Potentially fatal combinations of humidity and heat are emerging across the globe

High temperature on thermometer (stock image).

Most everyone knows that humid heat is harder to handle than the "dry" kind. And recently, some scientists have projected that later in the century, in parts of the tropics and subtropics, warming climate could cause combined heat and humidity to reach levels rarely if ever experienced before by humans. Such conditions would ravage economies, and possibly even surpass the physiological limits of human survival.

According to a new study, the projections are wrong: such conditions are already appearing. The study identifies thousands of previously rare or unprecedented bouts of extreme heat and humidity in Asia, Africa, Australia, South America and North America, including in the U.S. Gulf Coast region. Along the Persian Gulf, researchers spotted more than a dozen recent brief outbreaks surpassing the theoretical human survivability limit. The outbreaks have so far been confined to localized areas and lasted just hours, but they are increasing in frequency and intensity, say the authors. The study appears this week in the journal Science Advances.

"Previous studies projected that this would happen several decades from now, but this shows it's happening right now," said lead author Colin Raymond, who did the research as a PhD. student at Columbia University's Lamont-Doherty Earth Observatory. "The times these events last will increase, and the areas they affect will grow in direct correlation with global warming."

Analyzing data from weather stations from 1979 to 2017, the authors found that extreme heat/humidity combinations doubled over the study period. Repeated incidents appeared in much of India, Bangladesh and Pakistan; northwestern Australia; and along the coasts of the Red Sea and Mexico's Gulf of California. The highest, potentially fatal, readings, were spotted 14 times in the cities of Dhahran/Damman, Saudi Arabia; Doha, Qatar; and Ras Al Khaimah, United Arab Emirates, which have combined populations of over 3 million. Parts of southeast Asia, southern China, subtropical Africa and the Caribbean were also hit.

The southeastern United States saw extreme conditions dozens of times, mainly near the Gulf Coast in east Texas, Louisiana, Mississippi, Alabama and the Florida Panhandle. The worst spots: New Orleans and Biloxi, Miss. Such conditions also reached inland into Arkansas and along the southeastern coastal plain.

Not surprisingly, incidents tended to cluster on coastlines along confined seas, gulfs and straits, where evaporating seawater provides abundant moisture to be sucked up by hot air. In some areas further inland, moisture-laden monsoon winds or wide areas of crop irrigation appear to play the same role.

Prior climate studies failed to recognize most past incidents because climate researchers usually look at averages of heat and humidity measured over large areas and over several hours at a time. Raymond and his colleagues instead drilled directly into hourly data from 7,877 individual weather stations, allowing them to pinpoint shorter-lived bouts affecting smaller areas.

Humidity worsens the effects of heat because humans cool their bodies by sweating; water expelled through the skin removes excess body heat, and when it evaporates, it carries that heat away. The process works nicely in deserts, but less well in humid regions, where the air is already too laden with moisture to take on much more. Evaporation of sweat slows. In the most extreme instances, it could stop. In that case, unless one can retreat to an air-conditioned room, the body's core heats beyond its narrow survivable range, and organs begin to fail. Even a strong, physically fit person resting in the shade with no clothes and unlimited access to drinking water would die within hours.

Meteorologists measure the heat/humidity effect on the so-called "wet bulb" Centigrade scale; in the United States, these readings are often translated into "heat index" or "real-feel" Fahrenheit readings. Prior studies suggest that even the strongest, best-adapted people cannot carry out normal outdoor activities when the wet bulb hits 32 C, equivalent to a heat index of 132 F. Most others would crumble well before that. A reading of 35 -- the peak briefly reached in the Persian Gulf cities -- is considered the theoretical survivability limit. That translates roughly to a heat index of 160 F. (The heat index actually ends at 127 F, so these readings are literally off the charts.) "It's hard to exaggerate the effects of anything that gets into the 30s," said Raymond.

The study found that worldwide, wet-bulb readings approaching or exceeding 30C on the wet bulb have doubled since 1979. The number of readings of 31 -- previously believed to occur only rarely -- totaled around 1,000. Readings of 33 -- previously thought to be almost nonexistent -- totaled around 80.

A heat wave that struck much of the United States last July maxed out at about 30C on the wet bulb, translating into heat indexes approaching 115 F in places; the highest was 122 F, in Baltimore, Md., and a similar wave hit in August. The waves paralyzed communities and led to at least a half-dozen deaths, including those of an air-conditioning technician in Phoenix, Az., and former National Football League lineman Mitch Petrus, who died in Arkansas while working outside.

