1

An Evaluation of the

Effectiveness of the Lidcombe

Program of Early Stuttering

Intervention

Mark A. Jones

A thesis submitted in fulfilment of the requirements

for the degree of Doctor of Philosophy

Australian Stuttering Research Centre

The University of Sydney

June 2005

2

Abstract

3

This thesis presents a randomised controlled trial of the Lidcombe Program of

Early Stuttering Intervention. The Lidcombe Program was developed for the

treatment of stuttering in preschool-age children. The effectiveness of the Lidcombe

Program was compared to a control group in a parallel group randomised controlled

trial with blinded outcome assessment. A number of supplementary studies were

conducted in support of the trial; two literature reviews, two retrospective file audits

and a statistical simulation study.

A review of randomised studies of treatments for stuttering showed that there

have been 27 such studies published in English language journals. Of these only one

was devoted to a treatment for early stuttering and that was the Lidcombe Program.

The randomised study showed that 3 months of this treatment was associated with a

lower level of stuttering compared to a control group who received no treatment.

However, with a sample size of 23, this study lacked power and the children did not

receive a full course of treatment. Despite these limitations, this study provided

evidence that a medium to large effect size could be anticipated in an adequately

powered and properly conducted randomised controlled trial.

Two retrospective file audit studies of children treated with the Lidcombe

Program were conducted in Australia and Britain. One purpose of these file audits

was to obtain information relevant to the design and conduct of the randomised

controlled trial. Data from the case reports on more than 300 children from the two

sites were included in a meta-analysis. Results showed that a median of 11 weekly

clinic sessions were required for children to attain the criteria for low levels of

stuttering for completion of Stage 1 of the Lidcombe Program. Approximately 90%

of children had achieved those criteria within 6 months of beginning treatment and

almost all children had achieved them within 1 year.

4

There were two treatment sites for the randomised controlled trial: the

University of Canterbury (Christchurch, New Zealand) and the Stuttering Treatment

and Research Trust (Auckland, New Zealand). A total of 54 preschool-age children

were recruited: 29 to the Lidcombe Program and 25 to the control group. Analysis

with t-test showed a highly statistically significant difference (p = 0.003) at 9-months

post-randomisation. The mean percentage of syllables stuttered (%SS) at 9-months

post-randomisation was 1.5 (SD = 1.4) for the Lidcombe Program group compared to

3.9 (SD = 3.5) for the control group, resulting in a treatment effect of 2.3 %SS (95%

confidence interval: 0.8-3.9). This treatment effect was more than double the

minimum clinically worthwhile difference specified in the trial protocol. These

results show that the Lidcombe Program is significantly more effective than natural

recovery for reducing stuttering levels in preschool children. The Lidcombe Program

is the first early stuttering treatment to be shown to be more effective than natural

recovery in a randomised controlled trial.

5

Acknowledgments

6

This thesis represents the work of many and I would like to thank all those

who contributed to the research it describes. In particular I acknowledge my

supervisors Mark Onslow and Ann Packman who provided the wonderful

opportunity for me to undertake this research as well as guidance and support to

ensure it was completed satisfactorily. I also thank Val Gebski who provided much

needed methodological advice and constructive criticism when it was warranted.

With regard to the randomised trial I acknowledge Tika Ormond, Marjorie

Blakely and Shelley Williams, who were the speech pathologists who treated the

children in Christchurch and Auckland. Tika and Shelley also had the unenviable

task of rating hundreds of tapes of children’s speech. I also thank Ilsa Schwarz from

the University of Canterbury (she is now located at the University of Tennessee) for

her support as well as Peta Forder from the National Health & Medical Research

Council Clinical Trials Centre who performed the randomisations for the trial. The

trial would not have been possible without the generosity of the children and parents

who participated. In particular I acknowledge all those families that remained in the

trial until the final follow up was completed especially those in the control group.

With regard to the papers that have been published I thank all the co-authors

outlined in the next section as well as the many helpful editorial consultants who

reviewed the manuscripts. I thank my supervisors at Queensland Health and the

University of Queensland who allowed me to finish this thesis as part of my work

duties and Elisabeth Harrison who loaned me her doctoral thesis. Finally I thank my

family for their support, in particular my wife Mitsuyo Taya and father Colin Jones.

