Pediatricians have long known that children with Down syndrome grow differently than typical children, but the last growth charts for children with Down syndrome were developed almost 30 years ago. Since that time, clinical care for children with Down syndrome, especially early in life, has changed enormously, and their life expectancy has increased from 35 years in 1985 to 53 years in 2007.
It was clear to researchers at The Children’s Hospital of Philadelphia and the Centers for Disease Control (CDC) that the growth charts available for children with Down syndrome no longer measured up.
In 2009, they launched the Down Syndrome Growing Up Study (DSGS), funded by a four-year, $1.2 million grant from the CDC. The goal was to gather information about contemporary growth patterns of children with Down syndrome so that pediatricians and parents could see where a child’s height and weight stood relative to their genetic potential.
Using highly trained people to do the growth measurements, the study team led by Babette Zemel, PhD, director of the Nutrition and Growth Laboratory at CHOP, followed 637 participants, up to age 20, from January 2010 to July 2013. About 80 percent of the participants were recruited from the Trisomy 21 Program at CHOP and from community locations in the greater Philadelphia area.
“The families and the kids were so enthusiastic and appreciative that we were doing this project,” Dr. Zemel said. “They knew that there was a problem with the growth charts for children with Down Syndrome, and they really wanted to be a part of fixing it. The Trisomy 21 Program, led by Mary Pipan, MD, was superb to work with. ”
While checking a child’s height and weight may seem like an ordinary task, asking hundreds of children with Down syndrome to take their shoes off is far from routine. Down syndrome, a multisystem genetic disorder resulting from an extra copy of chromosome 21, occurs in about one in 700 U.S. births. Medical complications that accompany the condition affect every aspect of children’s daily lives, including eating, sleeping, hearing, talking, moving, and learning.
“Rather than using growth measurements that were acquired in the clinic, which are sometimes done under hurried circumstances, we were able to do it in a research setting so that we could take our time and make sure the children were comfortable and got used to the idea,” Dr. Zemel said. “We had a picture book to show and explain to them how we would take growth measurements so that they could anticipate what we were going to do. We had good participation and very accurate measurements.”
Results from the study appeared online Oct. 26 in Pediatrics. Dr. Zemel’s co-authors were Dr. Pipan, Virginia A. Stallings, MD; Waynitra Hall, MS; Kim Schadt, MSN; all from CHOP; and David S. Freedman, PhD, and Phoebe Thorpe, MD, MPH, both of the CDC.
One of the major study findings is that infants with Down syndrome are growing much better than they were several decades ago. Children under age 3 showed marked improvements in weight gain compared to the 1988 U.S. growth charts for children with Down syndrome. Improvements in height, reflecting taller stature, occurred mainly in males aged 2 to 20, relative to the earlier charts. In general, the DSGS charts were consistent with charts from children with Down syndrome in the United Kingdome, published in 2002.
The DSGS team also created the first-ever body mass index (BMI) charts for children with Down syndrome. The researchers noted that the charts do not represent an ideal distribution of BMI, but only describe BMI distribution among their study participants. They added that further investigations should determine how to use the BMI charts to screen patients for excess body fat and associated health symptoms.
While clinicians and researchers realize that obesity is a problem for children with Down syndrome, especially as they move into their teenage years and beyond, an interesting finding from the study that Dr. Zemel pointed out is that the weight charts for children with Down syndrome did not change much over the past few decades.
“This is quite surprising, given that for the rest of the U.S. population, there has been an increase in the prevalence of obesity,” said Dr. Zemel, who also is on the faculty of the Perelman School of Medicine at the University of Pennsylvania.
Another research project led by Andrea Kelly, MD, at CHOP and Sheela Magge, MD, MSCE, at Children’s National Medical Center is focusing on any health consequences of excess weight in teens with Down syndrome. They will determine if being overweight or obese carries the same cardiometabolic risks as it does for typical children, and they also will assess study participants’ body image and quality of life.
For more information on the DSGS study, visit here.