It was a modest toll; heat-related illnesses already kill more U.S. residents than any other weather-related hazard including cold, hurricanes or floods. An investigation last year by the website InsideClimate News revealed that cases of heat stroke or heat exhaustion among U.S. troops on domestic bases grew 60 percent from 2008 to 2018. Seventeen soldiers died, almost all in the muggy U.S. Southeast. High-humidity heat waves in Russia and Europe, where far fewer people have air conditioning, have killed tens of thousands.

"We may be closer to a real tipping point on this than we think," said Radley Horton, a Lamont-Doherty research scientist and coauthor of the paper. Horton coauthored a 2017 paper projecting that such conditions would not take hold until later in the century.

While air conditioning may blunt the effects in the United States and some other wealthy countries, there are limits. Before the new study, one of the previously highest heat/humidity events ever reported was in the Iranian city of Bandar Mahshahr, which almost reached a 35C wet-bulb reading on July 31, 2015. There were no known deaths; residents reported staying inside air-conditioned vehicles and buildings, and showering after brief sojourns outside. But Horton points out that if people are increasingly forced indoors for longer periods, farming, commerce and other activities could potentially grind to a halt, even in rich nations-a lesson already brought home by the collapse of economies in the face of the novel coronavirus.

In any case, many people in the poorer countries most at risk do not have electricity, never mind air conditioning. There, many rely on subsistence farming requiring daily outdoor heavy labor. These facts could make some of the most affected areas basically uninhabitable, says Horton.

Kristina Dahl, a climatologist at the Union of Concerned Scientists who led a study last year warning of increasing future heat and humidity in the United States, said the new paper shows "how close communities around the world are to the limits." She added that some localities may already be seeing conditions worse than the study suggests, because weather stations do not necessarily pick up hot spots in dense city neighborhoods built with heat-trapping concrete and pavement.

Steven Sherwood, a climatologist at the Australia's University of New South Wales, said, "These measurements imply that some areas of Earth are much closer than expected to attaining sustained intolerable heat. It was previously believed we had a much larger margin of safety."

The study was coauthored by Tom Matthews, a lecturer in climate science at Loughborough University in the United Kingdom. Colin Raymond is now a postdoctoral researcher at NASA's Jet Propulsion Laboratory.

Story Source:

Materials provided by Earth Institute at Columbia University. Original written by Kevin Krajick. Note: Content may be edited for style and length.

---

Journal Reference:

1. Colin Raymond, Tom Matthews, Radley M. Horton. The emergence of heat and humidity too severe for human tolerance. Science Advances, 2020; 6 (19): eaaw1838 DOI: 10.1126/sciadv.aaw1838

Potentially fatal combinations of humidity and heat are emerging across the globe

Most everyone knows that humid heat is harder to handle than the "dry" kind. And recently, some scientists have projected that later in the century, in parts of the tropics and subtropics, warming climate could cause combined heat and humidity to reach levels rarely if ever experienced before by humans. Such conditions would ravage economies, and possibly even surpass the physiological limits of human survival.

According to a new study, the projections are wrong: such conditions are already appearing. The study identifies thousands of previously rare or unprecedented bouts of extreme heat and humidity in Asia, Africa, Australia, South America and North America, including in the U.S. Gulf Coast region. Along the Persian Gulf, researchers spotted more than a dozen recent brief outbreaks surpassing the theoretical human survivability limit. The outbreaks have so far been confined to localized areas and lasted just hours, but they are increasing in frequency and intensity, say the authors. The study appears this week in the journal Science Advances.

"Previous studies projected that this would happen several decades from now, but this shows it's happening right now," said lead author Colin Raymond, who did the research as a PhD. student at Columbia University's Lamont-Doherty Earth Observatory. "The times these events last will increase, and the areas they affect will grow in direct correlation with global warming."

Analyzing data from weather stations from 1979 to 2017, the authors found that extreme heat/humidity combinations doubled over the study period. Repeated incidents appeared in much of India, Bangladesh and Pakistan; northwestern Australia; and along the coasts of the Red Sea and Mexico's Gulf of California. The highest, potentially fatal, readings, were spotted 14 times in the cities of Dhahran/Damman, Saudi Arabia; Doha, Qatar; and Ras Al Khaimah, United Arab Emirates, which have combined populations of over 3 million. Parts of southeast Asia, southern China, subtropical Africa and the Caribbean were also hit.

The southeastern United States saw extreme conditions dozens of times, mainly near the Gulf Coast in east Texas, Louisiana, Mississippi, Alabama and the Florida Panhandle. The worst spots: New Orleans and Biloxi, Miss. Such conditions also reached inland into Arkansas and along the southeastern coastal plain.

