Serum osteocalcin in relation to calcaneal bone mineral density in elderly men and women: a 5-year follow-up.

A 5-year follow-up study investigated serum concentrations of total (tOC) and intact (iOC) osteocalcin in relation to calcaneal bone mineral density (BMD). The study comprised two cohorts, 75- and 80-year-olds, both resident in the city of Jyväskylä, Finland. Baseline OC and BMD were obtained for 161 men and 233 women, of whom 83 men and 189 women participated in follow-up bone measurements. The mean concentration of tOC increased from 9.6 +/- 4.3 to 13.2 +/- 8.5 microg/l (P = 0.001) in men and from 11.2 +/- 4.9 to 14.0 +/- 6.1 microg/l (P < 0.001) in women, whereas mean iOC decreased from 6.4 +/- 3.0 to 5.9 +/- 3.0 microg/l (P = 0.273) and from 7.7 +/- 3.7 to 6.9 +/- 3.4 microg/l (P = 0.021) in men and women, respectively. TOC and iOC levels correlated inversely with BMD and change in BMD in both sexes (r ranged from -0.223 to -0.422 and P = 0.048 < or = 0.001). When we divided the baseline tOC and iOC values into four quartiles, the decrease in BMD was significantly greater in the third tOC quartiles in women and in the fourth tOC and iOC quartiles in men when compared with the lower quartiles. During the 5-year period, 19 men and 59 women sustained at least one fracture. These individuals with fractures had significantly higher iOC values and tended to have higher tOC values compared with the nonfracture group at baseline (P = 0.038 and 0.087, respectively). Our results indicate that baseline serum tOC and iOC were associated with bone loss and predicted fracture in the two cohorts of independently living elderly men and women.