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

BackgroundPrevious 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.MethodsIn 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.ResultsThe cubic polynomial regression model best fit age-related changes in serum BAP (R2 = 0.398, p < 0.001) and sCTX concentrations (R2 = 0.148, p < 0.001) with largest R2 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).ConclusionsAge-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.