Not surprisingly, incidents tended to cluster on coastlines along confined seas, gulfs and straits, where evaporating seawater provides abundant moisture to be sucked up by hot air. In some areas further inland, moisture-laden monsoon winds or wide areas of crop irrigation appear to play the same role.

Prior climate studies failed to recognize most past incidents because climate researchers usually look at averages of heat and humidity measured over large areas and over several hours at a time. Raymond and his colleagues instead drilled directly into hourly data from 7,877 individual weather stations, allowing them to pinpoint shorter-lived bouts affecting smaller areas.

Humidity worsens the effects of heat because humans cool their bodies by sweating; water expelled through the skin removes excess body heat, and when it evaporates, it carries that heat away. The process works nicely in deserts, but less well in humid regions, where the air is already too laden with moisture to take on much more. Evaporation of sweat slows. In the most extreme instances, it could stop. In that case, unless one can retreat to an air-conditioned room, the body's core heats beyond its narrow survivable range, and organs begin to fail. Even a strong, physically fit person resting in the shade with no clothes and unlimited access to drinking water would die within hours.

Meteorologists measure the heat/humidity effect on the so-called "wet bulb" Centigrade scale; in the United States, these readings are often translated into "heat index" or "real-feel" Fahrenheit readings. Prior studies suggest that even the strongest, best-adapted people cannot carry out normal outdoor activities when the wet bulb hits 32 C, equivalent to a heat index of 132 F. Most others would crumble well before that. A reading of 35 -- the peak briefly reached in the Persian Gulf cities -- is considered the theoretical survivability limit. That translates roughly to a heat index of 160 F. (The heat index actually ends at 127 F, so these readings are literally off the charts.) "It's hard to exaggerate the effects of anything that gets into the 30s," said Raymond.

The study found that worldwide, wet-bulb readings approaching or exceeding 30C on the wet bulb have doubled since 1979. The number of readings of 31 -- previously believed to occur only rarely -- totaled around 1,000. Readings of 33 -- previously thought to be almost nonexistent -- totaled around 80.

A heat wave that struck much of the United States last July maxed out at about 30C on the wet bulb, translating into heat indexes approaching 115 F in places; the highest was 122 F, in Baltimore, Md., and a similar wave hit in August. The waves paralyzed communities and led to at least a half-dozen deaths, including those of an air-conditioning technician in Phoenix, Az., and former National Football League lineman Mitch Petrus, who died in Arkansas while working outside.

It was a modest toll; heat-related illnesses already kill more U.S. residents than any other weather-related hazard including cold, hurricanes or floods. An investigation last year by the website InsideClimate News revealed that cases of heat stroke or heat exhaustion among U.S. troops on domestic bases grew 60 percent from 2008 to 2018. Seventeen soldiers died, almost all in the muggy U.S. Southeast. High-humidity heat waves in Russia and Europe, where far fewer people have air conditioning, have killed tens of thousands.

"We may be closer to a real tipping point on this than we think," said Radley Horton, a Lamont-Doherty research scientist and coauthor of the paper. Horton coauthored a 2017 paper projecting that such conditions would not take hold until later in the century.

While air conditioning may blunt the effects in the United States and some other wealthy countries, there are limits. Before the new study, one of the previously highest heat/humidity events ever reported was in the Iranian city of Bandar Mahshahr, which almost reached a 35C wet-bulb reading on July 31, 2015. There were no known deaths; residents reported staying inside air-conditioned vehicles and buildings, and showering after brief sojourns outside. But Horton points out that if people are increasingly forced indoors for longer periods, farming, commerce and other activities could potentially grind to a halt, even in rich nations-a lesson already brought home by the collapse of economies in the face of the novel coronavirus.

In any case, many people in the poorer countries most at risk do not have electricity, never mind air conditioning. There, many rely on subsistence farming requiring daily outdoor heavy labor. These facts could make some of the most affected areas basically uninhabitable, says Horton.

Kristina Dahl, a climatologist at the Union of Concerned Scientists who led a study last year warning of increasing future heat and humidity in the United States, said the new paper shows "how close communities around the world are to the limits." She added that some localities may already be seeing conditions worse than the study suggests, because weather stations do not necessarily pick up hot spots in dense city neighborhoods built with heat-trapping concrete and pavement.

Steven Sherwood, a climatologist at the Australia's University of New South Wales, said, "These measurements imply that some areas of Earth are much closer than expected to attaining sustained intolerable heat. It was previously believed we had a much larger margin of safety."

The study was coauthored by Tom Matthews, a lecturer in climate science at Loughborough University in the United Kingdom. Colin Raymond is now a postdoctoral researcher at NASA's Jet Propulsion Laboratory.

