摘要：Objectives. We assessed whether cumulative risk exposure underlies the relation between early childhood poverty and body mass index (BMI) trajectories. Methods. We interviewed youths and their mothers in rural upstate New York (168 boys and 158 girls) from 1995 to 2006 when the youths were aged 9, 13, and 17 years. At each interview, we calculated their BMI-for-age percentile. Results. Early childhood poverty predicted BMI growth trajectories from ages 9 to 17 years (b = 3.64; SE = 1.39; P < .01). Early childhood poverty also predicted changes in cumulative risk (b = 0.31; SE = 0.08; P < .001). Cumulative risk, in turn, predicted BMI trajectories (b = 2.41; SE = 0.75; P < .01). Finally, after we controlled for cumulative risk, the effect of early childhood poverty on BMI trajectories was no longer significant, indicating that cumulative risk exposure mediated the relation between early childhood poverty and BMI trajectories (b = 2.01; SE = 0.94). Conclusions. We show for the first time that early childhood poverty leads to accelerated weight gain over the course of childhood into early adulthood. Cumulative risk exposure during childhood accounts for much of this accelerated weight gain. One of the most rapid and startling epidemics confronting contemporary society is obesity. The prevalence of overweight and obesity among US adults increased from 56% in 1988 to 1994 to 66.3% in 2003 to 2004. The rate of obesity alone rose from 22.9% to 32.2% among adults, 1 and the incidence of overweight among adolescents aged 12 to 19 years increased from 11% to 17% during the same period. 2 Obesity has been linked to elevated rates of diabetes, cancer, coronary heart disease, and other ailments. 3 Being obese in late adolescence is associated with an adult mortality risk comparable to heavy smoking (> 10 cigarettes/day), and being overweight in late adolescence is comparable to the adult mortality risk associated with light smoking (1–10 cigarettes/day). 4 Because of the obesity epidemic, future life expectancy in the United States may actually drop in this century for the first time ever. 5 An important predictor of adult obesity is early childhood socioeconomic disadvantage. 6 – 13 This longitudinal association is even more consistent than are concurrent associations of socioeconomic status (SES) and obesity in adulthood. 14 , 15 For example, Poulton et al. found that as childhood SES decreased, body mass index (BMI; defined as weight in kilograms divided by height in meters squared) and waist-to-hip ratio at age 26 years increased. 10 Eighty percent of women who grew up in low-SES households were overweight or obese in adulthood; only 40% of women raised in higher-SES households were subsequently overweight or obese. 16 The association between childhood poverty and later obesity has been documented in a variety of contexts. We assessed whether early childhood poverty leads to adult obesity because of cumulative risk exposure during childhood. We built on the childhood and obesity literature by using linear growth curve (LGC) modeling to examine whether individual life course trajectories in BMI are also affected by early childhood poverty. Risk factors associated with poverty, such as poor housing quality or family turmoil, often do not occur in isolation. Cumulative risk captures the extent of ecological covariation in risk exposures by generating an index that additively models exposure to multiple sources of risk. Across multiple physical and psychological health outcomes, cumulative risk exposure predicts morbidity significantly better than does exposure to any single risk factor. 17 , 18 Among adult women, less physical activity, greater likelihood of skipping breakfast, and inadequate sleep function as intervening variables between poverty and the likelihood of remaining obese. 19 We employed a life course approach to examine the relation between early childhood poverty and the trajectory of obesity as well as the potential mediating role of cumulative risk. We tested 4 hypotheses in longitudinal data collected at 3 time points. First, we hypothesized that early childhood poverty predicts a life course trajectory of elevated BMI into young adulthood. Specifically, we theorized that the greater the proportion of a child's life that is spent in poverty from birth to age 9 years, the more likely that child is to follow a trajectory toward obesity from childhood to early adulthood. Second, we hypothesized that early childhood poverty predicts cumulative risk exposure. Third, we examined how cumulative risk and obesity covary over time. We theorized that changes in cumulative risk predict changes in BMI over time. Finally, we hypothesized that the relation between early poverty and the BMI trajectory is mediated by cumulative risk exposure.
