| [Background]Obesity has been becoming one of the serious global public health problems in the21st century. Obesity of children and adolescents in China is entering a period of high incidence rate. With the change of living environment following economic growth and urbanization, such as excessive energy intake, low level of physical activity and more sedentary lifestyle, prevalence of obesity also showed a clear increasing trend. The damages are far-reaching for obese children and adolescents, not only leading to physical and mental disorders and physiological dysfunction obstacle, affecting the ability to learn. It is more serious that the obesity of children and adolescents can be carried to adults, leading to high blood pressure, heart disease, diabetes and other chronic diseases, even long-term morbidity and early death. Overweight and obesity is one of the major risk factors for many chronic diseases. The obesity of children and adolescents has become the hidden danger of these diseases. We must attach importance to the problems caused by the obesity of children and adolescents.The pathogenesis of obesity may have a genetic and environmental basis. A lot of study results showed that the risk factors causing the obesity of children and adolescents were various and interrelated, mainly including heredity, birth weight, diet, physical exercise, parental behaviors and awareness, society and economy, mental and other factors. Obesity whose reasons are complex is the result of multifactorial, long-term effects. Genetic factors determine the obesity susceptibility for individuals and various environmental factors promote the occurrence of obesity. The study demonstrated that it was an obvious growth trajectory phenomenon for the incidence and development of obesity at each phase of the age from embryo to adulthood. To investigate these phenomena and their impact factors will help to provide a theoretical basis for the obesity prevention of children and adolescents and launch effective early intervention. It will be also a great significance in reducing obesity related diseases in adulthood and ensuring lifelong health.[Objective]This study intends to understand the situation and related risk factors about overweight and obesity of a birth cohort including high and normal birth weight babies in childhood and adolescence; To analyze the weight change trends from birth to childhood and adolescence; To explore the interaction of birth weight and lifestyle factors, the impact of parental overweight and obesity on offspring and familial clustering of overweight and obesity and related lifestyle factors.[Methods]Subjects were selected from a birth cohort who was born in1993-1995in Jiangyin city and two central districts (Huishan and Xishan) of Wuxi city, Jiangsu Province. Those with birth weight≥4000g were selected as exposed group and those with birth weight<4000g but≥2500g as non-exposed group. This was a historic cohort study design. The baseline data was from the database established in the early90s of the three areas for women’perinatal health caring. It included mother’s demographic characteristics, the status of health, the primary inspection for gestation and parturition, prenatal checkup, producing and perinatal inspection and so on. We started a follow-up visit for the subjects in childhood during October2005to October2006. Information was collected on individual growth situation, life styles, diet, exercises, family characteristic of the subjects and life styles of their parents and so on. Physical examinations included height, weight and blood pressure, etc. Based on the first visit, these subjects were followed up again from October2010to October2011during their adolescence. In addition to the one similar to the previous visit, the information collected in this time is more specific and detailed. The more information of the parents was collected. The data including height, weight and blood pressure and so on was also measured in this visit.The body mass index (BMI) was regarded as the outcome variable of this study. Overweight and obesity were diagnosed by the Chinese sex-and age-specific BMI reference range published by Working Group of Obesity in China (WGOC). Overweight and obese children were used as study group matched by subjects with the same sex and age as control group.All data was double entered into a database using Epidata3.1and analyzed by SPSS16.0and SAS9.2. Varied statistical methods including t-test, ANOVA,χ2test, rank sum test, Logistic regression model, factor analysis, correlation analysis, and GLMMs were used in the analysis.