Children’s health: highlights from research

In the United States, more children are becoming obese at younger ages than in the past.Credit: Dan Atkin/Alamy Stock Photo

Vitamin D deficiency linked to COVID-19

It has been proposed since the start of the COVID-19 pandemic that vitamin D might help to protect against infection and serious illness. The ‘sunshine vitamin’ is known to stimulate the production of antimicrobial peptides in the respiratory tract. But its impact has proved hard to quantify. A systematic review of half a dozen studies, performed by Komal Shah at the Indian Institute of Public Health in Gandhinagar and her colleagues, found that low levels of vitamin D were clearly associated with an increased risk of infection and poor outcomes in children with COVID-19. Almost half of the children with COVID-19 in the review sample had a vitamin D deficiency.

More than a dozen randomized clinical trials have been conducted on the therapeutic and prophylactic effects of vitamin D in people of various ages in several countries. The findings are highly variable, ranging from no impact at all to a strong protective effect. Researchers caution that if vitamin D does have an impact, it is getting harder to see against the backdrop of effective vaccines and treatments.

QJM 114, 447–453 (2021); Nature Rev. Immunol. 22, 529–530 (2022)

Obesity in the United States is expanding

The number of overweight children in the United States is rising. Solveig Cunningham, a public-health epidemiologist at Emory University in Atlanta, Georgia, and her colleagues examined levels of obesity in children aged between 5 and 11 over two time periods: 1998–2004, and 2010–16. The children were participants in the Early Childhood Longitudinal Study, a long-running US study of children’s development.

The researchers found that, despite continuing efforts by policymakers to fight unhealthy weight, young people born in the latter period had higher levels of obesity and more severe obesity, at younger ages, than those born 12 years earlier. Among children aged 5, obesity levels increased from 12% in 1998 to 15% in 2010; by age 11, obesity rates hit about 20% for both time periods. The researchers suggest that more studies into the social and biological sources of early-onset obesity should be focused on preschool children. They speculate that policies beyond the usual encouragements of exercise and good diet might be needed to change developing weight issues and behavioural habits early in these children’s lives.

Pediatrics 150, e2021053708 (2022)

Early births raise risk of ADHD

A study of attention-deficit hyperactivity disorder (ADHD) adds further weight to the recommendation that elective deliveries of babies shouldn’t be scheduled before 39 weeks of gestation, because those few extra days or weeks can be crucial for fetal development.

ADHD affects around 10% of schoolchildren in the United States. Research has previously shown that children born before 37 weeks tend to have higher levels of ADHD. Nancy Reichman, a health economist at the Rutgers Robert Wood Johnson Medical School in New Brunswick, New Jersey, and her colleagues looked at the incidence of ADHD in children born in the later window of 37 to 41 weeks.

The team examined data from 1,400 children in the Fragile Families and Child Wellbeing Study, a US birth-cohort study that analysed children born at 75 hospitals in 20 large US cities between 1998 and 2000. When the children were 9 years old, the team of researchers interviewed their teachers to get a good sense of the kids’ attention levels in a classroom setting. They found that children born at 37–38 weeks gestation had on average 17% higher ADHD scores than did children born at 39–41 weeks.

The American College of Obstetricians and Gynecologists already recommends that elective deliveries shouldn’t be performed before 39 weeks, yet more than 10% of them still are in the United States, Reichman says. The study adds another reason to push for later elective procedures, and suggests that ADHD screening would be useful for children who are born before 39 weeks.

J. Pediatr. https://doi.org/gqnfjm (2022)

US child suicide on the rise

Suicide is one of the 10 most common causes of death in children aged 12 and younger in the United States, and the numbers of suicides are rising. James Price, a professor emeritus of Health Education and Public Health at the University of Toledo, Ohio, and Jagdish Khubchandani, a public-health researcher, at New Mexico State University, in Las Cruces, analysed suicides in the United States from 2010 to 2019. They say that suicide rates in children under 12 increased by 138% on average over this period. Girls were particularly vulnerable — rates increased by 300% in girls, compared with 95% in boys. Rates went up by 95% for Black children and 158% for white children.

