Prevalence of Chronic Illness in US Kids Has Increased

Fran Lowry

February 16, 2010

February 16, 2010 — The rate of chronic health conditions among children in the United States increased from 12.8% in 1994 to 26.6% in 2006, particularly for asthma, obesity, and behavior and learning problems, according to results of a new prospective study published in the February 17 issue of the Journal of the American Medical Association.

"Understanding prevalence and dynamics of chronic conditions on a national scale is important when designing health policy, making accurate clinical predictions, and targeting interventions to prevent chronic conditions," write Jeanne Van Cleave, MD, from MassGeneral Hospital for Children, Boston, Massachusetts, and colleagues.

Patterns of how these health conditions have changed have not been widely examined, the authors note. The aim of this study was to examine fluctuations in the prevalence of obesity and other chronic conditions over time.

The investigators used data from the National Longitudinal Survey of Youth-Child (NLSY) Cohort (1988 - 2006) to estimate changes in prevalence, incidence, and rates of remission of obesity, asthma, other physical conditions, and behavior and learning problems in 3 consecutive cohorts of children in the United States.

The children were 2 through 8 years old at the beginning of each study period, and each cohort was followed up for 6 years. Cohort 1, followed up from 1988 to 1994, consisted of 2337 children, cohort 2 consisted of 1759 children and was followed up from 1994 to 2000, and cohort 3 consisted of 905 children and was followed up from 2000 to 2006.

Health conditions were reported by the parents and included any condition that limited activities or schooling or required medicine, special equipment, or specialized health services and that lasted at least 12 months.

Prevalence Increased With Time

The investigators report that the prevalence of any chronic condition increased with subsequent cohorts. The baseline prevalence for cohort 1 was 11.2% (95% confidence interval [CI], 9.7% - 12.8%; P < .001), for cohort 2 it was 16.6% (95% CI, 14.6% - 18.8%), and for cohort 3 it was 25.2% (95% CI, 22.0% - 28.7%).

The end-study prevalence of any chronic health condition was 12.8% (95% CI, 11.2% - 14.5%) for cohort 1 in 1994, 25.1% (95% CI, 22.7% - 27.6%) for cohort 2 in 2000, and 26.6% (95% CI, 23.5% - 29.9%) for cohort 3 in 2006.

The investigators also report substantial turnover in chronic conditions. At the beginning of the study, 7.4% (95% CI, 6.5% - 8.3%) of children in all cohorts had a chronic condition that persisted to the end, 9.3% (95% CI, 8.3% - 10.3%) reported conditions at the beginning that resolved within 6 years, and 13.4% (95% CI, 12.3% - 14.6%) had new conditions that arose during the 6-year study period.

Cohort 3 had the highest prevalence of having a chronic condition at any time of the study period — 51.5% (95% CI, 47.3% - 55.0%) — and there were higher rates among boys (adjusted odds ratio [AOR], 1.24; 95% CI, 1.07 - 1.42), Hispanic children (AOR, 1.36; 95% CI, 1.11 - 1.67), and black children (AOR, 1.60; 95% CI, 1.35 - 1.90).

The authors cite limitations of their study, including that information about children's health was parent-reported and subject to recall bias. With the exception of obesity, the NLSY did not use objective criteria for diagnoses. Some children may have been overdiagnosed, they point out.

In their conclusion, the authors write that chronic conditions in childhood are common and dynamic. This emphasizes the benefits of continuous and comprehensive health services for all children "to adjust treatment of chronic conditions, promote remission, and prevent onset of new conditions. Further research should examine etiological differences between persistent and remitted cases."

Drawing Conclusions Not Easy

In an accompanying editorial, Neal Halfon, MD, MPH, from the David Geffen School of Medicine, University of California–Los Angeles, and Paul W. Newacheck, DrPH, from the University of California–San Francisco, write that making sense of these findings is not an easy task.

Better access to care and better tools to diagnose chronic conditions may have contributed to the upward trend in prevalence seen in this study, they point out. In addition, concepts of health and disease and definitions of chronic illness in children have also changed from earlier decades.

So has the "social ecology" of childhood, the editorialists suggest, citing exposure to higher levels of toxic stress, increasing rates of absent parents, more sedentary lifestyles, more television and multimedia use, and high-calorie, high-fat diets.

High-quality longitudinal data that can trace how health develops in childhood are needed, they write.

"Current longitudinal surveys, including the NLSY, collect minimal health data and even less information on the possible antecedents of health problems, complicating interpretation of findings such as those reported by Van Cleave et al. The soon-to-be-implemented National Children's Study could go a long way toward better describing the dynamics of childhood chronic conditions and the risk and protective factors that influence their emergence, duration, and resolution."

The study was supported by a Robert Wood Johnson Foundation Investigator Award in Health Policy Research grant, the Centers for Disease Control and Prevention, and the Maternal and Child Health Bureau. Dr. Van Cleave has disclosed no relevant financial relationships. Dr. Halfon has disclosed receiving support from the Maternal and Child Health Bureau of the Health Resource Services Administration. Dr. Newacheck has disclosed receiving support from the Maternal and Child Health Bureau of the Health Resource Services Administration and the National Institute for Dental and Craniofacial Research.

JAMA. 2010;303:623-630, 665-666.

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