Potentially fatal combinations of humidity and heat are emerging across the globe

Mitochondria are the 'canary in the coal mine' for cellular stress

Illustration of mitochondria (stock image).

Credit: © RAJCREATIONZS / Adobe Stock

Mitochondria, tiny structures present in most cells, are known for their energy-generating machinery. Now, Salk researchers have discovered a new function of mitochondria: they set off molecular alarms when cells are exposed to stress or chemicals that can damage DNA, such as chemotherapy. The results, published online in Nature Metabolism on December 9, 2019, could lead to new cancer treatments that prevent tumors from becoming resistant to chemotherapy.

"Mitochondria are acting as a first line of defense in sensing DNA stress. The mitochondria tell the rest of the cell, 'Hey, I'm under attack, you better protect yourself,'" says Gerald Shadel, a professor in Salk's Molecular and Cell Biology Laboratory and the Audrey Geisel Chair in Biomedical Science.

Most of the DNA that a cell needs to function is found inside the cell's nucleus, packaged in chromosomes and inherited from both parents. But mitochondria each contain their own small circles of DNA (called mitochondrial DNA or mtDNA), passed only from a mother to her offspring. And most cells contain hundreds -- or even thousands -- of mitochondria.

Shadel's lab group previously showed that cells respond to improperly packaged mtDNA similarly to how they would react to an invading virus -- by releasing it from mitochondria and launching an immune response that beefs up the cell's defenses.

In the new study, Shadel and his colleagues set out to look in more detail at what molecular pathways are activated by the release of damaged mtDNA into the cell's interior. They homed in on a subset of genes known as interferon-stimulated genes, or ISGs, that are typically activated by the presence of viruses. But in this case, the team realized, the genes were a particular subset of ISGs turned on by viruses. And this same subset of ISGs is often found to be activated in cancer cells that have developed resistance to chemotherapy with DNA-damaging agents like doxyrubicin.

To destroy cancer, doxyrubicin targets the nuclear DNA. But the new study found that the drug also causes the damage and release of mtDNA, which in turn activates ISGs. This subset of ISGs, the group discovered, helps protect nuclear DNA from damage -- and, thus, causes increased resistance to the chemotherapy drug. When Shadel and his colleagues induced mitochondrial stress in melanoma cancer cells, the cells became more resistant to doxyrubicin when grown in culture dishes and even in mice, as higher levels of the ISGs were protecting the cell's DNA.

"Perhaps the fact that mitochondrial DNA is present in so many copies in each cell, and has fewer of its own DNA repair pathways, makes it a very effective sensor of DNA stress," says Shadel.

Most of the time, he points out, it's probably a good thing that the mtDNA is more prone to damage -- it acts like a canary in a coal mine to protect healthy cells. But in cancer cells, it means that doxyrubicin -- by damaging mtDNA first and setting off molecular alarm bells -- can be less effective at damaging the nuclear DNA of cancer cells.

"It says to me that if you can prevent damage to mitochondrial DNA or its release during cancer treatment, you might prevent this form of chemotherapy resistance," Shadel says.

His group is planning future studies on exactly how mtDNA is damaged and released and which DNA repair pathways are activated by the ISGs in the cell's nucleus to ward off damage.

Other authors on the study were Zheng Wu, Kailash Mangalhara, Alva Sainz, Laura Newman, Victoria Tripple and Susan Kaech of Salk; Sebastian Oeck, Lizhen Wu, Qin Yan, Marcus Bosenberg, Yanfeng Liu, Parker Sulkowski and Peter Glazer of Yale School of Medicine; Phillip West of Texas A&M College of Medicine; and Xiao-Ou Zhang of University of Massachusetts Medical School.

The work and the researchers involved were supported by grants from the National Institutes of Health, the Cancer Prevention and Research Institute of Texas, the Office of the Assistant Secretary of Defense for Health Affairs, the China Scholarship Counsel, the Salk Excellerators Postdoctoral Fellowship, and the George E. Hewitt Foundation for Medical Research Postdoctoral Fellowship.

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Story Source:

Materials provided by Salk Institute. Note: Content may be edited for style and length.

Mitochondria are the 'canary in the coal mine' for cellular stress

Illustration of mitochondria

Mitochondria, tiny structures present in most cells, are known for their energy-generating machinery. Now, Salk researchers have discovered a new function of mitochondria: they set off molecular alarms when cells are exposed to stress or chemicals that can damage DNA, such as chemotherapy. The results, published online in Nature Metabolism on December 9, 2019, could lead to new cancer treatments that prevent tumors from becoming resistant to chemotherapy.

