Bone mass, size and previous fractures as predictors of prospective fractures in an osteoporotic referral population.

The influence of bone mass, bone size and previous low energy fractures upon prospective fractures has not been investigated in a referral osteoporotic population. We investigated the association between bone mass, bone size, previous fractures, body constitution, and prospective validated fractures in 5701 women and 1376 men, aged 30 years and older. Bone mass measurements of the femoral neck were collected at a single study center in Sweden. Most of the subjects were measured on suspicion of osteoporosis. Data on validated low energy retrospective and prospective fractures in the cohort were collected from the corresponding health care district. Bone mineral density (BMD, g/cm(2)) and estimated volumetric BMD (vBMD, g/cm(3)) were shown to be good independent predictors for fracture in both women and men (Hazard ratio per standard deviation decrease (HR)=1.27-1.52, p<0.05). Bone size did not predict prospective fractures in either sex (HR=0.91-0.99, p>0.05), and bone size completely explained the higher BMD in men than in women. In women, retrospective low energy fractures (HR=1.78, p<0.001) and height (HR=1.02, p=0.006) were additional independent predictors of osteoporotic fractures after adjusting for age and BMD. In conclusion, we show that in a large osteoporotic referral population, age, BMD and previous fractures are independent predictors of prospective low energy fractures. These results add additional strength to the recent change in focus towards a multivariate analysis when assessing the future risk of fracture.