Skip to content

Category: healthy living

Published on

Further reasons to be cautious of using antibiotics, and more support for finding beneficial bacteria and other microbes to outcompete the "bad" microbes. I especially liked the last paragraph that stressed for a healthy microbiota (microbial community):"Instead of trying to kill the "bad" bacteria causing an illness, a healthy and functioning microbiota may be able to outcompete the unwanted microbes and improve immune function." From Medical Xpress:

Unwanted impact of antibiotics broader, more complex than previously known

Researchers at Oregon State University have discovered that antibiotics have an impact on the microorganisms that live in an animal's gut that's more broad and complex than previously known. The findings help to better explain some of the damage these medications can do, and set the stage for new ways to study and offset those impacts.

Researchers have known for some time that antibiotics can have unwanted side effects, especially in disrupting the natural and beneficial microbiota of the gastrointestinal system. But the new study helps explain in much more detail why that is happening, and also suggests that powerful, long-term antibiotic use can have even more far-reaching effects. Scientists now suspect that antibiotic use, and especially overuse, can have unwanted effects on everything from the immune system to glucose metabolism, food absorption, obesity, stress and behavior.

The issues are rising in importance, since 40 percent of all adults and 70 percent of all children take one or more antibiotics every year, not to mention their use in billions of food animals. Although when used properly antibiotics can help treat life-threatening bacterial infections, more than 10 percent of people who receive the medications can suffer from adverse side effects.

This research used a "cocktail" of four antibiotics frequently given to laboratory animals, and studied the impacts."Prior to this most people thought antibiotics only depleted microbiota and diminished several important immune functions that take place in the gut," Morgun said. "Actually that's only about one-third of the picture. They also kill intestinal epithelium. Destruction of the intestinal epithelium is important because this is the site of nutrient absorption, part of our immune system and it has other biological functions that play a role in human health."

The research also found that antibiotics and antibiotic-resistant microbes caused significant changes in mitochondrial function, which in turn can lead to more epithelial cell death....Mitochondria plays a major role in cell signaling, growth and energy production, and for good health they need to function properly.

Morgun and Schulzhenko's research group also found that one of the genes affected by antibiotic treatment is critical to the communication between the host and microbe. "When the host microbe communication system gets out of balance it can lead to a chain of seemingly unrelated problems," Morgun said. Digestive dysfunction is near the top of the list, with antibiotic use linked to such issues as diarrhea and ulcerative colitis. But new research is also finding links to obesity, food absorption, depression, immune function, sepsis, allergies and asthma.

Healthy microbiota may also be another way to address growing problems with antibiotic resistance, Morgun said. Instead of trying to kill the "bad" bacteria causing an illness, a healthy and functioning microbiota may be able to outcompete the unwanted microbes and improve immune function.

Published on

Well DUH, of course eating organic foods lowers pesticide exposures. And yes, it can be measured in your body. So, as previous studies have shown, replacing regular fruits and vegetables (conventionally grown) with organic fruits and vegetables will lower your exposure to pesticides and the levels in your body.

And why is this important? Research shows health effects from pesticides, so it is healthier for you to lower your pesticide exposures - whether from eating food, or from your house and your yard (breathing it in, getting it on skin).

From Science Daily: Organic food reduces pesticide exposure

While health-conscious individuals understand the benefits of eating fresh fruits and veggies, they may not be aware of the amount of pesticides they could be ingesting along with their vitamin C and fiber. A new study to be published in the Feb. 5 edition of Environmental Health Perspectives is among the first to predict a person's pesticide exposure based on information about their usual diet.

Curl and her colleagues analyzed the dietary exposure of nearly 4,500 people from six U.S. cities to organophosphates (OPs), the most common insecticides used on conventionally grown produce in the United States. OP pesticides are linked to a number of detrimental health effects, particularly among agricultural workers who are regularly exposed to the chemicals.