"Mitochondria are acting as a first line of defense in sensing DNA stress. The mitochondria tell the rest of the cell, 'Hey, I'm under attack, you better protect yourself,'" says Gerald Shadel, a professor in Salk's Molecular and Cell Biology Laboratory and the Audrey Geisel Chair in Biomedical Science.

Most of the DNA that a cell needs to function is found inside the cell's nucleus, packaged in chromosomes and inherited from both parents. But mitochondria each contain their own small circles of DNA (called mitochondrial DNA or mtDNA), passed only from a mother to her offspring. And most cells contain hundreds -- or even thousands -- of mitochondria.

Shadel's lab group previously showed that cells respond to improperly packaged mtDNA similarly to how they would react to an invading virus -- by releasing it from mitochondria and launching an immune response that beefs up the cell's defenses.

In the new study, Shadel and his colleagues set out to look in more detail at what molecular pathways are activated by the release of damaged mtDNA into the cell's interior. They homed in on a subset of genes known as interferon-stimulated genes, or ISGs, that are typically activated by the presence of viruses. But in this case, the team realized, the genes were a particular subset of ISGs turned on by viruses. And this same subset of ISGs is often found to be activated in cancer cells that have developed resistance to chemotherapy with DNA-damaging agents like doxyrubicin.

To destroy cancer, doxyrubicin targets the nuclear DNA. But the new study found that the drug also causes the damage and release of mtDNA, which in turn activates ISGs. This subset of ISGs, the group discovered, helps protect nuclear DNA from damage -- and, thus, causes increased resistance to the chemotherapy drug. When Shadel and his colleagues induced mitochondrial stress in melanoma cancer cells, the cells became more resistant to doxyrubicin when grown in culture dishes and even in mice, as higher levels of the ISGs were protecting the cell's DNA.

"Perhaps the fact that mitochondrial DNA is present in so many copies in each cell, and has fewer of its own DNA repair pathways, makes it a very effective sensor of DNA stress," says Shadel.

Most of the time, he points out, it's probably a good thing that the mtDNA is more prone to damage -- it acts like a canary in a coal mine to protect healthy cells. But in cancer cells, it means that doxyrubicin -- by damaging mtDNA first and setting off molecular alarm bells -- can be less effective at damaging the nuclear DNA of cancer cells.

"It says to me that if you can prevent damage to mitochondrial DNA or its release during cancer treatment, you might prevent this form of chemotherapy resistance," Shadel says.

His group is planning future studies on exactly how mtDNA is damaged and released and which DNA repair pathways are activated by the ISGs in the cell's nucleus to ward off damage.

Other authors on the study were Zheng Wu, Kailash Mangalhara, Alva Sainz, Laura Newman, Victoria Tripple and Susan Kaech of Salk; Sebastian Oeck, Lizhen Wu, Qin Yan, Marcus Bosenberg, Yanfeng Liu, Parker Sulkowski and Peter Glazer of Yale School of Medicine; Phillip West of Texas A&M College of Medicine; and Xiao-Ou Zhang of University of Massachusetts Medical School.

The work and the researchers involved were supported by grants from the National Institutes of Health, the Cancer Prevention and Research Institute of Texas, the Office of the Assistant Secretary of Defense for Health Affairs, the China Scholarship Counsel, the Salk Excellerators Postdoctoral Fellowship, and the George E. Hewitt Foundation for Medical Research Postdoctoral Fellowship.

---

Story Source:

Materials provided by Salk Institute. Note: Content may be edited for style and length.

Why are giant pandas born so tiny?

Panda babies

Born pink, blind, and helpless, giant pandas typically weigh about 100 grams at birth -- the equivalent of a stick of butter. Their mothers are 900 times more massive than that.

This unusual size difference has left researchers puzzled for years. With a few exceptions among animals such as echidnas and kangaroos, no other mammal newborns are so tiny relative to their mothers. No one knows why, but a Duke University study of bones across 10 species of bears and other animals finds that some of the current theories don't hold up.

Duke biology professor Kathleen Smith and her former student Peishu Li published their findings this month in the Journal of Anatomy.

Baby panda skeletons are hard to come by, but the researchers were able to study the preserved remains of baby pandas born at the Smithsonian's National Zoo in Washington, D.C.

The National Zoo's first panda couple, Ling-Ling and Hsing-Hsing, had five full-term cubs in the 1980s, but none of them survived long after birth.

The researchers took micro-CT scans of two of those cubs, along with newborn grizzlies, sloth bears, polar bears, dogs, a fox, and other closely related animals from the Smithsonian National Museum of Natural History and the North Carolina State College of Veterinary Medicine.

