| Objectives:To investigate the current situation of bone mineral density（BMD）among children and adolescents aged 7～17 years old in Guangzhou,and to analyze the influencing factors with insufficient bone mineral density of total body less head（TBLH BMD）and lumbar spine（LS BMD）,thus to provide a scientific basis for promoting bone health as well as preventing and treating osteoporosis in adulthood.Methods:In this cross-sectional study,a total of 1990 students which aged7～17 years old from a middle school and a primary school in a district of Guangzhou was selected in April and May 2019.Dual energy X-ray absorptiometry was used to test students’BMD and questionnaire was made to collect information on environmental factors（family,birth and feeding,diet,sleep,screen and exercise）.1902 subjects with complete data of BMD test and questionnaire were finally included in this study.The growth curves of TBLH BMD and LS BMD were fitted by using lambda-mu-sigma（LMS）and the Z score was calculated for the BMD development evaluation（Z score≥-1 was regarded as normal BMD,and Z score<-1 was regarded as insufficient BMD）.Gender and age characteristics of BMD of each part were analyzed and further analyzed the changes of TBLH/LS BMD and its Z score as well as deficiency rate with age,distribution of various environmental factors by gender.The quantitative data consistent with normal distribution were described by mean±standard deviation,the t-test and variance analysis were used to compared the difference between gender and age,the correlation between age and BMD was analyzed by Pearson correlation coefficient.The qualitative data were described using frequency and percentage,χ2 test was used to compared difference by gender,Univariate logistic regression model was used to explore the relationship between age and insufficient of TBLH BMD and LS BMD.Univariate and Multivariate logistic regression models were used to analyze the influencing factors of TBLH BMD and LS BMD deficiency.The statistical analysis software is SAS9.4 and R 4.0.3,and the drawing software is Origin 2019 and Graph Pad Prism 8.3.0.Results:1.Bone mineral density status:（1）The average BMD of each part of 1902 subjects can be ranked from small to large as follows:left rib（0.51g/cm2）,right rib（0.53g/cm2）,left arm（0.58g/cm2）,right arm（0.61g/cm2）,thoracic vertebrae（0.65g/cm2）,total body less head（0.77g/cm2）,lumbar spine（0.82g/cm2）,left leg（0.89g/cm2）,right leg（0.92g/cm2）,Pelvis（0.94g/cm2）and head（1.27g/cm2）.There were differences in gender and age（P<0.001）.（2）The TBLH BMD of boys was higher than that of girls（P<0.001）.“Two crossings”around the age of 10 and 13 was occurred and this phenomenon could also be found in each percentile of the growth curve.（3）The LS BMD of girls was higher than that of boys in all age groups（except 7 years old,16 years old and 17years old）（P<0.05）.Except for P90 and P95（the LS BMD of boys was equal or higher than that of girls at the age of 16 and 17）,the LS BMD of girls was higher than that of boys in all percentiles.（4）There was no statistical difference in the distribution of Z score of TBLH BMD and LS BMD between age and gender.（5）The rate of TBLH BMD deficiency was 16.30%,17.08%for boys and 15.40%for girls.The LS BMD deficiency rate was 15.62%,15.80%for boys and 15.40%for girls.There was no significant difference in the rate of TBLH BMD and LS BMD deficiency.（P>0.05）.2.The distribution of environmental factors:（1）The educational level of students’parents is mainly in senior high school and above（83.61%and 68.78%respectively）,and the annual family income is mainly 100000 yuan and above（66.01%）.Most of the students were full-term（87.95%）.88.60%of the students had normal birth weight,and the proportion of high birth weight of boys（8.55%）was higher than that of girls（4.45%）.In the 6 months after birth,non-breastfeeding was dominant（58.65%）.Except for birth weight,there was no significant difference between gender（P>0.05）.