Results showed that among individuals eating similar amounts of fruits and vegetables, those who reported eating organic produce had significantly lower OP pesticide exposures than those consuming conventionally grown produce. In addition, consuming those conventionally grown foods typically treated with more of these pesticides during production, including apples, nectarines and peaches, was associated with significantly higher levels of exposure. "For most Americans, diet is the primary source of OP pesticide exposure," said Curl "The study suggests that by eating organically grown versions of those foods highest in pesticide residues, we can make a measurable difference in the levels of pesticides in our bodies."

The researchers were able to predict each participant's exposure to OP pesticides based on the amount and type of produce each participant typically ate and the U.S. Department of Agriculture's measurements of pesticide residue levels on those foods. The researchers then compared these predictions to pesticide metabolite levels measured in urine samples from a subset of 720 of these people.

"The next step is to use these exposure predictions to examine the relationship between dietary exposure to pesticides and health outcomes, including neurological and cognitive endpoints. We'll be able to do that in this same population of nearly 4,500 people," she said.

One way people can reduce their pesticide exposure, said Curl, is to eat organic versions of those foods that are listed on the Environmental Working Group's "Dirty Dozen" list, which ranks fruits and vegetables according to pesticide residue level.

Published on

This is very interesting, and raises all sorts of possibilities for microbial transplants. While it's looking at only one person, this seems to be evidence that microbes are involved with our weight and manipulating them may result in weight gain or loss. From Science Daily:

Rapid and unexpected weight gain after fecal transplant

A woman successfully treated for a recurrent Clostridium difficile infection with stool from an overweight donor rapidly gained weight herself afterwards, becoming obese, according to a case report published in the new journal Open Forum Infectious Diseases.

Fecal microbiota transplant (FMT) is a promising treatment for relapsing C. difficile infections, a common cause of antibiotic-related diarrhea that in severe cases may be life-threatening. The case suggests that clinicians should avoid selecting stool donors who are overweight. The report also raises questions about the role of gut bacteria in metabolism and health.

At the time of the woman's fecal transplant in 2011, her weight was stable at 136 pounds, and her Body Mass Index (BMI) was 26. Then 32 years old, she had always been of normal weight. The transplant used donor stool from the woman's overweight but otherwise healthy teenage daughter, administered via colonoscopy, to restore a healthy balance of bacteria in the woman's gut, curing her C. difficile infection.

Sixteen months later, the woman weighed 170 pounds, and her BMI was 33, meeting medical criteria for obesity. The weight gain persisted despite a medically supervised liquid protein diet and exercise program. Continuing efforts to diet and exercise did not lower her weight: Three years after the transplant, she weighed 177 pounds with a BMI of 34.5, and she remains obese today.

"We're questioning whether there was something in the fecal transplant, whether some of those 'good' bacteria we transferred may have had an impact on her metabolism in a negative way," said Colleen R. Kelly, MD, of the Warren Alpert Medical School of Brown University, who wrote the case report with Neha Alang, MD, of Newport Hospital in Rhode Island. Such a link between bacteria in the gastrointestinal tract and weight is supported by previously published animal studies, where transfer of gut bacteria from obese to normal-weight mice can lead to a marked increase in fat. In light of the case and the animal data, the authors recommend selecting stool donors who are not overweight for fecal transplants.

Importantly, the FMT was not the only possible cause of the woman's weight gain. In addition to treatment for C. difficile, she had also been treated with several antibiotics for Helicobacter pylori infection. Other possible contributing factors in the woman's weight gain include the resolution of her C. difficile infection, genetic factors, aging, and stress related to illness. However, as noted above, she had never been overweight before.

Published on

Now we are finally finding out about all the microbes we encounter when go through New York City's subway system: touching handrails, turnstiles, and just sitting on benches. This study looked at the microbial communities of NYC's subway system. From the Wall Street Journal:

Big Data and Bacteria: Mapping the New York Subway’s DNA

Aboard a No. 6 local train in Manhattan, Weill Cornell researcher Christopher Mason patiently rubbed a nylon swab back and forth along a metal handrail, collecting DNA in an effort to identify the bacteria in the New York City subway. In 18 months of scouring the entire system, he has found germs that can cause bubonic plague uptown, meningitis in midtown, stomach trouble in the financial district and antibiotic-resistant infections throughout the boroughs.

