EFFECT OF BONE-DENSITY OF THE HEAD ON TOTAL-BODY DEXA MEASUREMENTS IN100 HEALTHY SWEDISH WOMEN

Purpose: The aims of this study were to examine the bone areal density of the head and how it varied in relation to the density of the rest of the skeleton, and with age, and body mass index (BMI). Our intentio n was to study the feasibility of excluding the head from the rest of the body, a method which might improve the fracture prediction power o f bone mineral measurements. Material and Methods. Bone mineral per ar ea (BMA) and bone mineral content (BMC) (g) were determined in 100 con secutive female volunteers, aged 17 to 78 years, with total and partia l body measurements. Results: BMC of the head was found to be 20.2 +/- 2.2% of that for the total body. The BMA of the head was 2.38 +/- 0.2 1 times higher than that of the rest of the body. The correlation betw een the BMA of the head and the rest of the body was significant (r=0. 73). The average change in z-score (referred to the same age group in our material) was 0.20 when the head was excluded from total body BMA. The BMA of a) total body, b) total body, head excluded, and c) head d ecreased with age. The BMA of the head was correlated to BMI in the ol der age groups (p<0.01). The relative statistical uncertainty for repe ated measurement of head BMA was 1.8%. Conclusion: The change of the b one density of the head with age and BMI, in comparison to that of the rest of the skeleton, suggests that when the head is excluded from to tal body BMA better predictive value for fracture risk is obtained.