Low Bone Mineral Density With Risk of Dementia: A Prospective Cohort Study

Objectives Osteoporosis and dementia often coexist, but the association between the 2 diseases remains unclear. This study aimed to investigate the relationship between bone mineral density (BMD) and the risk of incident dementia. Design Prospective cohort study, the Hong Kong Osteoporosis Study (HKOS). Setting and Participants Data were from the HKOS and the Clinical Data Analysis and Reporting System (CDARS) in Hong Kong. A total of 5803 participants aged ≥40 years and free of dementia were included in the HKOS. Methods The baseline BMD at the lumbar spine, femoral neck, trochanter, and total hip were measured using dual-energy x-ray absorptiometry (DXA). The incidence of dementia was identified using their International Classification of Diseases, Ninth Revision, codes. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% CIs. Results The median follow-up time of the HKOS was 16.8 years. Higher BMD T scores at the lumbar spine, trochanter, and total hip were significantly associated with the reduced risk of dementia with the respective HR of 0.85 (95% CI 0.76-0.95; P = .004), 0.78 (95% CI 0.68-0.90; P < .001), and 0.82 (95% CI 0.72-0.93; P = .003). The subgroup analyses showed that associations were significant in women but not in men, whereas the associations were unaltered after adjusting for serum estradiol. Conclusions and Implications Low BMD was associated with an increased risk of dementia, particularly in women. Future studies evaluating the clinical usefulness of BMD on dementia prediction and management are warranted.