The distribution of FRAX(®)-based probabilities in women from Japan.

New assessment guidelines for osteoporosis in Japan include the use of the WHO risk assessment tool (FRAX) that computes the 10-year probability of fracture. The aim of this study was to determine the distribution of fracture probabilities and to assess the impact of probability-based intervention thresholds in women from Japan aged 50 years and older. Age-specific simulation cohorts were constructed from the prevalences of clinical risk factors and femoral neck bone mineral density to determine the distribution of fracture probabilities as assessed by FRAX. These data were used to estimate the number and proportion of women at or above a 10-year fracture probability of 5, 10, 15, 20, 25, and 30 %. In addition, case scenarios that applied a FRAX probability threshold of 15 % were compared with current guidance. In the absence of additional criteria for treatment, a 15 % fracture probability threshold would identify approximately 32 % of women over the age of 50 years (9.3 million women) as eligible for treatment. Because of expected changes in population demography, the 15 % fracture probability threshold would capture approximately 38 % of women over the age of 50 years (12.7 million women), mainly those aged 80 years or older. The introduction of a FRAX threshold of 15 % would permit treatment in women with clinical risk factors that would otherwise fall below previously established intervention thresholds. The incorporation of FRAX into assessment guidelines is likely to redirect treatments for osteoporosis from younger women at low risk to elderly women at high fracture risk.