Validation of FRAX and the impact of self-reported falls among elderly in a general population: the HUNT study, Norway

Abstract

Summary Fracture Risk Assessment Tool (FRAX) without bone mineral density (BMD) for hip fracture prediction was validated in a Norwegian population 50–90 years. Fracture risk increased with higher FRAX score, and the observed number of hip fractures agreed well with the predicted number, except for the youngest and oldest men.

Self-reported fall was an independent risk factor for fracture in women.

Introduction The primary aim was to validate FRAX without BMD for hip fracture prediction in a Norwegian population of men and women 50–90 years. Secondary, to study whether information of falls could improve prediction of fractures in the subgroup aged 70–90 years.

Methods Data were obtained from the third survey of the Nord-Trøndelag Health Study (HUNT3), the fracture registry in Nord-Trøndelag, and the Norwegian Prescription Database (NorPD), including 15,432 women and 13,585 men.

FRAX hip without BMD was calculated, and hip fractures were registered for a median follow-up of 5.2 years.

The number of estimated and observed fractures was assessed, ROC curves with area under the curve (AUC), and Cox regression analyses. For the group aged 70–90 years, self-reported falls the last year before HUNT3 were included in the Cox regression model.

Results The risk of fracture increased with higher FRAX score. When FRAX groups were categorized in a 10-year percentage risk for hip fracture as follows, <4, 4–7.9, 8–11.9, and ≥12%, the hazard ratio (HR) for hip fracture between the lowest and the highest group was 17.80 (95% CI: 12.86–24.65) among women and 23.40 (13.93–39.30) in men. Observed number of hip fractures agreed quite well with the predicted number, except for the youngest and oldest men. AUC was 0.81 (0.78–0.83) for women and 0.79 (0.76–0.83) for men. Self-reported fall was an independent risk factor for fracture in women (HR 1.64, 1.20–2.24), and among men, this was not significant (1.09, 0.65–1.83).

Conclusions FRAX without BMD predicted hip fracture reasonably well. In the age group 70–90 years, falls seemed to imply an additional risk among women.