Analyzing Screening Policies for Childhood Obesity

Abstract

Due to the health and economic costs of childhood obesity, coupled with studies suggesting the benefits of comprehensive (dietary, physical activity and behavioral counseling) intervention, the United States Preventive Services Task Force recently recommended childhood screening and intervention for obesity beginning at age six. Using a longitudinal data set consisting of the body mass index of 3164 children up to age 18 and another longitudinal data set containing the body mass index at ages 18 and 40 and the presence or absence of disease (hypertension and diabetes) at age 40 for 747 people, we formulate and numerically solve - separately for boys and girls - a dynamic programming problem for the optimal biennial (i.e., at ages 2, 4, …, 16) obesity screening thresholds. Unlike most screening problem formulations, we take a societal viewpoint, where the state of the system at each age is the population-wide probability density function of the body mass index. Compared to the biennial version of the task force's recommendation, the screening thresholds derived from the dynamic program achieve a relative reduction in disease prevalence of 3% at the same screening (and treatment) cost, or - due to the flatness of the disease vs. screening tradeoff curve - achieves the same disease prevalence at a 28% relative reduction in cost. Compared to the task force's policy, which uses the 95^th percentile of body mass index (from cross-sectional growth charts tabulated by the Centers for Disease Control and Prevention) as the screening threshold for each age, the dynamic programming policy treats mostly 16 year olds (including many who are not obese) and very few males under 14 years old. While our results suggest that adult hypertension and diabetes are minimized by focusing childhood obesity screening and treatment on older adolescents, the shortcomings in the available data and the narrowness of the medical outcomes considered prevent us from making a recommendation about childhood obesity screening policies.

Figure 1

Tradeoff curves of disease prevalence at age 40 vs. treatment prevalence (equation (3)) for the optimal three-age screening policy for ages (12,14,16) and the optimal two-age screening policy for ages (14,16) from Fig. 7 of the Electronic Companion. The x denotes the biennial version of the USPSTF recommendation. (a) hypertension among males; (b) diabetes among males; (c) hypertension among females; and (d) diabetes among females.

Figure 2

Optimal screening thresholds for the three-age screening policy at ages (12,14,16), expressed as the percentile of the gender- and age-based BMI distributions tabulated by the CDC (Kuczmarski et al. 2000), for two cases: the treatment prevalence equals that of the biennial USPSTF policy (— for males and -x- for females) and the disease prevalence equals that of the biennial USPSTF policy (⋯ for males and ·x· for females). The biennial USPSTF policy uses the 95^th percentile for ages 6,8,…,16.