The big-data project, the first genetic profile of a metropolitan transit system, is in many ways “a mirror of the people themselves who ride the subway,” said Dr. Mason, a geneticist at the Weill Cornell Medical College... By documenting the miniature wildlife, microbiologists hope to discover new ways to track disease outbreaks—including contagious diseases like Ebola or measles—detect bioterrorism attacks and combat the growing antibiotic resistance among microbes, which causes about 1.7 million hospital infections every year.“We know next to nothing about the ecology of urban environments,” said evolutionary biologist Jonathan Eisen at the University of California at Davis. “How will we know if there is something abnormal if we don’t know what normal is?”

Dr. Mason and his research team gathered DNA from turnstiles, ticket kiosks, railings and benches in a transit system shared by 5.5 million riders every day. They sequenced the genetic material they found at the subway’s 466 open stations—more than 10 billion fragments of biochemical code—and sorted it by supercomputer. They compared the results to genetic databases of known bacteria, viruses and other life-forms to identify these all-but-invisible fellow travelers.

In the process, they uncovered how commuters seed the city subways every day with bacteria from the food they eat, the pets or plants they keep, and their shoes, trash, sneezes and unwashed hands. The team detected signs of 15,152 types of life-forms. Almost half of the DNA belonged to bacteria—most of them harmless; the scientists said the levels of bacteria they detected pose no public-health problem. Data from the PathoMap Project, as Dr. Mason calls it, was published online in the journal Cell Systems on Thursday.

As more and more scientists probe urban microbiology, they are also hoping to find ways to foster beneficial bacteria through building design and to learn how to eliminate construction practices that create living conditions for the germs that make people ill.

This emerging field reflects the growing awareness that the human body swarms with bacteria. Typically, every person is home to about a hundred trillion microbial cells bearing five million different genes, totaling about 5 pounds of micro-organisms per person. Indeed, microbes in and on the body outnumber human cells about 10 to one. The body’s collection of microbes, called the microbiome, influences health in ways that researchers are only beginning to understand. 

Broadly speaking, city living leaves its mark on people. That includes the sorts of microbes that collect inside them. A recent comparison of urban and rural residents in Russia found that city dwellers had different sets of stomach microbes than people in the countryside. Every person trails a distinctive collection of microbes, by shedding about 1.5 million microscopic skin cells every hour. Bacteria from a person’s body can colonize a hotel room in less than six hours, scientists at the U.S. Department of Energy’s Argonne National Laboratory in Illinois recently discovered.

Depending on the material involved, some surfaces can have thousands of different types of bacteria while others may have only a few hundred, researchers monitoring the new Chicago hospital found. Pathogens responsible for common infections, such as the strep germs that cause an estimated 700 million infections world-wide every year, can survive for months on a dry surface, researchers in Germany reported in September in the journal BMC Infectious Diseases.

The New York subway study quickly hit the current limits of science. Most microbes have never been isolated or studied. Only a few thousand creatures of any sort have ever had their entire set of genes analyzed, so identifications of DNA sequences through online computer comparisons can be inaccurate. All told, the biodiversity of the subway isn’t as rich as normal soil. The dirt in Central Park contains 167,000 types of micro-organisms—about 11 times the number of species in the transit system... But a deep breath of subway air contains about as many free-floating bacteria as fresh air at street level, researchers at the University of Colorado Boulder reported last year in the journal Applied and Environmental Microbiology.

No two subway stations were exactly the same, said Weill Cornell project leader Ebrahim Afshinnekoo, who helped analyze the data.The greatest subway biodiversity was found at the Myrtle-Willoughby Avenue stop for the G train in Bedford-Stuyvesant, Brooklyn, where 95 unique bacteria groups were detected....Among the DNA of higher organisms, the researchers found across the system that genetic material from beetles and flies was the most prevalent—the cockroach genome hasn’t been sequenced yet so that DNA wasn’t identified... Human DNA ranked fourth.

So far, scientists have identified 562 species of bacteria, most of them benign or low risk. At least 67 of those species can make people sick. Even these infectious bacteria were all detected at such low levels that they were unlikely to cause illness in a healthy person...Among the pathogenic and infectious bacteria, the Cornell researchers identified DNA related to strep infections at 66 stations and urinary tract infections at 192 stations. They found E. coli at 56 stations and other bacteria related to food poisoning at 215 stations.

