The relationship between fall risk, trochanteric soft tissue thickness, and hip fracture risk in older adults

Current fracture risk assessment does not directly include fall probability, despite most hip fractures resulting from falls. Additionally, the role of trochanteric soft tissue thickness (TST) in hip fracture risk remains unclear. This study aimed to develop a subject-specific fall risk tool and test whether incorporating fall probability and TST improves hip fracture prediction beyond FRAX alone in older adults from the AGES-Reykjavik study. Baseline data from 3242 individuals (58% women) were used to predict repeated falls (≥2 in 12 months) at follow-up (~5 years later) via multivariate logistic regression, considering age, sex, fall history, neuromuscular function, dynamic balance, and medication use. In a case-cohort study (698 hip fractures, 1348 controls; median follow-up 10 years), Cox proportional hazards models assessed hip fracture risk. We compared the predictive value of fall probability and TST combined with FRAX against FRAX alone using time-dependent AUC at 5-, 10-, and 16-year follow-up. At follow-up, 295 individuals had ≥2 falls in the past year. The best model for future falls included a timed up-and-go test, fall history, and grip strength. The probability of falling predicted incident hip fracture and improved hip fracture prediction beyond FRAX, in both men and women. The improved predictive value of fall risk was greater among men than women (e.g. AUC for predicting 10 yrs hip fracture risk, 0.83 (95%CI 0.79-0.87) in men vs 0.75 (95%CI 0.72-0.78) in women). Lower TST was linked to higher hip fracture risk in women but not men. However, adding TST to a model with fall probability and FRAX among women did not enhance time-dependent AUC (p>0.10). In conclusion, fall probability significantly improves hip fracture prediction beyond FRAX, particularly in men. Thus, subject-specific fall risk assessment may enhance clinical evaluation of hip fracture risk in older adults.