Age-related changes of serum bone alkaline phosphatase and cross-linked C-telopeptides of type I collagen and the relationship with bone mineral density in Chinese women

Abstract: Background: Previous studies have shown that bone turnover rate changes with age. At the same time, there is no definitive research regarding age-related changes of bone turnover level and its association with bone mineral density (BMD) in Chinese mainland women. Methods: In a cohort of 663 Chinese mainland women aged 20–70 years, serum bone alkaline phosphatase (BAP) and serum cross-linked C-telopeptides of type I collagen (sCTX) were measured to evaluate the state of bone formation and resorption, respectively. BMD was measured in the posteroanterior spine, supine lateral spine, hip and forearm using a dual-energy X-ray absorptiometry. Results: The cubic polynomial regression model best fit age-related changes in serum BAP (R 2 =0.398, p <0.001) and sCTX concentrations (R 2 =0.148, p <0.001) with largest R 2 from comparison 8 different regression models. Their values reached a minimal level in the 30–39 years age group, and increased dramatically in the 40–59 years groups. There was a decreasing trend of BAP in women >60 years. The levels of BAP and sCTX were inversely correlated to BMD in various skeletal regions over the entire population (r =−0.096 to −0.357, p <0.05). sCTX was a significant predictor of a T-score≤−2.5 of BMD in postmenopausal women with sCTX levels above mean+2 SD of women aged 30–39 years compared with other postmenopausal women, which indicated by odds ratios 1.9–3.7 (p <0.05) for various skeletal regions, especially for the lateral lumbar spine (2.2, p <0.01), Ward''s triangle (3.7, p <0.01), and ultradistal end of radius+ulna (2.8, p <0.001). Conclusions: Age-dependent serum BAP and sCTX were inversely correlated to BMD, and sCTX was a useful parameter for the prediction of a low T-score of BMD at skeletal sites with abundant cancellous bone in postmenopausal women. [Copyright &y& Elsevier]