Variation in fracture rates by country may not be explained by differences in bone mass

It is unclear whether the high fracture incidence in Sweden compared with other countries is related to low bone mass. We present and compare bone mineral density (BMD, g/cm(2)) at the femoral neck in a mainly osteoporotic referral population consisting of 2,031 men and 6,932 women with that of previous population-based cohorts. BMD measurements were collected at a single study center in Sweden, and data on validated hip fractures were collected from the corresponding health-care district and the cohort investigated. The BMD values of our cohort were similar to those of population-based cohorts from other countries. In contrast, the total incidence of hip fractures in 80-year-old women and men in the health-care district where our BMD measurements were performed was high (1.8% and 0.9%, respectively). The correlation between age and BMD was more negative in men aged 20-49 years than in women of the same age group (-0.011 vs. -0.006 g/cm(2) yearly, P < 0.001). In contrast, at 50-80 years of age, more negative regression coefficients were seen in women (-0.007 vs. -0.004 g/cm(2) yearly, P < 0.001 for comparison). In conclusion, a low BMD may not be the key factor explaining Sweden's comparatively high fracture incidence. In our cross-sectional data, age trends in BMD at the femoral neck differ between men and women. It would be highly interesting to further study the underlying causes of the global variations in fracture incidence rates.