Bone mineral density reference values in Singaporean adults and comparisons for osteoporosis establishment – The Yishun Study

BACKGROUND: While there have been studies in Singapore on the prevalence and economic burden of osteoporotic hip fracture, there is a severe lack of reference data on bone mineral density and prevalence of osteoporosis. The purpose of this study is to establish the reference values for BMD and compare prevalence of osteoporotic conditions using other available reference values so as to better understand the status of bone health in Singaporean adults. METHODS: We carried out a population-based cross-sectional study using dual-energy x-ray absorptiometry (Hologic Discovery Wi) to measure the bone mineral density of Singaporean adults aged ≥21 years. A total of 542 participants were recruited from the large north-eastern residential town of Yishun. We computed T- scores (denoted by T(SG)) for each individual in the study. Similar diagnoses were also done based on T-scores provided by the densitometer (T(DXA)), NHANES database (T(NHANES)), and China (T(CHN)), and the differences in prevalence compared. We then compared the concordance between T(SG) and T(DXA) in the classification of osteoporosis. Osteoporosis was defined according to criteria by the World Health Organization (WHO). RESULTS: Peak lumbar spine BMD was 1.093 ± 0.168 g/cm(2) in women, and 1.041 ± 0.098 g/cm(2) for men. Peak whole-body BMD was 1.193 ± 0.93 g/cm(2) in women at, and 1.224 ± 0.112 g/cm(2) for men. Prevalence of osteoporosis based on lumbar spine was 9.3% in postmenopausal women, and 0.7% in men after 50 years of age. The percentage difference in prevalence range from 60.5–163.6%, when using reference values from T(DXA), T(NHANES), and T(CHN). Comparing diagnosis using T(DXA) and T(SG) cut-off values, 28 versus 15 women were diagnosed as osteoporotic respectively.  The kappa statistics was 0.81 for women and 0.85 for men. Conclusion: Our study shows that T-scores provided by DXA manufacturer over-diagnosed osteoporosis in Singaporeans, and the prevalence of osteoporotic conditions is not accurately represented. This over-diagnosis may result in unnecessary treatment in some individuals.