Original researchThe impact of adherence on sports injury prevention effect estimates in randomised controlled trials: Looking beyond the CONSORT statement
Introduction
There has been increasing recognition of the need to formally evaluate the preventive capabilities of a range of sports injury preventive interventions. The sequence of prevention1 has been widely used in sports injury prevention research. More recently, the model has been extended to emphasise the need for both efficacy and effectiveness studies as well as an increased focus on actual behaviours within the context of implementing preventive interventions.2 From a theoretical and quality evidence perspective, the best way to evaluate the effect of any preventive intervention is by performing a randomised controlled trial (RCT).3
Although the RCT is considered the gold standard in research,4 there are some important considerations and limitations when the methodology is applied to sports injury prevention interventions.5 Amongst others, most sports injury prevention RCTs require athletes to adopt some form of behaviour change for injury reduction benefits.6 The long follow-up time that is required to demonstrate such behaviour change can result in significant loss to follow-up.7, 8, 9 Another important consideration that determines the outcome of an RCT is adherence to the intervention or the required behaviour change. Adherence in sports injury prevention research is a term used to indicate the athlete's correct following of the prescribed intervention. Large cohorts are harder to control and it can be difficult to directly influence the behaviours of individuals. This can lead to compromised adherence, as there is increased dependence on the athletes’ own motivation levels.
Sports medicine research can be used to exemplify the importance of intervention adherence on RCT outcome. For example, multiple studies have studied the effectiveness of exercise training programmes for the prevention of injuries. Many such studies showed that these training programmes can prevent injuries.10, 11, 12, 13, 14, 15 In contrast, two recent studies have failed to show a preventive effect, but did report suffering from poor adherence with the prescribed intervention.16, 17 The impact on outcome of ‘non-adherence’ with specific interventions on injury reductions has also been highlighted in other randomised controlled trials of lower limb injury prevention interventions in soccer18, 19, 20 and for protective equipment in Australian Football.21
With respect to analysis of RCT study results, the CONSORT statement advocates intention-to-treat (ITT).22 By using an ITT approach, RCTs aim to minimise selection bias and the likelihood that confounding factors influence results. However, poor adherence to the intervention tends to dilute treatment effects when analyses go by the ITT approach.23 A different approach that has a stronger focus on the efficacy of an intervention is analysis by treatment actually received, i.e. per-protocol analysis (PP).24 By solely analysing adherers to the intervention the maximal achievable effect of the intervention is shown. Recently, studies on protective equipment in football17, 25 and studies on injury prevention in soccer17, 18 have adopted the PP approach.
What is lacking from the literature is a formal assessment of the differences in injury prevention outcome effect sizes derived from a PP approach compared to an ITT analysis, although one rugby helmet study did present the results of both an ITT and PP analysis.25 Therefore, the overall aim of the present study was to investigate the estimated outcome effects of a preventive sports injury intervention when analysed by means of a PP analysis and to compare this with prior outcome effects estimated from an ITT approach. For this purpose, we have used data from a published RCT with 522 participants on the prevention of ankle sprain recurrences through an 8-week home based unsupervised neuromuscular training programme.26 The main study design, intervention and outcomes are described in detail elsewhere.26, 27 Briefly, a RCT was conducted in athletes (n = 522) who sprained their ankle. Athletes all received treatment according to usual care, after which they were randomised to a control group or an intervention group. Athletes allocated to the intervention group received an additional 8-week proprioceptive training programme after treatment by usual care. This programme consisted of 3 proprioceptive training sessions per week, with a maximum duration of 30 min per session. The full programme is described elsewhere.27 Cox regression analysis according to the ITT principle showed in this study that the risk for incident ankle sprain recurrences was significantly lower in the intervention group as compared to the control group (HR = 0.63; 95% CI: 0.45–0.88).26
Section snippets
Methods
This paper reports a new PP analysis on these data, taking adherence rates into account. As this adherence data has not been previously reported, the methods used to collect it are reported here.
During a one year follow-up, athletes reported all sudden inversions of the same ankle and details of their sports participation for each training session through monthly questionnaires. The first and second monthly questionnaires of the intervention participants also contained a Likert item on
Results
Fifty-eight (23%) intervention group athletes indicated to have fully adhered to the eight-week proprioceptive training programme; 75 (29%) intervention group athletes indicated to have been partially adhered; 89 (35%) responded in such a way that they were classified as not adherent (Table 1). Adherence to the training programme was unknown for 33 (13%) athletes, since they did not complete the questionnaires. Five out of 266 control group athletes (2%) reported to have performed some sort of
Discussion
When compared to the ITT analysis outcomes of the RCT reported by Hupperets et al.,26 these secondary analyses based on a PP approach analyses showed that the established intervention effect was over threefold higher compared to when an ITT approach was utilised. The ITT approach resulted in a Hazard Ratio of 0.63 (95% CI: 0.45–0.88) in favour of the intervention group, whereas the PP approach resulted in a Hazard Ratio of 0.18 (95% CI: 0.07–0.43). This means that the larger part of the ITT
Conclusion
Although the CONSORT statement is widely used to guide the reporting of RCTs in many major journals, in the specific example of sports injury prevention research additional analysis strategies might also apply in addition to the favoured ITT. From the present study it can be concluded that under the influence of nonadherence to the allocated intervention, differences in effect sizes can be found depending on the type of analysis that is chosen. In determining effect size of an intervention
Practical implications
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Outcomes of intervention studies are heavily biased by adherence to the allocated intervention.
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In randomised controlled trials a per-protocol analysis conducted alongside an intention-to-treat analyses provides insight into the efficacy and true potential of the intervention.
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Assessment of adherence to an intervention programme and the subsequent reporting of adherence is of critical importance for RCTs.
Acknowledgements
This study is supported by a grant from the Netherlands Organization for Health Research and Development (ZonMw), grant number 750-20-002. Caroline Finch was supported by a National Health and Medical Research Council (of Australia) Principal Research Fellowship (NHMRC ID: 565900). No author or related institution has received any financial benefit from research in this study.
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2017, Journal of Science and Medicine in SportCitation Excerpt :Although the effectiveness of such preventive programs has been shown in controlled studies, the majority of individuals involved were neither able nor willing to comply with the prescribed program. Performing only part of such preventive exercise programs has been shown to be ineffective in reducing the risk of an (recurrent) ankle sprain.5,6 In recognition of the major problem that ankle sprains continue to pose for those involved in physical activities and sports, it is, therefore, of importance that available programs are enhanced in such a way that compliance with the exercise scheme is increased.
Interventions preventing ankle sprains; previous injury and high-risk sport participation as predictors of compliance
2016, Journal of Science and Medicine in SportCitation Excerpt :When translating evidence-based preventive interventions into daily practice in sports, an important issue to address is compliance.1 In sports injury prevention research, compliance is a term used to indicate the athlete's correct execution of the prescribed intervention.2 In the preferred research design setting for the evaluation of the efficacy of sports injury preventive interventions, i.e., a randomized controlled trial (RCT), compliance can be optimized by the use of a well-defined protocol that must be complied with.