Associations between frailty and serum N-terminal propeptide of type I procollagen and 25-hydroxyvitamin D in older Spanish women: The Toledo Study for Healthy Aging.

Frail older people are at high risk for fractures and falls increasing the rates of institutionalization and mortality. Bone markers have been related to both aging and fractures. However, no previous reports have shown a potential relationship between serum bone markers such as N-terminal propeptide of type I procollagen (PINP), C-terminal telopeptide of type I collagen (β-CTX) and parathyroid hormone (PTH) with frailty in elderly female populations. This study is aimed at examining the associations of bone metabolism markers and frailty in older Spanish women through a descriptive cross-sectional analysis based on a cohort of the Toledo Study for Healthy Aging (TSHA). The levels of serum PINP, β-CTX, PTH and 25-hydroxyvitamin D (25(OH)D) were assessed in 592 participants (median age 74years) who were defined as robust, prefrail and frail according to Fried's approach. Frail subjects had significantly high levels of PINP, β-CTX and PTH and low production of 25(OH)D. After adjustment for confounders, high PINP levels (defined by the upper quartile) and low levels of 25(OH)D (lower quartile) remained significantly associated to frailty [OR for PINP: 2.19 (95% CI, 1.15-4.18; P=0.017); OR for 25(OH)D: 1.65 (95% CI, 1.02-2.67; P=0.042)]. Women with both high PINP levels and low 25(OH)D levels presented a 5.85-fold increased frailty risk (95% CI, 1.64-20.93; P=0.007). The main contribution of this paper is the novel definition of PINP and 25(OH)D markers as potential biomarkers of frailty and targets for intervention.