Serum undercarboxylated osteocalcin is a marker of the risk of hip fracture: A three year follow-up study

We have previously shown that elderly women with an increased serum undercarboxylated osteocalcin (ucOC) level have an increased risk of sustaining a hip fracture as compared to those with normal serum ucOC. We reassessed our findings on a larger number of hip fractures that occurred over 3 years in 183 institutionalized women (aged 70–97 years) belonging to a large prospective clinical trial. Total OC, carboxylated OC, ucOC, and alkaline phosphatase were significantly higher at baseline in those who sustained a hip fracture during the follow-up. The age-adjusted odds ratio for hip fracture was three times higher in women with increased ucOC at baseline (odds RATIO = 3.1, 99.9% C.I. = 1.7–6.0, p< 0.001). In the logistic regression, ucOC was still predictive of the hip fracture when age and parathyroid hormone concentration were included into the model (odds RATIO = 2.6, 95 % C.I. = 1.05–6.4). These data confirm that ucOC is a marker of the increased risk of hip fracture in elderly institutionalized women. Serum ucOC may reflect some nutritional deficiency associated with increased bone fragility.