7

Preface

8

The section in Chapter 2 describing randomised controlled trials was largely

taken from the publication by Jones, Gebski, Onslow, and Packman (2001). The

majority of the material included in Chapter 3 was published as Jones, Onslow,

Packman, and Gebski (2002). Mark Onslow proposed the survey of studies published

in the Journal of Speech, Language and Hearing Research and the Journal of Fluency

Disorders, and the author conducted the survey and wrote the manuscript. The other

three authors assisted with writing the manuscript.

The two retrospective studies described in Chapters 4 and 5 were published

as Jones, Onslow, Harrison, and Packman (2000) and Kingston, Onslow, Huber,

Jones, and Packman (2003). For the first study, Elisabeth Harrison was responsible

for the data collection and treatment of some of the children. The author provided

statistical analysis and contributed significantly to the scientific content of the

manuscript. All four authors contributed to writing the manuscript under the

direction of Mark Onslow. Mary Kingston was responsible for treatment of the

children and data collection in the second study. The author contributed statistical

analysis including the meta-analysis of the two studies. The five authors wrote the

manuscript with Anna Huber being in charge of collating the ideas from the other

authors and writing the original draft.

A very preliminary version of the study outlined in Chapter 6 was presented

as Jones (2002). The study as outlined in Chapter 6 has been submitted for

publication as Jones, Onslow, Packman, and Gebski (2005). The author designed and

conducted the study with methodological guidance from Val Gebski and clinical

input from Mark Onslow and Ann Packman. The manuscript was written by the

author with assistance from the other three authors.

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The randomised controlled trial of the Lidcombe Program included in

Chapter 7 was approved by the University of Sydney Ethics Committee and the

University of Canterbury Ethics Committee. The design of the trial has been

presented or published on three previous occasions: Jones, Gebski, Onslow, and

Packman (2000); Jones, Gebski, Onslow, and Packman (2001); and Jones, Blakely,

and Ormond (2003). Results from the trial have also been written up in a manuscript

and recently published as Jones, Onslow, Packman, Williams, Ormond, Schwarz,

and Gebski (2005). The author was responsible for the design and analysis of the trial

with methodological input from Val Gebski and clinical input from Mark Onslow

and Ann Packman. Tika Ormond and Shelley Williams treated the children as well as

collected and rated the tapes of the children’s speech. Writing of the manuscripts,

book chapter and presentation was conducted by the author with assistance from the

co-authors as listed above.

No part of this thesis has been submitted for any other degree at any other

institution.

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References

Jones, M., Onslow, M., Harrison, E., & Packman, A. (2000). Treating

stuttering in young children: Predicting treatment time in the Lidcombe Program.

Journal of Speech, Language and Hearing Research, 43, 1440-1450.

Jones, M., Gebski, V., Onslow, M., & Packman, A. (2000). Rationale,

Methods, and Design of a Randomised Controlled Trial of the Lidcombe Program of

Early Stuttering Intervention. Poster presentation at the Society for Clinical Trials

meeting in Toronto, Canada.

Jones, M., Gebski, V., Onslow, M., & Packman, A. (2001). Design of

Randomized Controlled Trials: Principles and Methods applied to a treatment for

early stuttering. Journal of Fluency Disorders, 26, 247-267.

Jones, M., Onslow, M., Packman, A., & Gebski, V. (2002). Statistical power

in stuttering research: A tutorial. Journal of Speech, Language and Hearing

Research, 45, 243-255.

Jones, M. (2002). Analysis of a trial of treatment for early stuttering. Poster

presentation at the International Clinical Trials Symposium in Sydney, Australia.

Kingston, M., Onslow, M., Huber, A. Jones, M., & Packman, A. (2003).

Predicting treatment time with the Lidcombe Program: Replication and meta-

analysis. International Journal of Language & Communication Disorders, 38, 165-

77.

Jones, M., Blakely, M., & Ormond, T. (2003). Chapter 14: The Lidcombe

Program in New Zealand. The Lidcombe Program of early stuttering intervention: A

clinicians guide. Austin, Texas: Pro-Ed.

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Jones, M., Onslow, M., Packman, A., Williams, S., Ormond, T., Schwarz, I.,

& Gebski, V. (2005). A randomised controlled trial of the Lidcombe Program for

early stuttering. British Medical Journal, 331, 659-661.

Jones, M., Onslow, M., Packman, A. & Gebski, V. (2005). Guidelines for

statistical analysis of percentage of syllables stuttered data. Submitted to the Journal

of Speech, Hearing and Language Research.

