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

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 fort-nation 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. (c) 2005 Elsevier B.V. All rights reserved.