Clinical utility of one-third radius BMD in a population-based prospective cohort of older adults: Insights from the São Paulo Aging & Health (SPAH) study.

In older adults, incorporating one-third-radius BMD increased osteoporosis diagnoses and improved fracture risk prediction. Radius osteoporosis independently predicted fractures, outperforming spine BMD. Total hip BMD remained the strongest predictor. Adding radius measurements enhances detection of skeletal fragility, especially when hip data are unavailable or uncertain. PURPOSE: In older adults, one-third radius BMD may add value to fracture risk assessment because it is unaffected by degenerative changes that can inflate spine and hip BMD, although its prognostic utility remains uncertain. We aimed to determine whether one-third radius BMD predicts incident fractures independently or alongside spine and hip BMD, and to evaluate its contribution to osteoporosis classification relative to standard sites.

methodsThis cohort included 707 adults aged ≥65 years (63.5% women) from the São Paulo Ageing & Health (SPAH) study with baseline DXA scans at the spine, hip, and one-third radius. Fragility fractures were recorded over 4.3±0.8 years. Multivariate logistic regression models assessed associations between site-specific osteoporosis (T-score≤-2.5) or BMD (per SD decrease) and fracture risk.

resultsIncluding one-third radius BMD increased osteoporosis diagnoses by up to 8.6% in women and 8.2% in men, and by 11.1% and 15.7% among individuals who fractured. In women, osteoporosis at the one-third radius independently predicted fracture risk (RR=1.61; 95% CI: 1.04-2.48), whereas spine or hip osteoporosis alone did not. In continuous models, lower hip and radius BMD-but not spine BMD-were associated with higher risk; total hip BMD showed the strongest association and remained significant in multisite models (RR=1.72; 95%CI: 1.06-2.78; p=0.028), while radius BMD lost significance. In men, few fracture events precluded multivariable analysis.

conclusionsIncluding one-third radius BMD improves fracture risk prediction in older adults, particularly when hip measurements are unavailable or inconclusive. It captures skeletal fragility that spine BMD may miss, enhancing identification of high-risk individuals for treatment.