Characteristics Of Bone Mineral Density Changes And Influencing Factors In Middle School Students

Research purpose:By measuring the forearm and calcaneus density and morphological indexes,strength and quality,family social environment,etc.of middle school students,the characteristics and influence factors of bone mineral density changes of middle school students are analyzed to provide a basis for revealing the rules of bone development of middle school students.Research methods:Cross-sectional tests and questionnaires were conducted on903 secondary school students aged 12-16 with the consent of the parents and the school.The test indicators included height,weight,sitting height,waist circumference,grip strength,vertical jump,body composition,forearm Bone mineral density and calcaneus bone density;questionnaire surveys include family environment,dietary habits,exercise habits,family member fracture history.Results:（1）BMD of forearm BMD for middle school students aged 12-16 is0.303g/m² for boys,0.322g/m² for girls,and calcaneus ultrasound penetration speed（SOS）is 1542m/s for boys,1552m/s for girls,and forearm and calcaneus of girls The density was higher than that of boys（p<0.05）.Forearm BMD increased with age,male F_0.05（4,461）=39.8,p<0.05;female F_0.05（4,430）=39.1,p<0.05;calcaneus SOS With age,male F_0.05（4,458）=6.7,p<0.05;female F_0.05（4,426）=3.7,p<0.05.（2）In the age group of the study,the maximum annual increase in bone mineral density of forearm of both males and females appeared at the age of 15-16 years（0.054 g/m²and 0.066 g/m²）;It appeared at the ages of 14-15（12 m/s）and 13-14（12 m/s）.The maximum value of the annual increase in the load-bearing bone（calcaneus）of boys and girls was 1 or 2 years earlier than that of non-load-bearing bones（forearm bones）;T value of calcaneus bone density was better than T value of forearm bone density,t=63.0,p<0.05.（3）The negative correlation coefficients r of BMD and height and waist circumference are all-0.2,and the positive correlation coefficients of BMD and BMI,weight,sitting height index,muscle mass,strength and total exercise time are between 0.1-0.3,p<0.05;The positive correlation coefficient between SOS and muscle mass,fat mass,strength,and body fat rate is between 0.1-0.4,p<0.05.（4）The calcaneal bone density of middle school students who regularly participate in extracurricular activities is higher,χ²=7.442,P<0.01,but does not affect the BMD of the forearm;the total length of one week of exercise is positively correlated with the BMD of the forearm,r=0.156,P<0.01,no correlation with calcaneal SOS,r=0.054,P=0.453.（5）The calcaneal SOS of the students who took calcium tablets was higher,χ²=4.663,P=0.031,whether eating calcium tablets did not affect the forearm bone BMD,χ²=1.756,P=0.185.（6）Students with a history of fracture in their parents have a higher risk of fracture,χ²=12.695,P<0.01,OR=3.53;students’bone density Lower fracture risk is also higher OR_BMD=1.21,OR_SOS=1.44.（7）Regression analysis found that the biggest influential factor of forearm BMD（R²=0.36）in middle school students was age（Sdβ=0.41,P<0.01）,followed by gender（Sdβ=0.07,P<0.01）;The biggest influencing factor of calcaneus SOS（R²=0.09）in middle school students is muscle mass（Sdβ=0.50,P<0.01）,followed by height（Sdβ=-0.39,P<0.01）.Research conclusions:BMD of middle school students is higher than boys,and the increase of BMD of boys is greater than that of girls.The development of calcaneus is earlier than that of forearm,but the increase of BMD of forearm is greater than that of calcaneus.（2）Forearm bone and calcaneus bone density gradually increase with age;the developmental sensitivity period of forearm bone density of male and female students is 15-16 years old;the rapid phase of calcaneal development of boys is 14-15 years old,and girls are at 13-14 years old,girls are 1year earlier than boys;calcaneus is 1-2 years earlier than the sensitive period of forearm bone development.（3）Participating in extracurricular activities is beneficial to the calcaneus density of the students.（4）If the child’s bone density is low or their parents have a history of fracture,the child’s own risk of fracture will be higher.（5）Forearm bone density is mainly affected by the combination of age,muscle mass,BMI,height,grip strength,waist circumference,and gender;calcaneus bone density is mainly affected by the combination of muscle mass,height,gender,age,and BMI.