Definitions and methods of measuring and reporting on injurious falls in randomised controlled fall prevention trials: a systematic review

Table 5 Hypothetical examples of sample size requirements for RCTs of injurious falls prevention by risk group

Outcome	Incidence in study population	Required sample size
Low risk (25% lower than intermediate risk)
Fallers¹	37.50%	2246
≥ 1 injurious falls	15.00%	7408
≥ 1 fractures	3.75%	33222
≥ 1 hip fractures	2.25%	56168
Intermediate risk
Fallers¹	50.00%	1386
≥ 1 injurious falls	20.00%	5258
≥ 1 fractures	5.00%	24618
≥ 1 hip fractures	3.00%	41828
High risk (25% higher than intermediate risk)
Fallers¹	62.50%	868
≥ 1 injurious falls	25.00%	3966
≥ 1 fractures	6.25%	19456
≥ 1 hip fractures	3.75%	33222

Assumptions for sample size calculation: effect size -15% with respect to all outcomes, statistical power 80%, significance-level 5%, two-sided tests, not adjusted for multiple testing.
¹Fallers reflect those study participants who experience any fall (injurious or not injurious) during the study period

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