Body mass index, calcium intake, and physical activity affect calcaneal ultrasound in healthy Greek males in an age-dependent and parameter-specific manner

Quantitative ultrasound (QUS) is a peripheral bone densitometry technique that is rapidly gaining in popularity for the assessment of skeletal status. This study was carried out to examine the effect of anthropometric, dietary, physical activity, and other lifestyle factors on QUS parameters in healthy Greek males of various ages, including children (n = 192), adults (n = 106), and elderly (n = 86) subjects. Calcaneal QUS measurements were performed with the Sahara device (Hologic), which measures broadband ultrasound attenuation (BUA) and speed of sound (SOS) through the os calcis. A composite parameter, the quantitative ultrasound index (QUI), and an estimate of heel bone mineral density (eBMD) were also derived. BUA correlated positively with height, weight, and body mass index, as well as waist and hip circumferences (P < 0.001), but this was not the case for SOS. QUI and eBMD were inconsistently related with anthropometric characteristics. Overweight and obese males had significantly higher BUA than normal-weight subjects (P < 0.05), but similar SOS, QUI, and eBMD; this held true for all age groups. Boys participating in organized physical activities had significantly higher SOS, QUI, and eBMD than those who did not (P < 0.05), although BUA was similar in the two groups; no differences according to organized physical activity were detected in adults and the elderly. On the other hand, adult men devoting at least some time to non-organized physical activities had significantly higher QUS values than their non-exercising peers (P < 0.05); no such effects, however, were seen in children and the elderly. Adult men with calcium intakes above 800 mg/day had significantly higher SOS, QUI, and eBMD than those consuming less calcium (P < 0.05), and also tended towards higher BUA (P = 0.079); no such differences were observed among children and elderly men. The effects of physical activity and calcium intake on heel QUS persisted even after controlling for body size. Overall, body weight was the sole significant positive determinant of BUA (beta = 0.373; t = 6.589; P < 0.001), explaining approximately 14% of the total variance, while age was the sole significant negative determinant of SOS (beta = -0.198; t = -3.321; P = 0.001), albeit explaining only less than 4% of the total variance. In conclusion, body size, dietary calcium intake, and physical activity patterns seem to inconsistently and age-dependently influence heel QUS among healthy Greek males in a parameter-specific manner.