Interpreting the null result

doi:10.1136/bmj.39549.430162.3A

BMJ 2008;336:847 (19 April), doi:10.1136/bmj.39549.430162.3A

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Preventing falls among older people in hospital

Interpreting the null result

The first 150 words of the full text of this article appear below.

Evidence that multifaceted interventions in acute hospitalsare ineffective is limited,¹ with most studies based on rehabilitationunits² and only one other large cluster randomised controlledtrial in an acute setting.³ This showed a significant reductionin falls after the introduction of multifaceted interventions,as did other large acute hospital studies of before and afterdesign.⁴ So what explains the disparity in the results? It ishard to fault the quality of design in this study, so unpackingthe "black box" of the intervention is crucial in understandingthe null result.

Firstly, as the authors point out, control wards in their studymay have introduced some or all of the interventions too—hopefullycontrol ward patients were also provided with "appropriate walkingaids." Osmosis is particularly likely, given the study durationof three years and interventions based on guidance issued in1998.⁵ It is harder to effect a difference if good . . . [Full text of this article]

Frances Healey, patient safety manager

¹ School of Health and Social Care, University of Reading, Reading RG1 5AQ, ² National Patient Safety Agency, Leeds LS2 7UE

d.oliver@reading.ac.uk

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