Factors influencing calcaneus quantitative ultrasound measurements in an urban population.

OBJECTIVE To estimate the effect of demographic, social, behavioural and anthropometric factors on quantitative ultrasound (QUS) parameters in an urban population. METHODS Cross-sectional evaluation of consecutive subjects selected as part of the EPIPorto study, Portugal. Information was obtained on demographic, social, clinical and behavioural characteristics using a standard protocol. Calcaneus QUS parameters (Broadband Ultrasound Attenuation-BUA, and Speed of Sound-SOS) were obtained for men and women, stratified by age group. Comparisons according to exposure levels were made using the Kruskal-Wallis test and the multivariate effect on QUS parameters was estimated by linear regression. RESULTS 1482 consecutive subjects (1010 females and 472 males), aged from 18 to 92 years. Higher levels of QUS parameters were found in the younger groups and progressive decrease with age were reported. Men showed higher values as compared to women in all parameters and differences between them increased with age. Differences were significant for BUA after the age of 39 and for SOS after the age of 59. In women, the multivariate model showed that age, body mass index (BMI) and smoking status were independent predictors of BUA and SOS. In men, age, BMI and calcium intake were significantly associated with BUA and SOS. CONCLUSION The reference values in our Portuguese population are similar to others obtained in Southern European countries. In the Portuguese population, QUS parameters have age, sex and BMI as its major determinants. In addition, BUA and SOS may reflect specific bone characteristics influenced by a different set of independent determinants.