They used the scans to create 3-D digital models of each baby's bony interior at birth.

As a baby animal grows and develops inside the womb, its bones and teeth do, too. The researchers examined the degree of ossification, or how much the skeleton has formed by the time of birth. They looked at whether the teeth had started to calcify or erupt, and the degree of fusion between the bony plates that make up the skull.

The panda may be an extreme example, but all bears have disproportionately small babies, Li said. A newborn polar bear's birthweight as a fraction of mom's is less than 1:400, or less than one-half of one percent of her body mass. For the vast majority of baby mammals, including humans, the average is closer to 1:26.

One decades-old idea links low birthweights in bears to the fact that, for some species, pregnancy overlaps with winter hibernation. Pregnant females don't eat or drink during this time, relying mostly on their fat reserves to survive, but also breaking down muscle to supply protein to the fetus.

The thinking is that, energetically, females can only afford to nourish their babies this way for so long before this tissue breakdown threatens their health. By cutting pregnancy short and giving birth to small, immature babies, bears would shift more of their growth to outside the womb, where babies can live off their mother's fat-rich milk instead of depleting her muscles.

Proponents of the theory concede that not all bears -- including pandas -- hibernate during the winter. But the idea is that small birthweight is 'locked in' to the bear family tree, preventing non-hibernating relatives from evolving bigger babies too.

"It's certainly an appealing hypothesis," Smith said.

But the Duke team's research shows this scenario is unlikely. The researchers didn't find any significant differences in bone growth between hibernating bears and their counterparts that stay active year-round and don't fast during pregnancy.

In fact, despite being small, the researchers found that most bear skeletons are just as mature at birth as their close animal cousins.

The panda bear is the one exception to this rule, results show. Even in a full-term baby panda, the bones look a lot like those of a beagle puppy delivered several weeks premature.

"That would be like a 28-week human fetus" at the beginning of the third trimester, Smith said.

Other factors might have pushed panda babies toward smaller sizes over time -- some researchers blame their bamboo-only diet -- but data are scarce, Li said. The researchers say the panda bear's embryonic appearance likely has to do with a quirk of panda pregnancy.

All bears experience what's called "delayed implantation." After the egg is fertilized, the future fetus enters a state of suspended animation, floating in the womb for several months before implanting in the uterine wall to resume its development and get ready for birth.

But while other bears gestate for two months after implantation, giant pandas are done in a month.

"They're basically undercooked," said Li, now a Ph.D. student at the University of Chicago.

The researchers say they only looked at skeletons in this study, and it could be that other organs like the brain tell a different story. But the new study suggests that baby pandas follow the same trajectory as other mammal relatives -- their bones mature in the same sequence and at similar rates -- but on a truncated timetable.

"Development is just cut short," Smith said.

Scientists are still searching for a complete explanation of why the panda's peculiar size differential evolved over geological time, and how.

"We really need more information about their ecology and reproduction in the wild," Smith said, and we may not have much time given their risk of extinction. But this study brings them one step closer to an answer.

This research was supported by a Shared Material Instrumentation Facility Undergraduate User Program grant, the Duke Department of Biology, and the Undergraduate Research Office at Duke.

Story Source:

Materials provided by Duke University. Original written by Robin A. Smith. Note: Content may be edited for style and length.

Brains of girls and boys are similar, producing equal math ability

Children with math on blackboard

In 1992, Teen Talk Barbie was released with the controversial voice fragment, "Math class is hard." While the toy's release met with public backlash, this underlying assumption persists, propagating the myth that women do not thrive in science, technology, engineering and mathematic (STEM) fields due to biological deficiencies in math aptitude.

Jessica Cantlon at Carnegie Mellon University led a research team that comprehensively examined the brain development of young boys and girls. Their research shows no gender difference in brain function or math ability. The results of this research are available online in the November 8 issue of the journal Science of Learning.

"Science doesn't align with folk beliefs," said Cantlon, the Ronald J. and Mary Ann Zdrojkowski Professor of Developmental Neuroscience at CMU's Dietrich College of Humanities and Social Sciences and senior author on the paper. "We see that children's brains function similarly regardless of their gender so hopefully we can recalibrate expectations of what children can achieve in mathematics."

Cantlon and her team conducted the first neuroimaging study to evaluate biological gender differences in math aptitude of young children.

Her team used functional MRI to measure the brain activity in 104 young children (3- to 10-years-old; 55 girls) while watching an educational video covering early math topics, like counting and addition. The researchers compared scans from the boys and girls to evaluate brain similarity. In addition, the team examined brain maturity by comparing the children's scans to those taken from a group of adults (63 adults; 25 women) who watched the same math videos.

