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

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

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
  1. 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.
  2. 1Fallers reflect those study participants who experience any fall (injurious or not injurious) during the study period