Table 3 Calculation of downstream costs of benzodiazepine use in the elderly related to hip fractures

Estimated adjusted rate ratio of hip fractures in elderly people (≥50 years) taking benzodiazepines compared to those who were not = 1.52 (95% CI: 1.37-1.68) [23]

Proportion of elderly people (≥65 years) dispensed benzodiazepines (current study) = 0.067

Estimated number of osteoporotic & osteopenic hip fractures in 2016 = 26,232 [34]

Estimated average direct cost of a hip fracture in 2012 = $32,569 AUD [34]

Proportion of hip fractures attributable to benzodiazepines

\( =\frac{\left(1.52-1\right)\ast 0.067}{\left[\left(1.52-1\right)\ast 0.067\right)\Big]+1}\kern0.5em =0.033 \)

Number of hip fractures attributable to benzodiazepines = 0.033*26,232 = 883

Excess costs of hip fractures related to benzodiazepine use in the elderly

= 883*$32,569 = $29 million (95% CI: $20-$38 million) AUD