summer effects on body mass index (bmi) gain and growth patterns of american indian children from kindergarten to first grade a prospective study夏季影响体重指数(bmi)增益和增长模式的美国印第安孩子从幼儿园到一年级的前瞻性研究.pdf

Zhang et al. BMC Public Health 2011, 11:951 /1471-2458/11/951 RESEARCH ARTICLE Open Access Summer effects on body mass index (BMI) gain and growth patterns of American Indian children from kindergarten to first grade: a prospective study Jianduan Zhang 1,2*, John H Himes1†, Peter J Hannan1†, Chrisa Arcan1†, Mary Smyth1†, Bonnie Holy Rock1† and Mary Story1† Abstract Background: Overweight and obesity are highly prevalent among American Indian children, especially those living on reservations. There is little scientific evidence about the effects of summer vacation on obesity development in children. The purpose of this study was to investigate the effects of summer vacation between kindergarten and first grade on growth in height, weight, and body mass index (BMI) for a sample of American Indian children. Methods: Children had their height and weight measured in four rounds of data collection (yielded three intervals: kindergarten, summer vacation, and first grade) as part of a school-based obesity prevention trial (Bright Start) in a Northern Plains Indian Reservation. Demographic variables were collected at baseline from parent surveys. Growth velocities (Z-score units/year) for BMI, weight, and height were estimated and compared for each interval using generalized linear mixed models. Results: The children were taller and heavier than median of same age counterparts. Height Z-scores were positively associated with increasing weight status category. The mean weight velocity during summer was significantly less than during the school year. More rapid growth velocity in height during summer than during school year was observed. Obese children gained less adjusted-BMI in the first grade after gaining more than their counterparts during the previous two intervals. No statistically significant interval effects were f