Hip fractures occurring in older adults are a common and serious condition, frequently leading to functional decline, morbidity, and mortality. As one consequence of the aging of America, the incidence of hip fractures is increasing.¹ Fracture risk doubles every decade after age 50 years.² In the United States, 350 000 hip fractures occur yearly,³ and this number may grow to 500 000 by 2040.⁴ Half of those with hip fractures fail to regain their prefracture mobility, and 20% or more die within a year of surgery⁵; a fourth of those who previously lived independently require long-term nursing home care.⁶

Dementia and hip fractures are 2 conditions that are seen primarily in older adults, and both are associated with substantial morbidity and mortality. An individual with dementia is up to 3 times more likely than a cognitively intact older adult to sustain a hip fracture. This may occur via several mechanisms, including (1) risk factors that are common to both outcomes; (2) the presence of dementia increasing hip fracture incidence via intermediate risk factors, such as falls, osteoporosis, and vitamin D; and (3) treatment of dementia causing side effects that increase hip fracture risk. We describe a model that applies these 3 mechanisms to explain the relationship between dementia and hip fractures. Comprehensive understanding of these pathways and their relative influence on the outcome of hip fracture will guide the development of effective interventions and potentially improve prevention efforts.