Inadequate calcium intake is a significant determinant on generalised osteopenia in Hong Kong Chinese adolescents with idiopathic scoliosis.

Adolescent idiopathic scoliosis (AIS) is a serious 3-dimentional deformity of the spine affecting mostly girls. The prevalence rate is 3%-4% in Hong Kong. Generalised osteopenia are found in AIS patients. This study attempted to study whether low bone mineral density (BMD) is related to calcium intake in AIS. 582 AIS patients & 206 healthy controls aged 11-16 years were enrolled. Areal BMD (aBMD) and volumetric BMD (vBMD) were evaluated by DXA (Norland-XR-36) and pQCT (Densiscan-1000) respectively. Calcium and other nutrients intakes were assessed by a food-frequency method. The results showed that absolute calcium intake of the subjects were low (< 500 mg/d). Mean calcium intake of AIS girls was significantly higher than that of controls[(441 +/- 344) mg/d vs. (390 +/- 281) mg/d, P = 0.015]. BMD of AIS was significantly lower than that of controls at most skeletal sites from age 11-16 years (P < or = 0.05). The percentage difference in BMD increased with age between the AIS and control group. Furthermore, calcium intake was significantly correlated with BMD at most skeletal sites from age 15-16 years. However, this association was not found in the controls. Calcium intake was an independent determinant to predict variation of BMD after controlling for confounding variables in multivariate analysis. It is suggested that absolute calcium intake of AIS was low. BMD at various skeletal sites of the AIS was consistently lower than those of controls across different adolescent years, and that the correlation between calcium intake and BMD occurs only in AIS but not in healthy control girls implying the importance of calcium in bone mineral gain among the AIS, and it also reflected an abnormal mechanism of calcium homeostasis and bone turnover in AIS. Further calcium interventional study is warranted to confirm the effect of calcium on BMD acquisition in AIS.