After numerous statistical comparisons, Cantlon and her team found no difference in the brain development of girls and boys. In addition, the researchers found no difference in how boys and girls processed math skills and were equally engaged while watching the educational videos. Finally, boys' and girls' brain maturity were statistically equivalent when compared to either men or women in the adult group.

"It's not just that boys and girls are using the math network in the same ways but that similarities were evident across the entire brain," said Alyssa Kersey, postdoctoral scholar at the Department of Psychology, University of Chicago and first author on the paper. "This is an important reminder that humans are more similar to each other than we are different."

The researchers also compared the results of the Test of Early Mathematics Ability, a standardized test for 3- to 8-year-old children, from 97 participants (50 girls) to gauge the rate of math development. They found that math ability was equivalent among the children and did not show a difference in gender or with age. Nor did the team find a gender difference between math ability and brain maturity.

This study builds on the team's previous work that found equivalent behavioral performance on a range of mathematics tests between young boys and girls.

Cantlon said she thinks society and culture likely are steering girls and young women away from math and STEM fields. Previous studies show that families spend more time with young boys in play that involves spatial cognition. Many teachers also preferentially spend more time with boys during math class, predicting later math achievement. Finally, children often pick up on cues from their parent's expectations for math abilities.

"Typical socialization can exacerbate small differences between boys and girls that can snowball into how we treat them in science and math," Cantlon said. "We need to be cognizant of these origins to ensure we aren't the ones causing the gender inequities."

This project is focused on early childhood development using a limited set of math tasks. Cantlon wants to continue this work using a broader array of math skills, such as spatial processing and memory, and follow the children over many years.

Cantlon and Kersey were joined by Kelsey Csumitta at the University of Rochester on the study, titled "Gender Similarities in the Brain during Mathematics Development." This research received funding from the National Science Foundation and the National Institutes of Health.

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Story Source:

Materials provided by Carnegie Mellon University. Original written by Stacy Kish. Note: Content may be edited for style and length.

Teens are using a highly potent form of marijuana

Cannabis sativa plant

Nearly one in four Arizona teens have used a highly potent form of marijuana known as marijuana concentrate, according to a new study by Arizona State University researchers.

Among nearly 50,000 eighth, 10th, and 12th graders from the 2018 Arizona Youth Survey, a biennial survey of Arizona secondary school students, one-third (33%) had tried some form of marijuana, and nearly a quarter (24%) had tried marijuana concentrate.

Marijuana concentrates have about three times more THC, the constituent of marijuana that causes the "high," than a traditional marijuana flower. This is concerning because higher doses of THC have been linked to increased risk of marijuana addiction, cognitive impairment and psychosis, said the study's lead researcher, Madeline Meier, an ASU assistant professor of psychology.

The research team also found that teens who used concentrates had more risk factors for addiction. The researchers compared teens who had used marijuana concentrates with teens who had used some form of marijuana but not marijuana concentrates and teens who had never used any form of marijuana on known risk factors for addiction, such as lower perceived risk of harm of marijuana, peer substance use, parental substance use, academic failure and greater perceived availability of drugs in the community. They found that teens who had used marijuana concentrates were worse off on every addiction risk factor.

"This is important because it shows that teens who have a diverse array of risk factors for developing marijuana addiction may be further amplifying their risk for addiction by using high-THC marijuana concentrates," explained study co-author, Dustin Pardini, an associate professor in ASU's School of Criminology & Criminal Justice.

The study "Cannabis Concentrate Use in Adolescents," is published in the early online edition (Aug. 26, 2019) of Pediatrics.

The team -- which includes ASU researchers Meagan Docherty, School of Criminology & Criminal Justice; Scott Leischow, College of Health Solutions; and Kevin Grimm, Department of Psychology -- also found that teens who had used concentrates had much higher rates of e-cigarette use. One explanation for this might be that teens are using e-cigarettes to vape marijuana concentrate, according to Meier. Earlier studies, including those by Meier, have shown that youth put marijuana in e-cigarettes to conceal their marijuana use.

"Vaping marijuana can be passed off as nicotine vaping," Meier explained.

This finding reinforces the recent decision by the Food and Drug Administration to impose new restrictions on e-cigarettes and their constituents as a means of reducing marijuana use, according to the researchers.

Marijuana concentrates don't look like the traditional marijuana flower. Concentrates can look like wax, oil, or a brittle substance that shatters easily.

"What concerns me most is that parents might have no idea that their child is using marijuana, especially if their child is using marijuana concentrate," said Meier. "Marijuana is not harmless, particularly for adolescents."

