Association of Bone Mineral Density and Dementia: The Rotterdam Study

Background & Objective: Low bone mineral density and dementia commonly co-occur in the elderly, with bone loss accelerating in dementia patients due to physical inactivity and poor nutrition. However, uncertainty persists over the extent to which bone loss already exists prior to the onset of dementia. Therefore, we investigated how dementia risk was affected by bone mineral density at various skeletal regions in community-dwelling older adults.

Methods: In a prospective population-based cohort study, bone mineral density at the femoral neck, lumbar spine, and total body and the trabecular bone score were obtained using dual-energy X-ray absorptiometry (DXA) in 3,651 participants free from dementia between 2002-2005. Persons at risk of dementia were followed up until 1 January 2020. For analyses of the association between bone mineral density at baseline and the risk of incident dementia, we used Cox proportional-hazards regression analyses, adjusting for age, sex, educational attainment, physical activity, smoking status, body mass index, systolic blood pressure, diastolic blood pressure, cholesterol level, high-density lipoprotein cholesterol, history of comorbidities (stroke and diabetes mellitus), and APOE genotype.

Results: Among the 3,651 participants (median age 72.3±10.0 years, 57.9% women), 688 (18.8%) developed incident dementia during a median of 11.1 years, of whom 528 (76.7%) developed Alzheimer’s disease. During the whole follow-up, participants with lower bone mineral density at the femoral neck (per SD decrease) were more likely to develop all-cause dementia (Hazard ratio [HR] total follow-up: 1.12, 95% Confidential interval [CI]: 1.02-1.23) and Alzheimer’s disease (HR total follow-up: 1.14, 95% CI: 1.02-1.28). Within the first ten years following baseline, the risk of dementia was greatest for groups with the lowest tertile of bone mineral density (femoral neck bone mineral density, HR0-10years 2.03; 95% CI, 1.39–2.96; total body bone mineral density, HR0-10years 1.42; 95% CI, 1.01–2.02; trabecular bone score, HR0-10years 1.59; 95% CI, 1.11–2.28).

Conclusions: In conclusion, participants with low femoral neck and total body bone mineral density and low trabecular bone score were more likely to develop dementia. Further studies should focus on the predictive ability of bone mineral density for dementia