 

Published on

The possibility of lowering the risk of ischemic stroke (and poor recovery from it) is a good reason to try to increase vitamin D levels - by supplements and/or sunlight. Note that an ischemic stroke occurs when a blood vessel that supplies blood to the brain is blocked by a blood clot. From Medical Xpress:

Low vitamin D predicts more severe strokes, poor health post-stroke

Stroke patients with low vitamin D levels were found to be more likely than those with normal vitamin D levels to suffer severe strokes and have poor health months after stroke, according to research presented at the American Stroke Association's International Stroke Conference 2015. Low vitamin D has been associated in past studies with neurovascular injury (damage to the major blood vessels supplying the brain, brainstem, and upper spinal cord).

"Many of the people we consider at high risk for developing stroke have low vitamin D levels. Understanding the link between stroke severity and vitamin D status will help us determine if we should treat vitamin D deficiency in these high-risk patients," said Nils Henninger, M.D., senior study author and assistant professor of neurology and psychiatry at University of Massachusetts Medical School in Worchester.

Henninger and colleagues studied whether low blood levels of 25-hydroxyvitamin D, a marker of vitamin D status, is predictive of ischemic stroke severity and poor health after stroke in 96 stroke patients treated between January 2013 and January 2014 at a U.S. hospital. They found:

  • Overall, patients who had low vitamin D levels –defined as less than 30 nanograms per milliliter (ng/mL) – had about two-times larger areas of dead tissue resulting from obstruction of the blood supply compared to patients with normal vitamin D levels.
  • This association was similar among patients who suffered lacunar strokes (in which the small, intricate arteries of the brain are affected) and patients with non-lacunar strokes (such as those caused by carotid disease or by a clot that originated elsewhere in the body).
  • For each 10 ng/mL reduction in vitamin D level, the chance for healthy recovery in the three months following stroke decreased by almost half, regardless of the patient's age or initial stroke severity.

Published on

Interesting that less is best when it comes to jogging and health. Found U shaped association in health benefits from jogging: "Joggers who ran 1 to 2.4 hours per week had the lowest risk of mortality, with a significant 71% lower risk of death than sedentary nonjoggers. And in fact, the people who jogged the most frequently and at the fastest pace — who were, in effect, runners rather than joggers — did not enjoy much benefit in terms of mortality. In fact, their lifespans tended to be about the same as among people who did not exercise at all." From NY Times:

Slow Runners Come Out Ahead

The ideal amount of running for someone who wants to live a long and healthy life is less than most of us might expect, according to a new study, which also suggests that people can overdo strenuous exercise and potentially shorten their lives.

There is increasing consensus among physicians and exercise scientists that people should exercise intensely at least sometimes. Past studies have found, for instance, that walkers who move at a brisk pace tend to live longer than those who stroll, even if they cover about the same distance.

So for the new study, which was published this month in The Journal of the American College of Cardiology, the researchers, most of them affiliated with the University of Copenhagen, turned to the enormous database about health habits among Danes known as the Copenhagen City Heart Study. In this case, instead of focusing on cycling, the researchers decided to look at jogging, since it is the most popular strenuous activity worldwide.

The researchers culled data for 1,098 adult men and women of varying ages who, upon their entry into the study in 2001, had identified themselves as joggers. They also had provided information about how often they ran per week, at what pace, and for how long. The researchers also pulled records for 3,950 age-matched volunteers who had said in 2001 that they did not engage in any type of vigorous exercise or, in fact, any exercise at all. All of the volunteers were generally healthy, however, without evidence at the time of disease or obesity.

As it turned out, and as expected, joggers consistently tended to live longer than people who did not exercise. But when the researchers closely parsed the data about how much and how intensely people jogged, some surprises emerged. The ideal amount of jogging for prolonged life, this nuanced analysis showed, was between 1 hour and 2.4 hours each week. And the ideal pace was slow. 

