UI analysis finds significant increase in number of US children diagnosed with ADHD over 20 years

The number of children in the United States diagnosed with Attention Deficit/Hyperactivity Disorder (ADHD) increased from 6.1 percent to 10.2 percent from 1997 to 2016, according to an analysis from the University of Iowa published in the Journal of the American Medical Association (JAMA) Network Open.

A portrait of Assistant Professor Wei Bao of the Department of Epidemiology in the University of Iowa College of Public Health.
Wei Bao

This upward trend cut across all demographic subgroups, says Wei Bao, assistant professor of epidemiology in the UI College of Public Health and study co-author.

“Our findings indicate a continuous increase in the prevalence of diagnosed ADHD among U.S. children and adolescents,” says Bao.

The study analyzed the health information of more than 186,000 children and adolescents gathered by the U.S. National Health Interview Survey (NHIS), an annual survey of American households conducted by the U.S. Centers for Disease Control and Prevention. The data were collected annually from 1997 to 2016.

The analysis found that 1,243 children age 4 to 17 were reported to have ADHD in the 1997–98 survey, representing 6.1 percent of U.S. children and adolescents. That increased to 1,880 reported cases in 2015–16, representing 10.2 percent of U.S. children and adolescents.

The analysis also found this upward trend across gender, racial, family, and geographic lines. However, it found that not all increases were uniform, and that there were distinct differences within groups.

For instance, in the gender subgroup, the research showed 14 percent of boys were diagnosed with ADHD in 2016, up from 9 percent in 1997. However, only 6.3 percent of girls were diagnosed with ADHD in 2016, up from 3.1 percent in the 1997 survey.

While the number of Hispanic children diagnosed with ADHD jumped from 3.6 percent to 6.1 percent, they are still far less likely to receive a diagnosis than children from other racial groups. White children in the survey were diagnosed with ADHD at a 12 percent rate in 2016, up from 7.2 percent in 1997; 12.8 percent of African American children were diagnosed with ADHD in 2016, up from 4.7 percent in 1997.

The survey also found incidences of the disorder varied significantly by geography. Children in the Western region of the United States were less likely to be diagnosed with ADHD—7 percent in 2016—compared to the Northeast, Midwest, or South, all of which exceeded 10 percent. In 1997, 5 percent of children in the Western states were diagnosed with ADHD, while other regions ranged from 5.5 percent to 6.9 percent.

The NHIS survey did not attempt to find a cause for the increase, but the authors offered some possible factors, such as increased awareness of ADHD and a diminished social stigma for ADHD. Changes that expanded the definition of the disease also may have contributed to the increase.

The authors also say that previous studies also support a role of environmental risk factors, such as exposure to lead or certain pesticides or chemicals during pregnancy and the postnatal period, as well as nutritional deficiencies. Prenatal and perinatal risk factors, including pre-term birth, low birth weight, maternal cigarette smoking, and use of certain medications or illicit substances during pregnancy also have been associated with ADHD risk in previous studies.

The study, “Twenty-year trends in diagnosed attention deficit/hyperactivity disorder among US children and adolescents, 1997–2016,” was published in the Aug. 31 issue of JAMA Network Open. It was first-authored by Guifeng Xu in the UI College of Public Health and co-authored by Lane Strathearn of the UI Roy J. and Lucille A. Carver College of Medicine, Buyun Liu of the UI College of Public Health, and Binrang Yang of Shenzhen Children’s Hospital in China.

The study can be found online at http://jamanetwork.com/journals/jamanetworkopen/fullarticle/10.1001/jamanetworkopen.2018.1471

This story originally appeared in Iowa Now

Additional Media Coverage

ADHD numbers are rising, and scientists are trying to understand why (Washington Post)

About 10 percent of US children are diagnosed with ADHD (CNBC)

10% of US children diagnosed with ADHD, study finds (CNN)

Over Past 20 Years, The Percentage Of Children With ADHD Nearly Doubles (California Healthline)

ADHD Rates Rising Sharply in U.S. Kids (WebMD)

New study finds children’s ADHD diagnoses on the rise (CBS2Iowa)

Study links food allergy to autism spectrum disorder in children

A portrait of Assistant Professor Wei Bao of the Department of Epidemiology in the University of Iowa College of Public Health.
Wei Bao

A new study from the University of Iowa finds that children with autism spectrum disorder (ASD) are more than twice as likely to suffer from a food allergy than children who do not have ASD.

