Chronic health conditions were found in 12.8% of children studied in 1994, compared with 26.6% of another group of same-aged children studied in 2006, the researchers found.
''We knew before we started this study that childhood chronic diseases were generally on the rise," says study researcher Jeanne Van Cleave, MD, a pediatrician at Mass General Hospital for Children and an instructor of pediatrics at Harvard Medical School in Boston.
"But this study really gives a better picture," she tells WebMD. That's partly because the researchers were able to study three groups of children over time to better figure out what was happening.
As bleak as the findings may sound, Van Cleave tells WebMD she sees a bright spot: ''The most important finding is that a lot of children will have chronic conditions during childhood, but a lot of these conditions will go away, will resolve over time."
The study findings are published in TheJournal of the American Medical Association.
Tracking Childhood Chronic Disease
Van Cleave's team looked at four types of health conditions, as reported by parents:
- Obesity, using the accepted definition of a body mass index at or above the 95th percentile for age and sex
- Other physical conditions, such as hearing or vision difficulties, allergies, or chronic ear infections
- Behavior or learning problems such as hyperactivity, emotional disturbances, or attention deficit disorder.
To be considered chronic, the condition had to limit activities or schooling or require medicine, special equipment, or special health services, and had to last at least 12 months.
The data was retrieved from the National Longitudinal Survey of Youth-Child Cohort. Children were ages 2 through 8 at the beginning of each study period. Each group was followed up for six years -- from 1988 to 1994, 1994 to 2000, and 2000 to 2006.
Group one had 2,337 participants, group two had 1,759, and group three included 905.
Chronic conditions increased with each group, with group three having the highest percent of children with chronic conditions both at the start and end of the study period.
''For each of those three groups, the rate of having a chronic condition during the study increased by about 10% for each subsequent group," Van Cleave says.
The chances of having a chronic condition during any part of the six-year study was greatest for the third group, with 51.5% of them affected at some time (and more than half of that 51% having obesity), Van Cleve says. Rates were higher among boys and Hispanic and black children. Older children were more likely than younger children to have a chronic health conditions, she found.
Some children did outgrow the problems, however. When Van Cleave combined all three groups, she found that 9.3% of the children who had a chronic condition at the start of the study did not have it at the end. "Chronic conditions during childhood do not appear to be as permanent as once thought," she tells WebMD.
The study was funded and supported by the Robert Wood Johnson Foundation, the CDC, and the Maternal and Child Health Bureau of the U.S. Health Resources Services Administration.
The study findings, while not surprising, are of concern, says Geetha Raghuveer, MD, associate professor of cardiology at the University of Missouri-Kansas City School of Medicine and pediatric cardiologist at Children's Mercy Hospital in Kansas City, Mo., who reviewed the study findings for WebMD.
''I was taken away by one comment in the paper that at least one in two children in the recent [group] had some sort of chronic condition," she says. "And that's a lot."
"Many of these problems are lifestyle-related," she says, citing the high percent of obesity found in the children.
"Parents can make small changes in their child's diet and see a big improvement in overall health," she says. "It can be as simple as taking liquid calories out of your child's diet. That may be all that's necessary to prevent excess weight gain and all the problems."
The study findings are of concern, agrees Neal Halfon, MD, MPH, University of California, Los Angeles professor of pediatrics, health sciences, and policy studies, who also directs the UCLA Center for Healthier Children, Families and Communities. "It shows that over that time period that the rates are going up quite significantly," says Halfon, who co-wrote an editorial that accompanies the study. He reports receiving support from the Maternal and Child Health Bureau.
''I was surprised at the magnitude of the increase, but I wasn't surprised at the overall trend," he says, ''because that trend has been emerging for the past 30 or 40 years."
Part of the increase, he tells WebMD, can be attributed to the generally broader definition of childhood health problems. But not all, he says, blaming ''the social environment and social ecology of childhood" for some of the increase in chronic health conditions such as obesity. For instance, he says, higher-calorie foods and an increase in ''screen time" with excess television and computer use contribute to the obesity epidemic.
Halfon suspects there may be common pathways for some of the conditions, as some children have multiple conditions. "The good news here is, it's really shining a light on a problem that we have that in a sense we have been ignoring," he says.