Prevalence of hip fracture risk factors in women aged 70 years and over. 
We estimated the prevalence of common risk factors for hip fracture and the numbers needed to treat (NNT) to prevent a hip fracture in various high-risk population groups, using a postal risk factor survey of women aged 70 years and above from General Practices in Grampian and Yorkshire.  Recorded risk factors included prior fracture of any type; low body weight; smoking; and family history of fracture.  The prevalence rates of hip fracture risk factors were 34%, 7% and 11% for previous fracture, maternal hip fracture and smoking, respectively for the Grampian practices (low body weight being defined as falling in the lowest quartile) and 34%, 7% and 7% for a single practice in the York area.  Applying previously published estimates of risk, NNT analysis produced a value of about 300 for women with no risk factors, whilst for women with three risk factors it was between 32 and 71, depending on which risk factors were present and assuming intervention reduced fracture rates by 30% or 50%.  Groups of women at high risk of hip fracture can easily be identified in primary care and offered treatment, with realistic prospects of hip fracture prevention.