The association between overweight and obesity on bone mineral density in 12 to 15 years old adolescents in China.

ABSTRACT: Overweight/obesity can influence bone mineral accretion, but the conclusions are not consistent. We aimed to examine the association between bone mineral density (BMD) levels and body mass index (BMI) in 12 to 15 years old adolescents.We performed a cross-sectional study including 8365 adolescents. BMD was evaluated using a quantitative ultrasound device. Z scores for BMI were evaluated using World Health Organization references. Logistic regression models were performed to evaluate the association between BMD levels and BMI.Totally 1866 (22.3%) adolescents had low /reduced BMD, and boys had a higher rate than girls (72.6% vs 27.4%, P < .001). The rates of thinness, normal weight, overweight, and obesity were 2.8%, 57.1%, 22.3%, and 17.8%, respectively. The multivariable-adjusted (age, sex, systolic blood pressure, and height Z score) ORs (95% CIs) of low/reduced BMD associated with BMI groups (thinness, normal [reference], overweight, and obesity) were 0.59 (0.39-0.89), 1.00, 1.61 (1.41-1.84), and 1.98 (1.69-2.30), respectively (Ptrend < .001). This positive association existed in boys and girls though the differences were not significant between normal weight and thin girls. The multivariable-adjusted ORs for each 1-unit increase in BMI Z score were 1.36 (1.24-1.49) for girls, and 1.23 (1.16-1.30) for boys, and 1.26 (1.20-1.32) for all participants.We observed a positive association between BMI and low/reduced BMD in 12 to 15 years old adolescents. More attention should be paid on overweight and obese adolescents to reduce the risk of low BMD. Further studies are needed to explore the mechanisms of this association.

The impact of height on low/reduced bone mineral density in Chinese adolescents aged 12-14 years old: gender differences.

Low/reduced bone mineral density (BMD) is an important predictor of childhood fracture. In this article, we presented the prevalence of BMD in Chinese adolescents and, for the first time, demonstrated the gender disparities in the impact of height on BMD. PURPOSE: To analyze the gender disparities in the association of low/reduced BMD with height in Chinese adolescents at the stage of growth spurt. METHODS: A total of 8152 adolescents aged 12-14 years old were included based on a cross-sectional study in Tianjin, China. Height and weight were measured with standard equipment. BMD was measured using the method of quantitative ultrasound. Adolescents with Z ≤ - 2.0 or - 2.0 < Z ≤ - 1.0 were defined as "low BMD" or "reduced BMD". RESULTS: The total low/reduced BMD rate was 22.0% in Chinese adolescents aged 12-14 years old, and boys were more likely to have low/reduced BMD than girls (30.1% vs. 12.9%, P < 0.001). The rate of low/reduced BMD significantly increased with age in boys (Ptrend = 0.019), whereas decreased with age in girls (Ptrend = 0.018). We found significant interaction effect between gender and height standard deviation score (height-Z) in the association with low/reduced BMD (Pinteraction < 0.001). There was a positive association of height-Z among boys (OR = 1.30, 95%CI 1.21-1.39, P < 0.001), meanwhile low/reduced BMD was inversely associated with height-Z among girls (OR = 0.85, 95%CI 0.78-0.94, P < 0.001). CONCLUSIONS: Our study suggested strong gender disparities in the impact of height on BMD in Chinese adolescents aged 12-14 years old, where the association between low/reduced BMD and height was positive among boys but inverse among girls. The study provides evidence on the early prevention and the risk factor identification of low/reduced BMD and childhood fractures.