Osteocalcin and frailty among older women

Abstract

<h3>Background</h3><p>Osteocalcin is a bone-specific protein involving many physiological processes, primarily bone turnover. Also closely related to the musculoskeletal system is the frailty syndrome.</p><h3>Aim</h3><p>To investigate if circulating osteocalcin levels and frailty are associated in the old, and in addition, if the presumed association is mediated through alterations in bone.</p><h3>Methods</h3><p>999 community-dwelling women from the OPRA (Osteoporosis Prospective Risk Assessment) cohort, all aged 75 years. Serum total osteocalcin was measured together with bone turnover markers PINP and CTX. An OPRA-adapted frailty index was applied. Association between osteocalcin and frailty was investigated using both logistic regression (osteocalcin quintiles Q_low-Q_high; Q₁-Q₅) and linear regression. Splines model was added. Association between osteocalcin level and individual components of the frailty index were investigated using Kruskal-Wallis or Chi² test.</p><h3>Results</h3><p>Low osteocalcin (Q₁) was associated with being frail (frailty prevalence 36% vs. 23% (Q1 vs. Q5); absolute difference 13%) in both unadjusted (OR_unadj 1.82, 95% CI[1.12-3.00]) and adjusted analyses (OR_adj 2.55, 95% CI[1.46–4.44]); even after adjustment for bone turnover markers, s-PINP and s-CTX (2.50, 95% CI[1.11–5.61]). Women with low serum osteocalcin (Q1) had significantly poorer gait function (gait speed (<em>p</em> = 0.001; p for trend < 0.001), more steps taken (<em>p</em> = 0.003; p for trend 0.004)), higher inflammation (<em>p</em> < 0.001; p for trend < 0.001), and a larger proportion had diabetes (p for trend < 0.001) and polypharmacy (p for trend < 0.001), compared to those with highest osteocalcin levels (Q5).</p><h3>Conclusion</h3><p>Low osteocalcin in circulation was associated with being frail, also after adjusting for bone turnover markers.</p>