BMD enhances clinical risk factors in predicting ten-year risk of osteoporotic fractures in Chinese men: the Hong Kong Osteoporosis Study

Abstract

Introduction: Clinical risk factors with or without bone mineral density (BMD) measurements are increasingly recognized as reliable predictors of absolute fracture risk. Clinical risk factors may be population specific. The purpose of this prospective study was to determine the risk factors for osteoporotic fractures and to predict the 10-year risk of fractures in Southern Chinese male population. Materials and Methods: This is a part of the Hong Kong Osteoporosis Study. 1,525 community-dwelling, treatment-naive Southern Chinese men aged 50 or above were recruited. Baseline demographic characteristics and clinical risk factors were obtained, and BMD at the spine and hip were measured. Subjects were prospectively followed for incident low trauma fracture. Ten-year risk of major osteoporotic fracture and hip fracture was calculated using Cox proportional hazards models. Results: The mean age of subjects was 68 ± 10 years. After 3.5 ± 3 (1–14) years of follow-up, 36 non-traumatic incident fractures were reported. The incident rates for osteoporotic fractures and hip fracture were 676/100,000 and 132/100,000 person-years respectively. The most significant predictors of osteoporotic fracture were history of fall (odds ratio 14.5) and fragility fracture (odds ratio 4.4). Other predictive factors included outdoor activity <60 minutes/day, BMI < 20 kg/cm2, difficulty bending forward, use of walking aid, and age ≥ 65 years. Each SD reduction in BMD at spine or hip was associated with 1.7 to 2.6-fold increase in fracture risk. Subjects with 5 or more clinical risk factors had an absolute 10-year risk of osteoporotic fracture of 6.2%, which increased to 18.2% if they also had total hip BMD T-score ≤ -2.5. Addition of BMD information (total hip T-score score ≤ -2.5) significantly enhanced fracture risk prediction when compared to clinical risk factors only (omnibus test p=0.001). Men with multiple risk factors and low BMD T-scores have a higher absolute fracture risk while men with no risk factors and normal BMD have a lower fracture risk than that predicted by FRAX. Conclusions: Clinical risk factors are population specific and the addition of BMD measurement to risk factor assessment improves fracture risk prediction in Southern Chinese men.