Meier's earlier research suggests that frequent marijuana use from adolescence through adulthood is associated with IQ decline. Pardini's prior research has linked regular marijuana use during adolescence with the emergence of persistent subclinical psychotic symptoms.

The researchers' next steps are to ascertain if concentrate users do in fact exhibit higher rates of addiction, cognitive impairment and psychosis.

The Arizona Youth Survey is administered by the Arizona Criminal Justice Commission (ACJC) through funds appropriated by the Arizona Legislature.

Opioid prescription doses are increasingly being tapered, often more rapidly than recommended

Opiods

Stigma and safety fears have made daily dose tapering of opioid prescriptions more common. New research from UC Davis Health physicians, however, shows tapering can occur at rates as much as six times higher than recommended, putting patients at risk of withdrawal, uncontrolled pain or mental health crises.

The study -- "Trends and Rapidity of Dose Tapering Among Patients Prescribed Long-term Opioid Therapy, 2008-2017" -- is published in JAMA Network Open. The results also will be presented at the Nov. 16-19 North American Primary Care Research Group meeting in Toronto.

"Tapering plans should be based on the needs and histories of each patient and adjusted as needed to avoid adverse outcomes," said study author Alicia Agnoli, assistant professor of family and community medicine. "Unfortunately, a lot of tapering occurs due to policy pressures and a rush to get doses below a specific and sometimes arbitrary threshold. That approach can be detrimental in the long run."

In 2016, the U.S. Centers for Disease Control and Prevention (CDC) recommended dose tapering, or a slow reduction in prescription opioid doses over time, if the risks of continuing opioids outweigh the benefits. That point in time is usually when a patient is taking 90 morphine milligram equivalents -- or MMEs -- each day, and that dose is no longer reducing pain or improving daily functions. The CDC advises a slow decrease of 10% MMEs per month.

The study team set out to examine trends in opioid dose tapering and if tapering rates were consistent with CDC recommendations.

"We wanted to understand how often opioid dose tapering happens, how rapidly patients' doses were being reduced when tapering, and which patients were more likely to have doses tapered," said lead author Joshua Fenton, professor of family and community medicine.

Tapering faster than recommended

Fenton and Agnoli evaluated medical and pharmacy claims and enrollment records for more than 100,000 commercial insurance and Medicare Advantage enrollees, representing a diverse mixture of ages, races, ethnicities and locations across the U.S. They focused on individuals whose opioid doses were stable for at least a year and identified tapering patients as those with a 15% or more reduction in daily MMEs during a seven-month follow-up period.

They found that dose tapering became more common throughout the study period of 2008-2017, with the biggest jump following the CDC's 2016 prescribing guidelines. Tapering increased from 10.5% to 13.7% from 2008 to 2015, and from 16.2% to 22.4% from 2016 to 2017. Tapering was much more common in patients prescribed higher opioid dosages.

They also found that the rate of dose reduction often was well beyond the CDC's recommendation of 10% per month. The average reduction overall was 27.6% per month. Nearly 20% of patients tapered at a rate of 40% per month, and 5% tapered at a rate faster than 60% per month.

The 2016 policy could have been misinterpreted, leading many prescribers and health systems to insist on faster-than-recommended tapering, according to Agnoli.

"There is definitely a lot of pressure to reduce opioid use among patients, but there also is a need for more training and guidance for prescribers on how to help them safely do so," Agnoli said.

Women and tapering

Fenton and Agnoli also identified patient variables associated with tapering and uncovered an interesting difference in tapering rates based on sex.

While men have much higher rates of opioid use disorder and adverse outcomes related to opioids, women were more likely than men to have their opioid doses tapered.

"We think this has a lot to do with the gender dynamics of pain management and the physician-patient relationship," Agnoli said. "How women experience pain and discuss pain with their physicians is perhaps very different than men. There also could be some sex bias in terms of the patients that physicians choose to initiate conversations with about dose reduction."

Minimizing tapering risks

The researchers hope to build on this work to inform best practices for safe decision-making around dose reduction for all patients prescribed opioids.

"Ultimately, we want to clarify the effects of tapering on patients and how to help them taper to maximize benefits and minimize risks," Fenton said. "We expect this line of research will have important implications for how physicians manage and monitor patients who are undergoing opioid tapering."

Collaborators on this research were Guibo Xing, Daniel Tancredi, Anthony Jerant and Elizabeth Magnan of UC Davis Health, and Lillian Hang and Aylin Altan of OptumLabs in Minneapolis.

Their study was supported by UC Davis Health and OptumLabs and is available online.

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Story Source:

Materials provided by University of California - Davis Health. Note: Content may be edited for style and length.

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