Plodding joggers tended to live longer than those who were faster. And in fact, the people who jogged the most frequently and at the fastest pace — who were, in effect, runners rather than joggers — did not enjoy much benefit in terms of mortality. In fact, their lifespans tended to be about the same as among people who did not exercise at all. The results suggest that the “optimal dose of jogging is light, and strenuous joggers and sedentary non-joggers have similar mortality rates,” said Jacob Louis Marott, a researcher for the Copenhagen City Heart Study and co-author of the study.

More details and discussion are in the Medscape article.From Medscape:

Short, Easy—Not Strenuous—Jogging Gives Biggest Survival Gain: Analysis

Published on

Yes, this finding is important , but what should be also noted is this sentence in the article: "He also noted that it may not be a disease itself, but the treatment for the disease, that's actually responsible for reproductive malfunction." It has been known for decades that men's sperm is affected by environmental chemicals (such as pesticides), alcohol, smoking, and medications. So it's important to figure out if it's the medicine or the health condition that's causing the problem - or perhaps it's both. From Science Daily:

Infertility is a warning: Poor semen quality linked to hypertension, other health problems

A study of men who were evaluated for the cause of their infertility finds previously unknown relationships between deficiencies in their semen and other, seemingly unrelated health problems. A study of more than 9,000 men with fertility problems has revealed a correlation between the number of different defects in a man's semen and the likelihood that the man has other health problems.

The study, conducted by investigators at the Stanford University School of Medicine, also links poor semen quality to a higher chance of having various specific health conditions, such as hypertension, and more generally to skin and endocrine disorders....A study Eisenberg co-authored a few years ago showed that infertile men had higher rates of overall mortality, as well as mortality linked to heart problems, in the years following an infertility evaluation. 

In the new study, Eisenberg and his colleagues analyzed the medical records of 9,387 men, mostly between 30 and 50 years old, who had been evaluated at Stanford Hospital & Clinics (now Stanford Health Care) between 1994 and 2011 to determine the cause of their infertility. ...So, using the database, the investigators were able to compare the overall health status of men who had semen defects to that of the men who didn't.

With a median age of 38, this was a fairly young group of men. However, 44 percent of all the men had some additional health problem besides the fertility problem that brought them to the clinic. In particular, the investigators found a substantial link between poor semen quality and specific diseases of the circulatory system, notably hypertension, vascular disease and heart disease. 

In addition, as the number of different kinds of defects in a man's semen rose, so did his likelihood of having a skin disease or endocrine disorder. When looking at the severity of all health problems, the scientists observed a statistically significant connection between the number of different ways in which a man's semen was deficient and the likelihood of his having a substantial health problem.... He also noted that it may not be a disease itself, but the treatment for the disease, that's actually responsible for reproductive malfunction. He said he is exploring this possibility now.

This article mentions a few of the other issues that are linked with male infertility.While incomplete, at least it mentions smoking, BPA exposure, binge drinking, obesity, and lack of sleep.From Medical Daily:

Your Sperm And Your Health: What Your Semen Can Tell You About Your Health

The following article focused on other links to male infertility. It also discussed an interesting 2012 study that looked at the effects of wearing tight briefs (which heats the genitals) versus boxers on sperm production (hint: briefs had very negative effect). From Five Thirty Eight Science:

Men, Those Tightie Whities Really Are Killing Your Sperm Count

Published on

Much has been written about boxing, concussions, and brain damage, but this is the first time I've read about mixed martial art fighters also having such problems. But it makes sense. From Medscape:

Fight Exposure Linked to Reduced Brain Volume

The more boxers and martial arts practitioners experience head trauma, the more likely they are to have lower brain volume, particularly caudate and thalamus volume, according to a new study. Lower brain volume in these fighters correlated with reduced processing speed, the study also found.

These results "suggest that greater exposure to head trauma is related to detectable brain structural and performance deficits in active fighters," the authors, led by Charles Bernick, MD, Lou Ruvo Center for Brain Health, Cleveland Clinic, Las Vegas, Nevada, conclude.

