Quantitative ultrasound measurements and vitamin D status in the assessment of hip fracture risk in a nationally representative population sample

Abstract

Adjusted for age, gender, height and weight, calcaneal quantitative ultrasound (QUS) and serum 25-hydroxyvitamin D (S-25(OH)D) proved to be significant predictors of hip fracture among subjects aged ≥50 years. Even if their contribution to the predictive power was modest, they may be useful in the assessment of hip fracture risk in the elderly. This study assessed calcaneal QUS measurements, S-25(OH)D and several other factors for the prediction of hip fracture risk in a nationally representative population sample. The study population consisted of 3,305 subjects (1,872 women), aged 50 years or over, who had participated in a comprehensive health survey. QUS measurements were made by means of the Hologic Sahara device. S-25(OH)D was measured by radioimmunoassay. Emerging cases of hip fracture were identified from the National Hospital Discharge Register. During a mean follow-up of 8.4 years, 95 subjects sustained a hip fracture. After adjusting for age, gender, height, weight and each other, a 1 standard deviation increment in the quantitative ultrasound index (QUI) (21.7) and in S-25(OH)D (17.5 nmol/L) reduced the risk of hip fracture by 40 % (hazard ratio [HR] = 0.60, 95 % confidence interval [CI] = 0.42-0.86) and by 31 % (HR = 0.69, 95 % CI = 0.55-0.87), respectively. The predictive power of a model including age, gender, height and weight was improved by about 8 % after the addition of QUI and S-25(OH)D. Among subjects aged 75 years or over, the corresponding improvement was about 130 %. QUI and S-25(OH)D were significant and independent predictors of hip fracture. However, their ability to increase the predictive power of a statistical model including readily available simple variables such as age, gender, height and weight was rather modest. Still, our findings suggest that QUI and S-25(OH)D may be of clinical use in the assessment of hip fracture risk particularly in the elderly.