摘要：Objectives. We examined the relationship between timing of poverty and risk of first-incidence obesity from ages 3 to 15.5 years. Methods. We used the National Institute of Child Health and Human Development Study of Early Child Care and Youth Development (1991–2007) to study 1150 children with repeated measures of income, weight, and height from birth to 15.5 years in 10 US cities. Our dependent variable was the first incidence of obesity (body mass index ≥ 95th percentile). We measured poverty (income-to-needs ratio < 2) prior to age 2 years and a lagged, time-varying measure of poverty between ages 2 and 12 years. We estimated discrete-time hazard models of the relative risk of first transition to obesity. Results. Poverty prior to age 2 years was associated with risk of obesity by age 15.5 years in fully adjusted models. These associations did not vary by gender. Conclusions. Our findings suggest that there are enduring associations between early life poverty and adolescent obesity. This stage in the life course may serve as a critical period for both poverty and obesity prevention. There are significant socioeconomic disparities in rates of childhood and adolescent obesity, defined as a body mass index (BMI) at or above the 95th percentile, adjusted for age and gender. 1–3 Children of low socioeconomic status (SES) are 1.6 times more likely to be obese than high-SES children 4 and have steeper rates of increase in obesity. 5,6 Despite evidence that the prevalence of obesity has recently stabilized among children overall, it continues to increase among low-SES children. 2,5 The positive relationship between low SES and obesity is especially worrisome because of relatively high rates of childhood poverty that have only increased in the recent economic downturn. 7 One in 5 US children (16.4 million) now live in families with incomes below the federal poverty level. 8 To better understand the relationship between poverty and obesity, longitudinal studies of childhood poverty and its associations with obesity throughout childhood are needed. To develop effective policies preventing the incidence of child obesity, studies must also determine critical periods in childhood during which poverty may exert greater influence on the incidence of obesity. 9,10 Most studies demonstrating a link between SES and obesity, however, have used a cross-sectional study design. 1,5,6,11–16 Fewer studies address the issue of timing of childhood poverty (or other SES measures) and obesity incidence (or changes in BMI) later in life. 17–20 Moreover, these few studies omit key information on weight history 17,19 and SES prior to middle childhood (younger than 7 years) 18,19 or are based on non-US populations, 21 which precludes the study of early life associations between poverty and obesity, and limits generalizability to the United States. We used a comprehensive, community-based data set of US children followed from birth to about 15 years of age and for whom multiple measures of children’s SES, height, and weight were collected. Our objective was to examine critical periods in the relationship between poverty and the risk of the first incidence of obesity across the early life course.