The analysis included 224 adults, aged 18 to 44 years, who were participants in the Professional Fighters Brain Health Study, a longitudinal cohort study of boxers and mixed martial arts (MMA) fighters. The participants included 93 boxers and 131 MMA fighters.The length of professional fighting in this group ranged from 0 to 24 years, with a mean of 4 years. The number of professional fights ranged from 0 to 101, with a mean of 10 fights.

The study also included a control group of 22 age- and education-matched participants with no history of head trauma who did not play a sport associated with head injuries from high school onward.Participants were assessed at baseline and then annually for 4 years. Researchers measured cognitive function with a computer-based battery consisting of tests of  verbal memory, processing speed, and other functions. They used MRI to assess brain volumes.

The study found that increasing exposure to head trauma, as measured by the number of professional fights or years of professional fighting, was generally associated with lower brain structural volumes, particularly subcortical structures. The most consistent relationship between exposure variables and brain volume was seen in the thalamus and caudate. 

The thalamus acts as a "gateway" to the cortex and when affected can influence many neurologic functions, said the authors. It and the caudate are vulnerable to volumetric loss through several mechanisms. Rotational movement of the head brought on by punches in boxing or MMA can result in diffuse axonal injury in white matter tracts, they note.

For the most part, brain structure volumes were lower for boxers than MMA fighters or controls. This could be due to several factors, the authors write. "Perhaps the most obvious explanation is that boxers get hit in the head more. In addition to trying to concuss (ie, knock out) their opponent, MMA fighters can utilise other combat skills such as wrestling and jiu jitsu to win their match by submission without causing a concussion."

The study also found that processing speed was correlated with reduced volume in several cortical and subcortical structures. Reduction in processing speed, said the authors, is consistent with repeated concussions and is considered a clinical component of chronic traumatic encephalopathy.

Published on

Bottom line: try not to eat processed sweetened foods or drink sodas because high intake is linked to type 2 diabetes. Several studies point the finger in particular to high fructose corn syrup, which is the most frequently used sweetener in processed foods, particularly fruit-flavored drinks and soda. An earlier 2013 study from Europe found that drinking one 12-ounce sugar-sweetened soft drink a day can increase the risk of type 2 diabetes by 22%. Instead eat real whole foods like fruits and vegetables. From Medscape:

Added Sweeteners in Processed Foods Tied to Diabetes

A large body of evidence from animal studies and observational and clinical trials in humans suggests that eating processed foods with added sweeteners is contributing to the growing incidence of type 2 diabetes, a new review, published online January 29 in the Mayo Clinic Proceedings, concludes. Thus, "by limiting sugar to 5% to 10% of total caloric intake, the harmful effects of sugar, particularly fructose, on insulin resistance could be minimized," he and his colleagues conclude. This in turn "may protect against diabetes and its complications, including early mortality from cardiovascular causes."

About three-quarters of all packaged foods and beverages in the US contain added sugar, and it is estimated that Americans eat up to 22 to 47 teaspoons of sugar a day, including hidden sugar in processed foods, Dr DiNicolantonio said.

"High intakes of added sugars, especially in the form of sugar-sweetened beverages, are associated with an increased risk of type 2 diabetes." However, at the same time, "people should not be concerned about limiting fructose found in whole foods such as fruits and vegetables," she noted.

The AHA recommends limiting added sugars to no more than 6 tsp (24 g), or 100 calories, per day for women, and 9 tsp (36 g), or 150 calories, per day, for men and cutting sugar-sweetened beverage consumption to no more than 36 ounces, or 450 calories, per week.

From Science Daily:

Added fructose is a principal driver of type 2 diabetes, experts argue

Recent studies have shown that added sugars, particularly those containing fructose, are a principal driver of diabetes and pre-diabetes, even more so than other carbohydrates. Clinical experts challenge current dietary guidelines that allow up to 25 percent of total daily calories as added sugars, and propose drastic reductions in the amount of added sugar, and especially added fructose, people consume.

The totality of the evidence is compelling to suggest that added sugar, and especially added fructose (usually in the form of high-fructose corn syrup and table sugar), are a serious and growing public health problem, according to the authors.