[Results]1. Description of the cohortThe cohort study started when the subjects were born. Through two follow-ups in childhood and adolescence,2236subjects were eligible into the analysis sample, including1108macrosomia and1128babies with normal birth weight. This population included1488boys, accounting for66.55%(737in exposed group,751in control group) and748girls, accounting for33.45%(371in exposed group,377in control group).2. Baseline survey resultsRisk factors for high birth weight included post-term pregnancy, maternal high BMI before pregnancy, more amount of increased weight of mother during pregnancy. Their odds ratios were2.31(95%CI:1.48,3.63),1.17(95%CI:1.07,1.27) and1.11(95%CI:1.08,1.14) respectively.3. The follow-up survey results during childhood2870subjects aged between10and13were actual followed up. The incidences of overweight and obesity were12.03%(boys were15.66%, girls were4.81%) and2.15%(boys were2.42%, girls were1.61%) respectively during childhood. The combined incidence of overweight and obesity is14.18%(boys were18.08%, girls were6.42%). The incidences of overweight and obesity were13.45%and2.80%in exposed group and those in non-exposed group were10.64%and1.51%.The combined incidence of overweight and obesity of the exposed group (16.25%) was much higher than that of the non-exposed group (12.15%)(P=0.003). Compared with the non-exposed group, the relative risks of overweight and obesity in the exposed group were1.26(95%CI:1.01,1.58) and1.86(95%CI:1.03,3.33) respectively. Their attributable risks were2.81%and1.29%respectively. The average BMIs were different among the different birth weight groups. The incidences of overweight and obesity increased with birth weight increasing (P <0.01).Factors associated with overweight and obesity of children:Logistic regression results showed that men (OR=2.06), high birth weight (OR=1.48), mother overweight and obesity (OR=2.22), artificial feeding in infancy (OR=2.80) and mixed feeding (OR-2.70), often eat fried foods (OR=1.41), often eat late supper (OR=4.59), much watching TV time (OR=1.37), higher income (OR=1.47) and father drinking (OR=1.34) were risk factors of overweight and obesity of children. More frequent milk consumption (OR=0.66) was a protective factor.4. The follow-up survey results during adolescence77.91%(2236) of targeted2870subjects aged between15and18were actually followed up. The incidences of overweight and obesity were9.35%(boys were10.28%, girls were7.49%) and1.83%(boys were2.09%, girls were1.34%) respectively. The combined incidence of overweight and obesity is11.18%(boys were12.37%, girls were8.83%). The incidences of overweight and obesity were11.73%and2.44%in exposed group and those in non-exposed group were7.00%and1.24%.The combined incidence of overweight and obesity of the exposed group (14.17%)was much higher than that of the non-exposed group (8.24%)(P<0.001). Compared with the non-exposed group, the relative risks of overweight and obesity in the exposed group were1.68(95%CI:1.28,2.19) and1.96(95%CI:1.04,3.72) respectively. Their attributable risks were4.73%and1.20%respectively. The average BMIs were different among the different birth weight groups. The incidences of overweight and obesity increased with birth weight increasing (P <0.05).Factors associated with overweight and obesity of adolescents:Logistic regression results showed that men (OR=1.43), high birth weight (OR=1.62), weight of both parents were abnormal (OR=2.56), weight of mother was abnormal (OR=1.87), weight of father was abnormal (OR=1.85), very full per meal (OR=1.45), faster speed of meal (OR=1.34), more duration of computer using (OR=1.40), average status of education of mother (OR=1.46), high status of education of mother (OR=2.01) were risk factors of overweight and obesity of adolescents. Much physical activity time (OR=0.69) and attitude of mother towards obesity (OR=0.65) were protective factors.Interaction between birth weight and lifestyle factors on overweight and obesity of adolescents:among all lifestyle factors collected, six common factors including protein foods, sedentary lifestyle, fruits and vegetables, physical exercise, eating habits and food preferences were extracted through factor analysis. Logistic regression analysis showed that there were multiplicative interaction between birth weight and protein foods, fruits and vegetables. Their relative excess risk of interaction between birth weight and protein foods, fruits and vegetables and food preferences were-1.65(95%CI:-3.29,-0.01),1.36(95%CI:0.37,2.36) and1.19(95%CI:0.14,2.23) respectively. It indicated that there were additive interactions between them. The attributable proportion of interaction were76.74%,55.06%and48.29%.5. The cohort analysis about overweight and obesity of children and adolescentsAmong all2236subjects,1108were macrosomia and1128were normal birth weight babies. There