THE IMPORTANCE OF FALL HISTORY IN FRACTURE RISK ASSESSMENT

We are most grateful to Dr Kawada for their comments on our study. We were delighted that they felt the topic of importance and were so supportive of the methodology and results. They correctly point out that, in keeping with the FRAX model(1), we utilised height and weight as clinical risk factors in the assessment of fracture prediction(2). In our model, the hazard ratios (HR) for fracture associated with a history of falls were 6.96 and 2.64 in men and women respectively after adjustment for clinical risk factors and femoral neck bone mineral density (BMD)(3). When body mass index (BMI) was utilised in place of height and weight, the values changed little (6.68 and 2.75 respectively).

We entirely agree that the limited number of fractures in men will affect the stability of the male model risk prediction. In this regard, we would point out the imprecision of our estimates of risk, as illustrated by the 95% confidence intervals for men. Of course, our research paves the way for similar studies using larger populations or longer follow up to increase fracture numbers and statistical power.

The correspondent also correctly identifies the important issue of exercise as a predictor of fracture. This was not incorporated in our study models as it is not a constituent of the FRAX algorithm. However assessments have been made in our cohort of self-perceived walking speed and habitual physical activity. The latter was calculated as a standardised score ranging from 0–100 derived from frequency of gardening, housework, climbing stairs and carrying loads in a typical week. Higher scores indicated greater levels of activity(4). An association was demonstrated between faster walking speed and a lower rate of both falls and fractures in women. However, when included in our fracture prediction models, these variables did not materially affect the HR for fracture in either sex, and multivariate analysis did not reveal any association between habitual physical activity and subsequent fracture in either men or women.

Overall our study confirms the role of clinical risk factors and BMD in fracture risk prediction and provides evidence that fall history may further augment this. These findings are in accord with the recommendations of the FRAX Clinical Task Force(5) that suggested falls be accounted for alongside FRAX. They are also commensurate with their suggestion that a 30% increased risk of fracture be applied for every additional fall in the preceding year.