Association of heel bone mineral density with incident dementia among ageing adults: a population-based study from the UK Biobank

BACKGROUND: Osteoporosis and dementia are two common disorders mainly affecting ageing population, and heel estimated bone mineral density (eBMD) measured by quantitative ultrasound (QUS) has been demonstrated to be a reliable and non-invasive method for assessing skeletal health. The aim of this study is to determine the association between eBMD and incident dementia in older adults. METHODS: This retrospective cohort study employs UK Biobank data of 131,030 adults aged ≥ 60 years without dementia at baseline. Cox proportional-hazards models were used to investigate the association between eBMD and incident dementia, with the C-index evaluating the discriminative potential of eBMD. RESULTS: Among participants (52.1% women, median [IQR] age was 64 [62-66] years), there were 4,572 cases (3.5%) of incident dementia. Minimal model showed that participants with low eBMD (< 0.467 g/cm²) had a 14% increase in the rate of dementia incidence (HR 1.14, 95% CI 1.06-1.23; P <.001), and each standard deviation (SD) decrease in eBMD was associated with a 49% increase in dementia risk (HR 1.49, 95% CI 1.19-1.86; P <.001). Such association remained significant after further adjustment for potential confounders. Stratified analyses revealed that lower eBMD increased dementia risk in male participants (HR 1.17, 95% CI 1.06-1.31; P =.003) and in participants with neutral (HR 1.18, 95% CI 1.05-1.33; P =.007) or low genetic risk (HR 1.36, 95% CI 1.01-1.83; P =.04). Sensitivity analyses showed similar results. However, discriminative analyses showed minimal improvement after adding eBMD to dementia prediction models. CONCLUSION: Lower heel eBMD is independently associated with increased dementia risk among older adults.