US White and Black Women Do Not Represent the Bone Mineral Density of Sub-Saharan Black Women

Reference populations from the United States (US) are often used around the world for representative measures of bone mineral density (BMD) by sex, age, and race. We examined BMD in adult black Zimbabwean women and compared it to that of US women (white and black). In a cross-sectional study, we recruited healthy black Zimbabwean women working at Parirenyatwa Hospital regardless of designation, who were not pregnant and had no diseases or medications known to affect BMD. Dual-energy X-ray absorptiometry scans of the left hip and lumbar spine (L1-L4) were performed for each participant by 1 operator, on 1 dual-energy X-ray absorptiometry machine. Results are presented for 289 participants aged 20-69 years, with a mean weight, height, and body mass index (BMI) of 71.7 ± 15.1 cm, 164.9 ± 6.3 kg, and 26.3 ± 5.3 kg/m2, respectively. At 5% level of significance, age and BMD were weakly associated for the total lumbar spine (p ≤ 0.001) but not for the total hip (p = 0.890) and femur neck (p = 0.062). BMI and weight were positively correlated with BMD for all 3 sites (p ≤ 0.001). Compared to US white women, mean BMD for black Zimbabwean women in this study was 4.5%-7.4% lower for the lumbar spine but 2.0%-4.8% higher for the total hip and 0.2%-10.2% higher for the femur neck for 20-59 years. Compared to US black women, mean BMD for black Zimbabwean women was 9.1%-11.5% lower for the lumbar spine and 1.4%-8.1% lower for the total hip for 20-59 years. Black Zimbabwean women also had lower mean weight and BMI per decade age group as compared to US women. Differences in weight and BMI offer a possible explanation for the differences in BMD between black Zimbabwean women and US white and black women. Including adjustments for body frame when calculating Z-scores may accurately reflect BMD.