Franchetti Yoko, Ide Hiroo
Research Division of Health Policy in Aging Society, Chiba University Hospital, Inohana 1-8-1, Chuo-ku, Chiba-shi, Chiba, Japan.
BMC Public Health. 2014 Apr 9;14:334. doi: 10.1186/1471-2458-14-334.
It is unknown whether childhood physical development in Asian populations differs from western populations, since no longitudinal analysis has been performed in Asian countries yet. Utilizing the 21st Century Longitudinal Survey in Newborns, we studied the timing of adiposity rebound (AR) among Japanese children and determined whether AR occurs earlier in obese children compared to nonobese children. Furthermore, we identified important demographic, social, and lifestyle factors that affect their physical development.
We used data from the annual surveillance of Japanese children born in 2001, with 45,392 eligible subjects. We applied survival analysis to evaluate the AR and a trajectory method for the BMI transition across 5 ½ years. Time-dependent and time-independent factors affecting BMI changes were investigated using longitudinal analysis. Accounting for the known difference in prevalence between Japanese and Western children, we adopted a 95th percentile of BMI as criterion for obesity.
Mean BMI at birth and at ages 1 ½, 2 ½, 3 ½, 4 ½, and 5 ½ years for all subjects were 12.6, 16.3, 16.1, 15.8, 15.5, and 15.4, respectively, showing a progressive reduction after 1 ½ years. However, among obese children at 5 ½ years, 39.6% had experienced AR as early as at age 4 ½ years. Controlling for sex, Cox's proportional hazards model showed that obese children had a 48.5% higher hazard to experience AR than nonobese children. The difference in BMI transition between obese and non-obese children was also captured by a trajectory method. In longitudinal analysis, BMI was lower for children who had a longer gestational period whereas children who received parental care from non-family members gained higher BMI values.
With the 95th percentile cutoff for children obesity, obese Japanese children developed AR earlier than nonobese Japanese children, similar to those in Western countries reported in the literature. Primary caretakers and length of gestational period were the most important socio-demographic factors affecting physical development.
由于尚未在亚洲国家进行纵向分析，亚洲人群儿童期身体发育是否与西方人群不同尚不清楚。利用21世纪新生儿纵向调查，我们研究了日本儿童肥胖反弹（AR）的时间，并确定肥胖儿童的AR是否比非肥胖儿童更早出现。此外，我们确定了影响其身体发育的重要人口统计学、社会和生活方式因素。
我们使用了对2001年出生的日本儿童进行年度监测的数据，有45392名符合条件的受试者。我们应用生存分析来评估AR，并采用轨迹法分析5.5年期间的BMI变化。使用纵向分析研究影响BMI变化的时间依赖性和非时间依赖性因素。考虑到日本和西方儿童在患病率上的已知差异，我们采用BMI的第95百分位数作为肥胖标准。
所有受试者出生时以及1.5岁、2.5岁、3.5岁、4.5岁和5.5岁时的平均BMI分别为12.6、16.3、16.1、15.8、15.5和15.4，显示出1.5岁后逐渐下降。然而，在5.5岁的肥胖儿童中，39.6%早在4.5岁时就经历了AR。在控制性别后，Cox比例风险模型显示肥胖儿童经历AR的风险比非肥胖儿童高48.5%。轨迹法也捕捉到了肥胖和非肥胖儿童在BMI变化上的差异。在纵向分析中，孕期较长的儿童BMI较低，而接受非家庭成员照料的儿童BMI值较高。
以儿童肥胖的第95百分位数为界，肥胖的日本儿童比非肥胖的日本儿童更早出现AR，这与文献中报道的西方国家情况相似。主要照料者和孕期长短是影响身体发育的最重要社会人口学因素。
