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How big does the effect of an intervention have to be? Application of two novel methods to determine the smallest worthwhile effect of a fall prevention programme: a study protocol
  1. Marcia Rodrigues Franco1,
  2. Manuela L Ferreira1,
  3. Kirsten Howard2,
  4. Catherine Sherrington1,
  5. John Rose3,
  6. Terry P Haines4,
  7. Paulo Ferreira5
  1. 1Musculoskeletal Division, The George Institute for Global Health, Sydney, Australia
  2. 2School of Public Health, University of Sydney, Sydney, Australia
  3. 3Business School, Institute of Transport and Logistics Studies, University of Sydney, Sydney, Australia
  4. 4Faculty of Medicine, Nursing & Health Science, Monash University, Melbourne, Australia
  5. 5Faculty of Health Science, University of Sydney, Sydney, Australia
  1. Correspondence to Marcia Rodrigues Franco; mrcfranco{at}


Introduction This project concerns the identification of the smallest worthwhile effect (SWE) of exercise-based programmes to prevent falls in older people. The SWE is the smallest effect that justifies the costs, risks and inconveniences of an intervention and is used to inform the design and interpretation of systematic reviews and randomised clinical trials.

Methods and analysis This study will comprise two different methodological approaches: the benefit-harm trade-off method and the discrete choice experiment to estimate the SWE of exercise interventions to prevent falls in older people. In the benefit-harm trade-off method, hypothetical scenarios with the benefits, costs, risks and inconveniences associated with the intervention will be presented to each participant. Then, assuming a treatment effect of certain magnitude, the participant will be asked if he or she would choose to have the intervention. The size of the hypothetical benefit will be varied up and down until it is possible to identify the SWE for which the participant would choose to have the intervention. In the discrete choice experiment, the same attributes (benefits, costs, risks and inconveniences) with varying levels will be presented as choice sets, and participants will be asked to choose between these choice sets. With this approach, we will determine the probability that a person will consider the effects of an intervention to be worthwhile, given the particular costs, risks and inconveniences. For each of the two approaches, participants will be interviewed in person and on different occasions. A subsample of the total cohort will participate in both interviews.

Ethics and dissemination This project has received Ethics Approval from the University of Sydney Human Ethics Committee (Protocol number: 14404). Findings will be disseminated through conference presentations, seminars and peer-reviewed scientific journals.

  • Rehabilitation Medicine
  • Geriatric Medicine
  • Preventive Medicine

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