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

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. Introduction 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. Methods 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. Results 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 %. Conclusions 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.