Wei Bao, assistant professor of epidemiology at the UI College of Public Health and the study’s corresponding author, says the finding adds to a growing body of research that suggests immunological dysfunction as a possible risk factor for the development of ASD.

“It is possible that the immunologic disruptions may have processes beginning early in life, which then influence brain development and social functioning, leading to the development of ASD,” says Bao.

The study analyzed the health information of nearly 200,000 children gathered by the U.S. National Health Interview Survey (NHIS), an annual survey of American households conducted by the U.S. Centers for Disease Control and Prevention. The children were between the ages of 3 and 17 and the data were gathered between 1997 and 2016.

The study found that 11.25 percent of children reportedly diagnosed with ASD have a food allergy, significantly higher than the 4.25 percent of children who are not diagnosed with ASD and have a food allergy.

Bao says his study could not determine the causality of this relationship given its observational nature. But previous studies have suggested possible links—increased production of antibodies, immune system overreactions causing impaired brain function, neurodevelopmental abnormalities, and alterations in the gut biome. He says those connections warrant further investigation.

“We don’t know which comes first, food allergy or ASD,” says Bao, adding that another longitudinal follow-up study of children since birth would be needed to establish temporality.

He says previous studies on the association of allergic conditions with ASD have focused mainly on respiratory allergy and skin allergy, and those studies have yielded inconsistent and inconclusive results. The new study found 18.73 percent of children with ASD suffered from respiratory allergies, whereas only 12.08 percent of children without ASD had such allergies, and 16.81 percent of children with ASD had skin allergies, well above the 9.84 percent of children without ASD.

“This indicates there could be a shared mechanism linking different types of allergic conditions to ASD,” says Bao.

Bao says the study is limited in that the NHIS depends on respondents to voluntarily self-report health conditions, so the number of children with ASD or allergies may be misreported by those taking the survey. But he says the large number of respondents and ethnic and gender cross-representation of the survey are major strengths.

The study, “Association of Food Allergy and Other Allergic Conditions with Autism Spectrum Disorder in Children,” was published online in the June 8 issue of JAMA Network Open. The first author is Guifeng Xu, PhD candidate in the UI College of Public Health and graduate research assistant in the UI Roy J. and Lucille A. Carver College of Medicine. Additional co-authors include Linda G. Snetselaar, professor of epidemiology in the UI College of Public Health; Jin Jing, professor of maternal and child health at the Sun Yat-Sen University in China; Buyun Liu, postdoctoral researcher in the UI College of Public Health; and Lane Strathearn, professor of pediatrics in the Carver College of Medicine.

This story originally appeared in Iowa Now

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UI analysis finds more children are diagnosed with autism than previously thought

The number of children in the United States diagnosed with autism spectrum disorder may be significantly higher than previously thought, according to a new University of Iowa analysis published in the Journal of the American Medical Association (JAMA).

A portrait of Assistant Professor Wei Bao of the Department of Epidemiology in the University of Iowa College of Public Health.
Wei Bao

The analysis of data from the U.S. Centers for Disease Control and Prevention (CDC) suggests that 2.4 percent of American children between the ages of 3 and 17—or 1 in 41—have been diagnosed with autism, higher than most earlier estimates of about 1.46 percent or 1 in 68 children. Wei Bao, assistant professor of epidemiology in the UI College of Public Health and corresponding author of the analysis, says the higher number shows the need for officials to think about reallocating health care resources to care for significantly more people with autism.

“Previous thinking about autism is that it is very rare, but this study tells us that it is no longer something that is very rare,” says Bao. “This should cause us to reconsider what our future priorities in research, service, and policy should be regarding children who have autism spectrum disorder. Clearly, we need more people to care for children with autism.”

