Adjusting conventional FRAX estimates of fracture probability according to the number of prior falls in the preceding year

A greater propensity to falling is associated with higher fracture risk. This study provides adjustments to FRAX-based fracture probabilities accounting for the number of prior falls.

Introduction: Prior falls increase subsequent fracture risk but are not currently directly included in the FRAX tool. The aim of this study was to quantify the effect of the number of prior falls on the 10-year probability of fracture determined with FRAX®.

Methods: We studied 21,116 women and men age 40 years or older (mean age 65.7 ± 10.1 years) with fracture probability assessment (FRAX®), self-reported falls for the previous year, and subsequent fracture outcomes in a registry-based cohort. The risks of death, hip fracture, and non-hip major osteoporotic fracture (MOF-NH) were determined by Cox proportional hazards regression for fall number category versus the whole population (i.e., an average number of falls). Ten-year probabilities of hip fracture and major osteoporotic fracture (MOF) were determined according to the number of falls from the hazards of death and fracture incorporated into the FRAX model for the UK. The probability ratios (number of falls vs. average number of falls) provided adjustments to conventional FRAX estimates of fracture probability according to the number of falls.

Results: Compared with the average number of falls, the hazard ratios for hip fracture, MOF-NH and death were lower than unity in the absence of a fall history. Hazard ratios increased progressively with an increasing number of reported falls. The probability ratio rose progressively as the number of reported falls increased. Probability ratios decreased with age, an effect that was more marked the greater the number of prior falls.

Conclusion: The probability ratios provide adjustments to conventional FRAX estimates of fracture probability according to the number of prior falls.