Obesity and skill attainment in early childhood

Abstract

This paper investigates the association between obesity and skill attainment in early childhood (aged 2–3 years). Data from the German Socio-Economic Panel Study are used to estimate models of developmental functioning in four critical areas (verbal skills, activities of daily living, motor skills, and social skills) as a function of various measures of weight (including body mass index and obesity) controlling for a rich set of child, parent, and family characteristics. The findings indicate that, among boys, obesity is associated with reduced verbal skills, social skills, motor skills, and activities of daily living. Among girls, obesity is associated with reduced verbal skills. Further investigations show that the correlations exist even for those preschool children who spend no time in day care, which implies that the correlations cannot be due solely to discrimination by teachers, classmates, or day care providers.

Introduction

In developed countries, obesity tends to be associated with worse labor market outcomes; in particular, lower wages or earnings (Cawley, 2004, Cawley et al., 2005, Brunello and D’Hombres, 2007, Lundborg et al., 2007), less wealth (Zagorsky, 2005), and a lower probability of employment (Paraponaris et al., 2005, Lundborg et al., 2007, Morris, 2007, Burkhauser and Cawley, 2008). Several papers have found evidence that the relationship is causal (e.g. Cawley, 2004, Cawley et al., 2005, Morris, 2007).

Obesity may worsen labor market outcomes for several reasons, including discrimination by employers or lower productivity due to worse health. Another possibility is that childhood obesity, which is a strong predictor of adult obesity,² leads to less skill formation and therefore lower productivity in adulthood (Sabia, 2007, Lobstein et al., 2004). An obese child might attain fewer skills for several reasons; e.g. obesity-related illness may impair skill acquisition, there may be discrimination by teachers, day care providers, or classmates, or high-ability parents may be better producers of both skills and health in their children.

This paper tests whether childhood obesity is associated with lower skill attainment, at younger ages (2–3 years) than previously examined. This research question is timely because the prevalence of childhood obesity has risen rapidly in many countries (Lobstein et al., 2004, Kurth and Schaffrath Rosario, 2007, Ogden et al., 2002, WHO, 2005), which has led some to describe childhood obesity as a pandemic (Malecka-Tendera and Mazur, 2006, Kimm and Obarzanek, 2002). This research is also timely because it contributes to the growing literature on early-childhood health and skill formation (e.g. Heckman, 2008, Heckman, 2007, Cunha et al., 2005).

Previous studies of whether childhood overweight is associated with lower skill attainment have focused largely on children of elementary school age (Datar and Sturm, 2006; Cairney et al., 2005; Datar et al., 2004, Graf et al., 2004, Mo-Suwan et al., 1999) or those about to enter elementary school (Mond et al., 2007). To our knowledge, this is the first study of obesity and skill attainment to study children as young as 2–3 years old. Studying pre-school children is informative because if obesity is associated with skill attainment prior to school entry, it suggests that it cannot solely be due to discrimination by schoolteachers or classmates.

Several studies have examined how childhood obesity correlates with academic outcomes. A study of nationally representative U.S. data on kindergarten children found a negative correlation between overweight status and test scores on math and reading exams, but these differences tended to become insignificant after controlling for socioeconomic and behavioral characteristics (Datar et al., 2004). A study of children and adolescents in Thailand found that overweight was associated with significantly lower grade point average among young adolescents (grades 7–9) but not younger children (grades 3–6) (Mo-Suwan et al., 1999). A study of nationally representative Icelandic data of 14- and 15-year old schoolchildren found that body mass index (BMI) was significantly and negatively correlated with grades in three language classes and mathematics (Sigfusdottir et al., 2007). Among older youths (aged 14–17) in the U.S., a negative relationship between BMI and grade point average has been documented among white girls, but not nonwhite girls or males (Sabia, 2007). A large literature has documented discrimination against obese students by classmates, teachers, and administrators; see the reviews by Puhl and Latner (2006) and Puhl and Brownell (2001).

Other research has examined the relationship between childhood overweight and motor skills. A study of first-grade children in the Cologne region of Germany found that obesity was associated with impaired motor development for both boys and girls (Graf et al., 2004). A study of elementary school children aged 9–14 years in a city in Ontario, Canada found that Developmental Coordination Disorder is a risk factor for overweight and obesity for boys but not girls (Cairney et al., 2005). A study of children aged 4.4–8.6 years in Lower Bavaria in Germany found that obese male (but not obese female) children were more likely to have impaired gross motor skills (Mond et al., 2007).

This paper tests whether childhood obesity is associated with lower skill attainment on four dimensions: verbal skills, activities of daily living, motor skills, and social skills. To our knowledge, our sample of children is younger than that used in any previous study of this question. In contrast to previous studies based on German data (Graf et al., 2004, Mond et al., 2007), a nationally representative data set is used.