| Following the increasing survival rate of premature infants over the past 30 years, metabolic bone disease of preterm infants has been taken into account gradually. Approximately 80% of fetal calcium and phosphorus is accumulated during the last trimester, as the whole body calcium increases from approximately 5g at 24 wks of gestation to approximately 30g at 40 wks of gestation. The peak accretion rate for bone occurs at approximately 35 wks of gestational age, when the calcium accretion rate and the phosphorus accretion rate are approximately 150mg/kg/d and 75mg/kg/d respectively. Metabolic bone disease is a common problem in preterm infant due to less accumulation of bone minerals intrauterine and more rapid growth. It gives rise to rickets, osteomalacia, and osteoporosis in affected infants, Mild cases may show only biochemical changes and severe cases may lead tofracture.There are many factors which affect bone mineralization in preterm infants, such as birth weight, gestational age, feeding, calcium and phosphorus and vitamin D intake, maternal factors, etc. Recently, several studies have demonstrated that physical activity increases bone density in children, adolescents, and adults, whereas inactivity results in bone resorption and decreased bone mineral density. In the meantime, quantitative ultrasound (QUS) measurement of bone speed of sound (SOS) was developed to assess bone strength in children and newborn (including premature infants.). An ultrasound bone sonometer measures the bone speed of sound to reflect the property of bone.Baby touch consisted of tactile stimulation of the body and passive movements of the limbs, which developed favorable effects. There was little research about baby touch on metabolic bone disease of premature infants. By measuring the changes of biochemical markers such as serum osteocalcin and bone alkaline phosphatase, urine deoxypyridinoline in preterm infants, and by measuring the changes of left tibial SOS, we try to explore the feature of preterm bone turnover, and the effect of touch on bone formation and bone resorption in preterm infants.Materials and MethodsFifty-five newborn infants were recruited from the department of neonatology, Children Hospital, Zhejiang University School of Medicine from April through October 2005. Forty preterm infants whose gestational age less than 35 weeks were divided into preterm touch group and preterm control group at random according to admission time. The preterm touch group consisted of 20 preterm infants (10 males , 10 females), with gestational age of 32.8+1.0 weeks , birth weight of 1912 + 260 gram . The preterm control group consisted of 20 preterm infants (9 males , 11 females), with gestational age of 32.8 +1.3 weeks , birth weight of 1950 + 300 gram . Fifteen term infants (7 males , 8 females), with gestational age of 39.1+ 1.3weeks , birth weight of 3006 + 356 gram, were recruited as compared with preterm infants . All cases were appropriate for gestational age.The blood samples were drawn by vein puncture at 7~8Am on day 3 after birth when their life signs are stable. In the meantime, urine samples were collected for measuring urine deoxypyridinoline and creatine. Serum concentration of OC, BALP and urine DPD were assayed by ELISA, urine concentration of creatine was measured by alkaline picric acid method. The left tibial SOS was measured on day 3.When the forty preterm infants reached 40 wks of gestational age, the second samples were collected and SOS was measured, too.Baby touch was provided to 20 infants (preterm touch group) for twice daily, 15-minute periods, which consisted of three standardized five-minute phases. Tactile stimulation was given during the first and third phases, and passive extension movements for the arms and legs were given during the middle phase.All of data were analyzed with SPSS 10.0. At first the mean ± SD of the data was calculated, then the Normality and the Homogeneity were tested, DPD was transformed to homogeneity distribution by log transform. One-Way ANOVA was used to determine difference among three groups. Independent-samples t test was used to determine difference between two groups. Paired-samples t test was used to determine difference in gestational age, birth weight, body length and head circumference between two groups. The lever of statistical significance was based on two-tailed statistics at lever ofp<0.05.ResultsOn day 3, serum OC in the two preterm groups was significantly lower than that in the term control infants (46.5 + 6.7 ng/ml and 44.8 ±5.7 ng/ml vs. 59.6+10.6 ng/ml, p<0.05), and positively related with gestational age and birth weight (r=0.46, p <0.05;r=0.47 , p <0.05), serum BALP and urine DPD (common logarithmic transformation) in the two preterm groups were significantly higher than those in the term control infants (100.2 + 24.3 U/L, 96.4+ 19.6 U/L, 2.029 + 0.076> 2.023 + 0.131 vs. 64.7+13.9 U/L, 1.870 + 0.071,/? <0.05) , and negatively related with gestational age and birth weight (r=-0.62, /?<0.05;r=-0.58, p <0.05;r=-0.47, p <0.05;r=-0.38, p <0.05;). SOS in the two preterm groups was significantly lower than that in the term control infants (3015 + 49 m/sec, 3016 + 26 m/sec vs. 3214 + 66 m/sec, p <0.05), and positively related with gestational age and birth weight (r=0.66, p <0.05;r=0.56, p <0.05). There were no significant differences between the preterm touch group and the preterm control group on serum OC, BALP, urine DPD and SOS.When the two preterm groups reached 40 wks of gestational age , serum OC in the preterm touch group was significantly higher than that in the preterm control group (57.5 + 7.7 ng/ml vs. 37.8 + 6.3 ng/ml, /=9.022, /?<0.05), serum BALP in the two groups increased significantly than those on day 3, and serum BALP in the preterm touch group was significantly lower than that in the preterm control group (116.1 + 15.1U/L vs. 134.7+14.9 U/L, r=3.933, p <0.05), Urine DPD in the two groups increased significantly than those on day 3, but there was no significant difference between the two groups(common logarithmic transformation: 2.373 + 0.077 vs. 2.365 + 0.082, t=Q290, p>0.05). SOS in the preterm touch group was significantly higher than that in the preterm control group (3016 + 69 m/sec vs. 2956 + 38 m/sec, 7=3.366, jo<0.05). There were no significant difference between the two groups on body length, head circumference, thoracic circumference and forearm length, while weight and tibial length in the preterm touch group was significantly higher than that in the preterm control group (7=2.05, p <0.05;7=3.38, p<0.05).Comparison between the term control group and the preterm touch group reached 40 wks of gestational age: serum OC had no significant difference between the preterm touch group and the term control group (57.5 + 7.7 ng/ml vs. 59.6+10.6 ng/ml, 7=0.705, p >0.05) , serum BALP and urine DPD in the preterm touch group were significantly higher than those in the term control group (7=5.806, p<0.05;7=13.694, /?<0.05), There were no significant differences between the two groups on body length, head circumference, thoracic circumference, forearm length, weight and tibial length, while SOS in the preterm touch groupwas significantly lower than that in the term control group (t=SA34, p <0.05).Conclusion1. Compared with terms, there is less bone formation and active bone resorption in preterms on early days after birth.2. Baby touch promotes greater gain in body weight in preterm infants.3. Baby touch attenuates the decrease in bone mineralization after birth in preterm infants, increases bone formation and enhances bone density. |
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