（2）78.97%of the students ate breakfast 6～7times/week,and that of boys（81.51%）was higher than that of girls（76.03%）（P>0.004）.54.94%and 33.35%of the subjects ate coarse/fine grain and meat≥7times/week,respectively and boys were higher than girls（P<0.001）.28.56%and 20.05%of the students could eat vegetables and fruits every day and there was no gender difference（P>0.05）.The proportion of students consuming aquatic products,beans and nuts≥3times/week was 38.09%,34.41%and 19.43%respectively,and that of boys was higher than that of girls（P<0.05）.58.43%of the students consumed eggs≥3times/week,there was no gender difference（P>0.05）.37.53%of the students ate snacks≥3times/week,and girls（41.37%）were more than boys（34.19%）（P<0.05）.62.35%and 79.00%of the students consumed sugary drinks and dairy products≥2times/week,and the proportion of girls consuming≥5times/week was lower than that of boys（P<0.05）.（3）29.55%of the students had sleep deprivation,and the rate of sleep deprivation of boys was higher than that of girls（P<0.001）.The proportion of students with screen time≥1h/days was36.28%,and there was no gender difference（P>0.001）.53.48%of the students participated in extracurricular sports,and the proportion of boys was higher than that of girls（P<0.001）.3.Analysis of the influencing factors of TBLH BMD:（1）The results of Univariate logistic regression analysis showed that the father had undergraduate education or above（OR:0.33,95%CI:0.16～0.65）,and the higher the mother’s education（senior high school and junior college:OR:0.69,95%CI:0.48～1.00;Bachelor degree or above:OR:0.51,95%CI:0.26～0.99）,family income 200000 yuan or more（OR:0.45,95%CI:0.27～0.76）,meat intake frequency≥7times/week（OR:0.60,95%CI:0.42～0.86）,egg intake≥3times/week（OR:0.66,95%CI:0.48～0.92）,milk and dairy products≥5times/week（OR:0.65,95%CI:0.43～0.98）,participation in extracurricular exercise（OR:0.71,95%CI:0.52～0.99）was a protective factor for insufficient TBLH BMD in boys（P<0.05）.Intake of vegetables≥7times/week（OR:0.64,95%CI:0.41～1.00）,eggs≥3times/week（OR:0.65,95%CI:0.45～0.93）,and the higher the intake frequency of milk and dairy products（2～4times/week:OR:0.47,95%CI:0.30,～0.73;≥5times/week:OR:0.38,95%CI:0.24～0.60）was the protective factor of insufficient TBLH BMD in girls（P<0.05）.（2）The Multivariate logistic regression model showed that the father’s education level（aOR:0.42,95%CI:0.18～0.97）and meat intake≥7times/week（aOR:0.62,95%CI:0.42～0.92）were still the protective factors for TBLH BMD in boys（P<0.05）.The higher frequency intake of milk and dairy products（2～4times/week:OR:0.48,95%CI:0.31～0.75;≥5times/week:aOR:0.41,95%CI:0.26～0.65）of girls,the lower the risk of insufficient TBLH BMD（P<0.05）.4.Analysis of influencing factors of LS BMD:（1）The results of Univariate logistic regression analysis showed that parents’education level was undergraduate or above（Father:OR:0.51,95%CI:0.26～0.98;Mother:OR:046,95%CI:0.22～0.98）,annual family income 200000 yuan or more（OR:0.42,95%CI:0.23～0.76）is the protective factor of insufficient LS BMD in boys（P<0.05）;the high father’s education level（senior high school and junior college:OR:0.63,95%CI:0.41～0.95;bachelor degree or above:OR:0.34,95%CI:0.17～0.69）,fruit intake≥7times/week（OR:0.49,95%CI:0.29～0.84）and dairy products intake≥5times/week（OR:0.56,95%CI:0.35～0.90）were protective factors for LS BMD in girls（P<0.05）,while coarse/fine grain intake was≥7times/week（OR:1.45,95%CI:1.00～2.11）was a risk factor for insufficient LS BMD（P<0.05）.（2）The Multivariate logistic regression model showed that the father had bachelor degree or above（aOR:0.39,95%CI:0.19～0.79）and high intake frequency of milk and dairy products（aOR:0.55,95%CI:0.33～0.90）was still a protective factor for LS BMD deficiency in girls（P<0.05）,while coarse/fine grain intake frequency≥7times/week（aOR:1.67,95%CI:1.12～2.51）was a risk factor for LS BMD deficiency in girls（P<0.05）.Conclusions1.The BMD in different parts of children and adolescents have gender and age differences.The TBLH BMD of boys and girls have the phenomenon of“two crossings”around the age of 10 and 13,but not in LS BMD.2.The detection rate of TBLH BMD and LS BMD deficiency was high,and there was no difference between gender and age.3.Father’s high education level and daily meat intake contribute to the development of of boy’s TBLH BMD;high intake frequency of milk and dairy products is conducive to the growth of girl’s TBLH BMD.High educational level of father and high frequency of dairy intake can promote LS BMD development in girls,while high intake frequency of coarse/fine grain were not conducive to the growth of LS BMD.4.No correlation was found between sleep time,screen time,extracurricular exercise and TBLH BMD/LS BMD. |