The UI analysis used nationally representative data from the CDC’s National Health Interview Survey from 2014 to 2016, which collects data on a broad range of health topics through thousands of in-person household interviews each year. As part of the interview, CDC survey-takers ask respondents if the randomly sampled child living in the household has ever been diagnosed with autism.

Bao says the previous estimate of 1.46 percent was derived from the CDC’s Autism and Disabilities Monitoring Network (ADDM), which collects data from the health and special education records of 8-year-old children at 11 selected sites across the United States. The UI analysis was based on a nationally representative sample of children ages 3 to 17, and Bao cautions that these methodological differences in study design make direct comparisons between the two databases difficult.

The analysis also confirms earlier findings about gender and racial/ethnic disparity of autism in U.S. children, that it is much more frequent in boys (3.54 percent) than girls (1.22 percent), and less frequent in people of Hispanic origin (1.78 percent) than in non-Hispanic whites (2.71 percent) or non-Hispanic blacks (2.36 percent).

It found the highest prevalence of autism in Northeast states, at 3.05 percent. The Midwest was at 2.47 percent, the West at 2.24 percent, and the South at 2.21 percent. Bao speculates that rates are lower in the South and West because higher percentages of the population living in those states are Hispanic, a population that tends to have a lower prevalence of autism overall.

Bao says the limitation of the analysis is that the data is self-reported by the household respondent to the CDC survey-taker and is not subject to any third-party adjudication.

The analysis does not identify a cause for the increasing number of autism spectrum disorder cases. Bao says greater awareness among parents and health care providers might be the cause of some of the increase, but environmental and genetic factors likely are responsible for a large part of the gap. He points to previous studies—including one of his own—that show children are at greater risk of autism if their mothers have diabetes before or during pregnancy; since diabetes is often caused by obesity, the increase could be linked to the increasing weight of Americans.

“Autism is a highly complex disease caused by multiple genetic and environmental factors,” Bao says. “Maternal diabetes could be one of those factors, but it is not the only one. We need to find more about the underlying driving factors.”

The paper, “Prevalence of Autism Spectrum Disorder Among US Children and Adolescents, 2014–2016,” was published in the January 2018 issue of JAMA. Its first author is Guifeng Xu, PhD candidate in the UI College of Public Health and graduate research assistant in the UI Roy J. and Lucille A. Carver College of Medicine, and is co-authored by Buyun Liu, postdoctoral researcher in the College of Public Health, and Lane Strathearn, professor of pediatrics in the Carver College of Medicine.

This story originally appeared in Iowa Now.

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UI researchers conduct largest survey yet of PCBs in schools

An empty classroom.New research from the University of Iowa shows that polychlorinated biphenyls (PCBs), chemicals known to cause cancer in humans, are present in older schools and that the source of the PCBs is most likely outdated building materials, such as window caulking and light ballasts.

The multi-year study by the Iowa Superfund Research Program at the UI is the largest yet to examine airborne PCBs in schools. It shows that though the presence of PCBs can vary from school to school and even classroom to classroom, children’s exposure rates are roughly the same in rural and urban areas. It also shows that exposure to PCBs by inhalation may be equal to or higher than exposure through diet, a finding that surprised researchers.

Researchers collected indoor and outdoor air samples at six schools in Iowa and Indiana from 2012 to 2015. And though none of the schools had PCB levels high enough to meet federal standards for immediate remediation, researchers say the study is important because it shows that reduction of airborne PCBs in schools could be accomplished by removing old caulk around windows and modernizing light fixtures.

The study, published in Environmental Science & Technology, comes at a time of increasing concern over PCBs in schools. In 2014, a school in Lexington, Massachusetts, was shuttered after high levels of PCBs were found inside the building. New York City officials recently completed a multi-year program to replace PCB-laden light ballasts in more than 800 schools. And last year, parents in Malibu, California, won a publicized court battle to remove PCBs in schools.

“Due to the presence of PCBs in the environment, humans are easily exposed to them,” says Rachel F. Marek, assistant research scientist at the UI College of Engineering and lead author of the study. “Exposure of school-aged children to PCBs is of particular concern because these are compounds we know impair memory and learning and cause cancer in humans.”

