A population-based study on the association between dementia and hip fractures in 85-year olds.

The association between dementia and hip fracture was studied in a representative sample of 85-year olds (N = 485). The diagnosis of dementia was made according to the DSM-III-R. The prevalence of hip fracture was obtained by history and inspection of the hip. Bone mineral density was measured with dual photon absorptiometry of the right calcaneus. Hip fracture was associated with both Alzheimer's disease (p < 0.01) and vascular dementia (p < 0.01) in women, but not in men. Among women with dementia, the rate of hip fracture was more than twice that found in the general population (32.7% vs 13.6%). Bone density was not associated with dementia or hip fracture. Body mass index and body weight were lower in women with dementia and in women with hip fracture. The prevalence of hip fracture was also increased in subjects who used psychotropic drugs, especially tricyclic antidepressants. A logistic multiple regression analysis showed that dementia, use of antidepressants and gender independently contributed to hip fracture. The reason why subjects with dementia are at increased risk for hip fractures may be that these subjects have a defective neuromuscular regulation, gait apraxia, use more antidepressants, and have a lower body mass index. Another explanation of the association may be that surgery and anesthesia give rise to systemic hypotension that leads to cerebral hypoperfusion and ischemic and neuronal death in vulnerable brain areas, and as a consequence may lead to dementia or worsen the symptoms in subjects already affected by dementia.