| ObjectivesTo explore BMI growth trajectories in 0-3-year-old infants and to clarify the association between different BMI growth trajectories and obesity and body composition in 6-year-old children.MethodsBased on the Ma’anshan Birth Cohort（MABC）,3,474 pregnant women who were eligible for inclusion from May 2013 to September 2014 were enrolled in this study.During the physical examination of pregnant women in the early,middle and late stages of pregnancy,the maternal relevant information were collected,The data on childbirth was abstracted from delivery records.At the age of 3,6,9,12,18,24,30,36 and 72 months,the doctors measured and recorded the height（length）and weight of the children in the cohort,meanwhile,obtained feeding informaton by questionnaire and at the age of six,the body composition analyzer was used to measure human body composition.Of the 3,273 infants who had single live birth,those with serious birth defects,premature,low birth weight,fetal macrosomia,or post-term of gestation were excluded and those with Insufficient anthropometric measurements were excluded,Finally,2442 infants were eligible for our analysis According to the WHO standards in2007,and the six years old children were divided into four groups: underweight,normal weight,overweight and obesity.The body composition variables（skeletal muscle,body composition and body fat percentile）were divided into three groups: low level group（<25th percentile）,medium level group（25th～75th percentile）and high level group（>75th percentile）.Growth mixture modeling（GMM）was applied to identify homogeneous subgroups of BMI-trajectory in infants for the first three years of lifeand multinomial Logistic regression models were used to analyze the association between BMI growth trajectory and obesity and body composition in six years old children.ResultsAccording to the results of the model,the BMI growth trajectory is classified into four categories: “normal with slowly declining growth pattern,” comprised 53.4% of infant BMIz values,“delayed with persistently accelerating growth pattern” comprised9.5% of infants,“accelerating with subsequent slightly declining growth pattern”comprised 15.6% of infants and “Accelerating first and then declining growth pattern”.14.7% of 6-year-old children are overweight（boys 16.3% and girls 13.10%）and 8.5%are obese（boys 12.7% and girls 4.1%）.At the age of 6,1064 children were in the middle level of skeletal muscle（boys 551 and girls 513）,and the body fat was in the middle level（boys 494 and girls 487）.After adjustied confounding factors,children in the delayed with persistently accelerating growth pattern were more likely to be obese at the age of 6 than those in the normal with slowly declining growth pattern（OR=20.38,95%CI:12.49～33.25）,and the skeletal muscle of the children was less ikely to be in the low level group at the age of 6（OR=0.37,95%CI:0.20～0.69）.The risk in the high level group was 3.77 times higher than that in the control group（P<0.001）.Similar results could be found in the association between the trajectory and body fat and body fat percentile.The Accelerating first and then declining growth pattern was the protective factor of low skeletal muscle and body fat in children at the age of 6 years（OR=0.66,95%CI:0.47～0.93;OR=0.70,95%CI:0.54～0.92）.The possibility of obesity at 6 years old in children with accelerating with subsequent slightly declining growth pattern was 8.33 times higher than that in children with normal with slowly declining growth pattern（P<0.001）,and the risk of skeletal muscle at high level at 6 years old in this group was 2.07 times higher than that in the control group（P<0.001）.ConclusionThe BMI growth trajectory of full-term normal birth weight infants at 0-3 years old can be divided into four growth patterns: “normal with slowly declining growth pattern”,“delayed with persistently accelerating growth pattern”,“accelerating with subsequent slightly declining growth pattern” and “Accelerating first and then declining growth pattern”.Taking the normal with slowly declining growth pattern as the control group,the children in the delayed with persistently accelerating growth and accelerating with subsequent slightly declining growth pattern had a higher risk of overweight and obesity at the age of 6.The accelerating with subsequent slightly declining growth pattern was a risk factor for the group with high skeletal muscle content,but there was no significant correlation with body fat and body fat percentile.The accelerating first and then declining growth pattern was the protective factor for the low content of skeletal muscle and body fat in 6-year-old children. |
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