Besides PCBs, researchers looked for the first time at OH-PCBs, chemical compounds similar to PCBs, in schools. Although there is still much to learn about OH-PCBs and their potential health risks, some scientists believe that OH-PCBs could be more toxic than PCBs.

PCBs are man-made chemical compounds that were used in industrial and commercial applications from 1929 to 1979, when they were banned. However, PCBs are still present in the environment, especially in areas with high concentrations of heavy industry and in buildings constructed in the ’50s, ’60s, and ’70s, when PCBs were used in various building materials. Many public schools were built with PCB-laced materials, and public health experts estimate that as many as 25,920 schools nationwide still have window caulking that contains the chemical compounds.

Schools are not required to measure PCBs; however, the United States Environmental Protection Agency provides guidelines for acceptable PCB levels. UI researchers studied PCB levels in four urban schools in East Chicago, Indiana, and two rural schools in Columbus Junction, Iowa. PCB levels inside the schools were below the current EPA action level of 500 nanograms per cubic meter, with a maximum reading of 194 ng/m3. The highest PCB levels were reported at two schools in East Chicago. Both were built before the PCB ban in 1979.

“Our nation’s schools must provide a safe and healthy environment for growing and learning,” says Peter S. Thorne, professor and head of occupational and environmental health in the UI College of Public Health and principal investigator of the study. “In addition to protecting children from risks such as asthma and obesity, schools need to be free of elevated exposures to persistent pollutants, including lead and PCBs.”

The exact level of PCB exposure at which harm is caused to children is unknown. This is a question that the Iowa Superfund Research Program is trying to answer through its research.

The four schools in East Chicago are not far from the Indiana Harbor and Ship Canal, an industrial waterway that is a known source of airborne PCBs. Researchers hypothesized that the schools’ proximity to the canal would influence PCB levels inside the schools. However, though indoor air samples from two of the schools resembled air samples collected near the canal, indoor air samples from the other two schools presented very different results, which researchers concluded were caused by the presence of PCBs typically linked to window caulking and light ballasts.

Tests of indoor and outdoor air at two schools in Columbus Junction, which has no known source of industry-related PCB contamination, presented further evidence of PCB contamination via old building materials. Paint pigments also were found to be a likely source of PCBs in the schools.

“This is the first time we’ve been able to pinpoint the source of PCBs inside schools,” says Keri C. Hornbuckle, professor of civil and environmental engineering at the UI College of Engineering and project leader for the Iowa Superfund Research Program. “This study shows that the indoor air is contaminated, and that contamination is due to materials that remain in use in the school buildings.”

UI researchers are planning their next PCB project, one that will measure PCB levels in different rooms in the same pre-1979 building. They also plan to offer free indoor PCB testing to schools.

“The results of our study are really quite chilling,” says Hornbuckle. “To put it simply, any school that hasn’t been remodeled since the 1970s may have high levels of PCBs in the air, which children breathe day in and day out.”

The Iowa Superfund Research Program (ISRP) at the University of Iowa studies the sources, exposures, and toxicities of PCBs in the environment. This program, which is funded by the National Institute of Environmental Health Sciences, brings together scientists with expertise in toxicology, engineering, microbiology, public health, and chemistry.

The goal of the Airborne Exposure to Semi-Volatile Organic Pollutants (AESOP) Study, part of ISRP, is to measure PCB exposure levels indoors and out and to track PCB exposure among 345 children and their mothers. The study, which began in 2006, already has provided new insight into airborne PCB exposure and challenged prevailing views on how humans are exposed to PCBs.
This story originally appeared in Iowa Now.

Additional Media Coverage

Study: Replace aging building materials in schools
Chicago Tribune

Four East Chicago schools Have PCB levels
The Times of Northwest Indiana

U of I study finds PCBs in Columbus Junction Schools
The Muscatine Journal

UI finds PCBs in schools 
Des Moines Business Record

Indoor air in schools could add to children’s exposure to PCBs