Influence of fall related factors and bone strength on fracture risk in the frail elderly.

INTRODUCTION: When subjects are selected on the basis of fall risk alone, therapies for osteoporosis have not been effective. In a prospective study of elderly subjects at high risk of falls, we investigated the influence of bone strength and fall risk on fracture.
METHODS: At baseline we assessed calcaneal bone ultrasound attenuation (BUA) as well as quantitative measures of fall risk in 2005 subjects in residential care. Incident falls and fractures were recorded (median follow-up 705 days).
RESULTS: A total of 6646 fall events and 375 low trauma fracture events occurred. The fall rate was 214 per 100 person years and the fracture rate 12.1 per 100 person years. 82% of the fractures could be attributed to falls. Although fracture rates increased with decreasing BUA (incidence rate ratio 1.94 for lowest vs. highest BUA tertile, p<0.002), incident falls also affected fracture incidence. Subjects who fell frequently (>3.15 falls/per person year) were 3.35 times more likely to suffer a fracture than those who did not fall. Some fall risk factors such as balance were associated with the lowest fracture risk lowest in the worst performing group. Multivariate analysis revealed higher fall rate, history of previous fracture, lower BUA, lower body weight, cognitive impairment and better balance as significant independent risk factors for fracture.
CONCLUSIONS: In the frail elderly, both skeletal fragility and fall risk including the frequency of exposure to falls are important determinants of fracture risk.