Previous studies have similarly noted alarming rises in child suicides in the United States. The causes of these high rates are not precisely known, but they include mood disorders, exposure to trauma and access to firearms.

National statistics show that the overall suicide rate in the United States declined slightly in 2019, and this continued into the pandemic: suicide rates were 3% lower in 2020 than in 2019. But Marie-Laure Charpignon, who is studying social and engineering systems and statistics at the Massachusetts Institute of Technology in Cambridge, and her colleagues reported that although total suicide-related deaths in the United States declined during this period, the same is not true among adolescents. From 2019 to 2020, on average, rates of suicide among those aged 10–19 increased across the team’s sample of 14 states.

In 2021, the American Academy of Pediatrics, along with other hospital and psychiatry associations, declared a national emergency in child and adolescent mental health, asking for more funding for mental-health screening and care.

J. Community Health 47, 232–236 (2022); JAMA Pediatr. 176, 724–726 (2022)

Cannabis conveyed by breastfeeding

The use of marijuana has risen to about 4–6% among pregnant and breastfeeding women in the United States, despite general medical advice to avoid cannabis during these times. The Academy of Breastfeeding Medicine based in Chicago, Illinois, for example, recommends against the use of marijuana while breastfeeding.

Surveys have found that nearly 70% of pregnant women think that the occasional use of marijuana is generally safe during pregnancy. A study by Michael Moss, a toxicologist at the University of Utah in Salt Lake City, and his colleagues adds some much-needed data to the topic. They looked at 20 well-educated, breastfeeding mothers in Oregon who used cannabis medicinally on a daily basis. The team found that more than half increased their cannabis use after birth, perhaps to battle lack of sleep or anxiety. The study showed that chemicals found in cannabis — tetrahydrocannabinol (THC) and cannabidiol (CBD) — accumulated in breast milk, resulting in an average infant THC dose of 4.1 micrograms per kilogram per day. There are no generally accepted guidelines for a safe limit of THC in any age group. Given that both cannabinoids were clearly present in the breast milk and are known to affect the brain, the authors argue that research on the health and neurodevelopmental impacts on infants exposed to these compounds is urgently needed.

Pediatr. Res. 90, 861–868 (2021)

Genetic factors in sudden infant deaths

Incidents of sudden infant death syndrome (SIDS, sometimes called cot death) have declined in wealthy countries over the past few decades, but the syndrome still takes the lives of 0.1–0.8 infants per 1,000 births, making it one of the leading causes of infant death. There are many well-known risk factors for SIDS, including babies sleeping on their front, overheating and maternal smoking during pregnancy. And previous studies found pathogenic variants in a set of 200 cardiac genes in up to 30% of SIDS cases, suggesting a genetic role in SIDS relating to the heart’s function.

Cordula Haas, a geneticist at the University of Zurich, Switzerland, and Jörg Thomas, an anaesthesiologist at the University Children’s Hospital Zurich, and their colleagues investigated the genes involved in the control of breathing, such as those that encode the chemoreceptors and ion channels responsible for detecting low levels of oxygen. The team screened data from 155 children who died of SIDS and found that 5 had potentially pathogenic variants in a set of 11 genes known to be involved in ventilatory control.

The authors conclude that respiratory-related genetic variants might be factors (but probably not the sole cause of death) in a minority of SIDS cases. This discovery could help to untangle the possible genetic causes of this devastating syndrome.

Pediatr. Res. 92, 1026–1033 (2022)

Leukaemia genes tracked

More than 90% of children with acute lymphoblastic leukaemia (ALL), the most common form of childhood cancer, survive, but the condition remains a leading cause of death from disease in young people. For those who do not respond well to treatment, a new genetic map of the condition might point the way to better outcomes.

Charles Mullighan, a cancer researcher at St. Jude Children’s Research Hospital in Memphis, Tennessee, and his colleagues sequenced the genomes of 2,754 children with ALL. The researchers identified 376 significantly mutated genes that might drive the development of cancer, 70 of which had never before been implicated in ALL. Each child had fewer than ten mutations, which Mullighan says should help to enable precise tracking of the disease and the design of targeted therapies.

Nature Genet. 54, 1376–1389 (2022)