to take the job permanently after his first nominee, former Florida Congressman David Weldon, was withdrawn, in part over his anti-vaccine views.

Monarez, in contrast, is a respected scientist who endorses vaccines and has robust research experience. While she is new to the CDC, she is an accomplished public servant, having worked in several other agencies over the course of her career.

Monarez’s nomination comes at a time when the Department of Health and Human Services is in the midst of mass layoffs, and health professionals – and many in the public – have lost confidence in the federal government’s commitment to supporting evidence-based public health and medicine.

After having already cut nearly 10% of the CDC’s employees earlier in the year, the White House laid off thousands more HHS employees on April 1, gutting the CDC’s workforce by more than 24% in total.

As a teaching professor and public health educator, I appreciate the importance of evidence-based public health practice and the CDC director’s role in advancing public health science, disease surveillance and response and a host of other functions that are essential to public health.

The CDC is essential to promoting and protecting health in the U.S. and abroad, and the next director will shape its course in a challenging era.

A critical time for public health

In addition to the massive overhaul of the country’s public health infrastructure, the U.S. also faces a multistate measles outbreak and growing concerns over avian flu. Cuts to both the workforce and federal programs are hobbling measles outbreak response efforts and threatening the country’s ability to mitigate avian flu.

The Trump administration has also brought in several individuals who have long held anti-science views.

Robert F. Kennedy Jr.’s appointment to head of the Department of Health and Human Services was widely condemned by health experts, given his lack of credentials and history of spreading health misinformation.

So the stakes are high for the CDC director, who will report directly to Kennedy.

Two women hold protest signs about CDC layoffs along a roadside.
Two CDC workers – one who has been at the agency for 25 years and the other for 10 – protest mass layoffs on April 1, 2025.
AP Photo/Ben Gray

An abrupt pivot

Prior to his inauguration, Trump had signaled he would nominate Weldon, a physician who has promoted anti-vaccine theories.

But in March, Trump withdrew Weldon’s nomination less than an hour before his confirmation hearing was set to begin, after several Republicans in Congress relayed that they would not support his appointment.

Instead, Trump tapped Monarez for the top spot.

The role of a CDC director

The CDC relies on its director to provide scientific leadership, shape policy responses and guide the agency’s extensive workforce in addressing emerging health threats.

Prior to January, the CDC director was appointed directly by the president. The position did not require Senate confirmation, unlike the other HHS director positions. The selection was primarily an executive decision, although it was often influenced by political, public health and scientific considerations. But as of Jan. 20, changes approved in the 2022 omnibus budget require Senate confirmation for incoming CDC directors.

In the past, the appointed individual was typically a highly respected figure in public health, epidemiology or infectious disease, with experience leading large organizations, shaping policy and responding to public health emergencies. Public health policy experts expect that requiring Senate confirmation will enhance the esteem associated with the position and lend weight to the person who ultimately steps into the role. Yet, some have expressed concern that the position could become increasingly politicized.

Who is Susan Monarez?

Monarez holds a Ph.D. in microbiology and immunology. She has been serving as acting director of the CDC since being appointed to the interim position by Donald Trump on Jan. 24.

Prior to stepping into this role, she had been serving as deputy director for the Advanced Research Projects Agency for Health, or ARPA-H, since January 2023, a newer initiative established in 2022 through a US$1 billion appropriation from Congress to advance biomedical research.

Monarez has robust research experience, as well as administrative and leadership bona fides within the federal government. In the past, she has explored artificial intelligence and machine learning for population health. Her research has examined the intersection between technology and health and antimicrobial resistance, and she has led initiatives to expand access to behavioral and mental health care, reduce health disparities in maternal health, quell the opioid epidemic and improve biodefense and pandemic preparedness.

Monarez has not yet laid out her plans, but she will no doubt have a challenging role, balancing the interests of public health with political pressures.

Reactions to her nomination

Reactions to Monarez’s nomination among health professionals have been mostly positive. For instance, Georges Benjamin, executive director of the American Public Health Association, remarked that he appreciates that she is an active researcher who respects science.

But some have advocated for her to take a more active role in protecting public health from political attacks.

In her interim position, Monarez has not resisted Trump’s executive orders, even those that are widely seen by other health professionals as harmful to public health.

Since taking office, the current Trump administration has issued directives to remove important health-related data from government websites and has discouraged the use of certain terms in federally funded research.

Monarez has not pushed back on those directives, even though some of her own research includes key terms that would now be flagged in the current system, like “health equity”, and that health leaders expressed concerns in a letter sent to Monarez in January.

A photo of Susan Monarez.
One of the duties of Susan Monarez, the nominee to lead the CDC, is to communicate critical health information to the public.
NIH/HHS/Public domain

CDC staff have said that Monarez has not been visible as acting director. As of early April, she has not attended any all-hands meetings since she joined the CDC in January, nor has she held the advisory committee to the director meeting that is typically held every February. One agency higher-up described her as a “nonentity” in her role so far. Monarez has also reportedly been involved in decisions to drastically cut the CDC workforce.

While some have commented on the fact that she is the first nonphysician to head the agency in decades, that may actually be an advantage. The CDC’s primary functions are in scientific research and applying that research to improve public health. Doctoral scientists receive significantly more training in conducting research than medical doctors, whose training rightly prioritizes clinical practice, with many medical schools providing no training in research at all. Monarez’s qualifications are well-aligned with the requirements of the director role.

A time of change

The CDC was founded at a time of great change, in the aftermath of World War II.

Now, in 2025, the U.S. is again at a time of change, with the advent of powerful technologies that will affect public health in still unforeseeable ways. New and emerging infectious diseases, like measles, COVID-19 and Ebola, are sparking outbreaks that can spread quickly in population-dense cities.

A shifting health information ecosystem can spread health misinformation and disinformation rapidly. Political ideologies increasingly devalue health and science.

All these factors pose real threats to health in the U.S. and globally.

The next CDC director will undoubtedly play a key role in how these changes play out, both at home and abroad.

This story is part of a series of profiles of Cabinet and high-level administration positions.The Conversation

Jordan Miller, Teaching Professor of Public Health, Arizona State University

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

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