Ultrasonic parameters of bone in young normals: effect of age and sex

This study was carried out in order to investigate the early effects of ageing on both broadband ultrasound attenuation and speed of sound through the os calcis. A total of 217 normal subjects, subdivided into 113 fertile women (age range 18-51 years, mean +/- 1 SD=29.4 +/- 8.4 years) and 104 age-matched men (age range 20-49 years, mean +/- 29.3 +/- 7.1 years), were investigated. Mean broadband ultrasound attenuation values in men (127.3 +/- 12.8 dB MHz-1) were significantly higher than those found in women (118.3 +/- 17.2, P < 0.001), whereas no significant differences were found as far as mean speed of sound values was concerned. Both broadband ultrasound attenuation (r = -0.196, P < 0.046) and speed of sound (r = -0.226, P < 0.02) values were inversely related to age in men; only a decrease of speed of sound values with age was noted in women (r = -0.400, P < 0.001). Finally, there was a very high significant correlation between broadband ultrasound attenuation and speed of sound values in men (r = 0.458, P < 0.001), but this was lacking in women. Admitting that the measurement of broadband ultrasound attenuation is influenced not only by bone density but also by trabecular quantity, spacing and orientation, our results seem to indicate that, even during adulthood, and well before the deleterious effects of oestrogen lack become apparent, structural properties of skeletal tissue in female subjects are disadvantageous with respect to those found in male subjects. Furthermore, while there is a progressive and balanced involvement of both the elastic (as reflected by speed of sound) and the structural properties of skeletal tissue of men, an uncoupling between the two is typical of women.