were317(14.18%) children who were overweight or obese in childhood and250(11.18%) adolescents who were overweight or obese in adolescence. For boys, there were49.53%macrosomia.18.08%were overweight or obese in childhood and12.37%in adolescence. For girls, there were49.60%macrosomia.6.42%were overweight or obese in childhood and8.82%in adolescence. It can be drawn from above that the combined incidence of overweight and obesity of boys decreased and that of girls increased from childhood to adolescence.The weight change trend analysis of the cohort members:there was interaction between gender and time. That meant the weight change trend of boys and girls were different with time. There was no interaction between birth weight and time which indicated that the effects of two factors were independent. From childhood to adolescence, generally, the improvement rate of the BMI classification was greater than the deterioration rate and the difference was statistically significant (P=0.003). The improvement rate of the BMI classification was greater than the deterioration rate in boys and the difference was statistically significant (P=0.004). The improvement rate of the BMI classification was greater than the deterioration rate in girls, but the difference was not statistically significant (P=0.286).6. Analysis of the affect of parents’overweight and obesity for childrenBased on parents’BMI status, in groups including both parents with normal weight, father with abnormal weight, mother with abnormal weight, both parents with abnormal weight, the incidences of overweight and obesity in their offsprings were12.01%,14.20%,15.94%,29.09%(childhood) and7.52%、13.34%、13.43%、16.67%(adolescence). They both showed an increasing trend.The result of multiple linear regression exploring the relationship between adolescents’BMI and their parents’overweight and obesity status showed partial regression coefficient of parents’overweight and obesity status is0.54(95%CI:0.37,0.71)). The result of Logistic regression exploring the relationship of overweight and obesity status between adolescents and their parents showed compared with parents with normal weights, the risks of overweight and obesity for children whose father with abnormal weight, mother with abnormal weight and parents with abnormal weights were1.73(95%CI:1.23,2.42),1.89(95%CI:1.18,3.02) and2.36(95%CI:1.49,3.73). By further exploring these association between different genders, it indicated for boys whose father or parents with abnormal weight, their risks of overweight and obesity were1.83(95%CI:1.24,2.71) and2.05(95%CI:1.17,3.61) but no this finding for those whose mother with abnormal weight; For girls whose mother or parents with abnormal weight, their risks of overweight and obesity were2.49(95%CI:1.09,5.68) and3.07(95%CI:1.36,6.92) but no this finding for those whose father with abnormal weight. It can conjectured from above that mother with abnormal might have bigger impact on their daughters while father might have bigger impact on their sons. Compared with children whose parents with normal weight, parents with abnormal weight would have bigger impact on daughter (OR=3.07) than son (OR=2.05).The correlation of adolescents and their parents on overweight and obesity and lifestyle factors and so on:there might exist positive correlation for the factors including BMI, BMI classification, drink, tea, eating fried food, very full per meal, speed of meal, attitude towards obesity, evaluation to children’s stature and whether children need lose weight between parents and their children.[Conclusions]1. The incidence of overweight of this cohort is higher. The combined incidence of overweight and obesity in childhood is higher than in adolescence. It is an important protective measure to control overweight developing to obesity. Childhood is a period with high incidence of overweight and obesity and it should be paid high attention.2. High birth weight has direct influence on overweight and obesity of children and adolescents. The primary prevention of obesity should start from fetus. Lifestyle factors might modify the relationship of birth weight and obesity. The children with high birth weight should be intervened as high risk population by changing their unhealthy life habits to reduce the risk of overweight and obesity.3. Parental overweight and obesity status is an independent risk factor of overweight and obesity children and adolescents and this association would be different by genders. Overweight and obesity and lifestyle in parents and children are associated. Therefore, family factors should be paid attention for prevention and intervention of obesity in children and adolescents. |
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