While fructose is found naturally in some whole foods like fruits and vegetables, consuming these foods poses no problem for human health. Indeed, consuming fruits and vegetables is likely protective against diabetes and broader cardiometabolic dysfunction, explained DiNicolantonio and colleagues. The authors propose that dietary guidelines should be modified to encourage individuals to replace processed foods, laden with added sugars and fructose, with whole foods like fruits and vegetables. 

Published on

Very important research looking at some professional football players who started playing tackle football before the age of 12, and comparing them to those who started later. It discusses the issue of whether children should be playing tackle football before the age of 12 - these and other results suggest NOT. Wait till older (or don't play tackle at all).This article came from Boston University through Futurity:

Is This Kid Too Young For Football?

Researchers from Boston University School of Medicine found that former National Football League (NFL) players who participated in tackle football before the age of 12 are more likely to have memory and thinking problems as adults.

The study contradicts conventional wisdom that children’s more plastic brains might recover from injury better than those of adults, and suggests that they may actually be more vulnerable to repeated head impacts, especially if injuries occur during a critical period of growth and development. "

“This is one study, with limitations,” adds study senior author Robert Stern, a professor of neurology, neurosurgery, and anatomy and neurobiology and director of the Alzheimer’s Disease Center’s Clinical Core. “But the findings support the idea that it may not make sense to allow children—at a time when their brain is rapidly developing—to be exposed to repetitive hits to the head.”

In the study, researchers reexamined data from Boston University’s ongoing DETECT(Diagnosing and Evaluating Traumatic Encephalopathy Using Clinical Tests) study, which aims to develop methods of diagnosing chronic traumatic encephalopathy (CTE) during life. CTE is a neurodegenerative disease often found in professional football players, boxers, and other athletes who have a history of repetitive brain trauma. It can currently be diagnosed only by autopsy.

For this latest study, published in the journal Neurology, scientists examined test scores of 42 former NFL players, with an average age of 52, all of whom had experienced memory and thinking problems for at least six months. Half the players had played tackle football before age 12, and half had not. Significantly, the total number of concussions was similar between the two groups.

Researchers found that the players exposed to tackle football before age 12 had greater impairment in mental flexibility, memory, and intelligence—a 20 percent difference in some cases. These findings held up even after statistically removing the effects of the total number of years the participants played football. Both groups scored below average on many of the tests.

Stamm says the researchers were especially surprised by the scores on a reading test called the WRAT-4, which has participants read words of increasing difficulty....The low scores may be significant, she says, because they suggest that repeated head trauma at a young age might limit peak intelligence. She emphasizes, however, that there may be other reasons for a low score, and that more research is needed.

The authors chose age 12 as the cutoff because significant peaks in brain development occur in boys around that age. (This happens for girls a bit earlier, on average.) Around age 12, says Stern, blood flow to the brain increases, and brain structures such as the hippocampus, which is critical for memory, reach their highest volume.

Boys’ brains also reach a peak in their rate of myelination—the process in which the long tendrils of brain cells are coated with a fatty sheath, allowing neurons to communicate quickly and efficiently. Because of these developmental changes, Stern says, this age may possibly represent a “window of vulnerability,” when the brain may be especially sensitive to repeated trauma.

Stern adds that a study by another group of researchers of the number and severity of hits in football players aged 9 to 12, using accelerometers in helmets, found that players received an average of 240 high-magnitude hits per season, sometimes with a force similar to that experienced by high school and college players.

With approximately 4.8 million athletes playing youth football in the United States, the long-term consequences of brain injury represent a growing public health concern. This study comes at a time of increasing awareness of the dangers of concussions—and subconcussive hits—in youth sports like football, hockey, and soccer. In 2012, Pop Warner football, the oldest and largest youth football organization in the country, changed its rules to limit contact during practices and banned intentional head-to-head contact. 

“Football has the highest injury rate among team sports,” writes Christopher M. Filley, a fellow with the American Academy of Neurology, in an editorial accompanying the Neurology article. “Given that 70 percent of all football players in the United States are under the age of 14, and every child aged 9 to 12 can be exposed to 240 head impacts during a single football season, a better understanding of how these impacts may affect children’s brains is urgently needed.”