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Acronyms

13

The following acronyms are used throughout the thesis.

ASRC Australian Stuttering Research Centre, The University of Sydney

%SS Percentage of syllables stuttered

NHMRC National Health and Medical Research Council (of Australia)

START Stuttering Treatment and Research Trust

DMC Data Monitoring Committee

TMC Trial Management Committee

RCT Randomised controlled trial

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Table of contents

15

Abstract ........................................................................................................ 2

Acknowledgments ....................................................................................... 5

Preface.......................................................................................................... 7

Acronyms ................................................................................................... 12

Table of contents ....................................................................................... 14

List of Tables.............................................................................................. 17

List of Figures ............................................................................................ 20

PART ONE: INTRODUCTION..................................................................... 23

Chapter 1: The Nature and Treatment of Stuttering................................ 24

Introduction..........................................................................................................25 Early stuttering ....................................................................................................26 Natural Recovery from Early Stuttering ...........................................................29 Measurement of Stuttering..................................................................................30 Treatment Programs for Early Stuttering.........................................................33 The Present Thesis ...............................................................................................47

Chapter 2: Review of randomised studies of treatment for stuttering.. 49

Introduction..........................................................................................................50 Methods.................................................................................................................57 Results ...................................................................................................................59 Discussion..............................................................................................................82

Chapter 3: Statistical Power in Stuttering Research .............................. 88

Introduction..........................................................................................................89 Power and errors in statistical inference ...........................................................91 Fundamental Parameters that Influence Power ...............................................92 Other Parameters that Influence Power ............................................................97 Issues Associated with Failure to Consider Power a Priori .............................98 Example Sample Size Calculations...................................................................109 Discussion............................................................................................................114

PART TWO: PREDICTORS OF TREATMENT TIME WITH THE LIDCOMBE PROGRAM ................................................................................................ 117

Chapter 4: Predictor Study One.............................................................. 118

Introduction........................................................................................................119 Method ................................................................................................................122 Results .................................................................................................................127 Discussion............................................................................................................135

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Chapter 5: Predictor Study Two ............................................................. 139

Introduction........................................................................................................140 Method ................................................................................................................140 Results .................................................................................................................143 Discussion............................................................................................................150

PART THREE: RANDOMISED CONTROLLED TRIAL OF THE LIDCOMBE PROGRAM ................................................................................................ 154

Chapter 6: A Simulated Study of Analysis of the Primary Outcome Measure .................................................................................................... 155

Introduction........................................................................................................156 Methods...............................................................................................................169 Results .................................................................................................................172 Discussion............................................................................................................175 Conclusions .........................................................................................................181

Chapter 7: The Randomised Controlled Trial ........................................ 183

Introduction........................................................................................................184 Methods...............................................................................................................186 Conduct of the Trial...........................................................................................193 Results .................................................................................................................197 Discussion............................................................................................................205

PART FOUR: SUMMARY ......................................................................... 207

Chapter 8: Summary and Conclusions .................................................. 208

Summary of the Thesis ......................................................................................209 Conclusions .........................................................................................................212

References................................................................................................ 214

Appendices............................................................................................... 240

17

List of Tables

18

1.1 Mean number of disfluencies per 100 words of 68 stuttering boys

and 68 non-stuttering boys

28

2.1 Conditions under which Type I and Type II errors occur 55

2.2 Summary of 26 included studies in chronological order 62

3.1 Illustration of sample size (n) being inversely proportional to the

effect size (∆) squared

96

3.2 Approximate proportional increases in sample size required to

maintain power for compliance rates of c1 and c2

98

3.3 Details of papers dealing with stuttering published in the Journal

of Speech, Language and Hearing Research (Vol. 39, No. 1 to

Vol. 40, No. 4) and the Journal of Fluency Disorders (Vol. 21,

No. 1 to Vol. 22, No. 3)

100

3.4 The sample sizes required for different population standard

deviations and population mean subjective units of distress SUD

anxiety scores

112

4.1 Details of the 11 children who failed to complete Stage 1 123

4.2 Descriptive statistics on the 250 children who completed Stage 1 128

4.3 Results of univariate logistic regression of treatment time 131

4.4 Results of multivariate logistic regression of treatment time 131

5.1 Details of the 12 children who did not complete Stage 1 142

5.2 Descriptive statistics for the 66 children 144

5.3 Results of multivariate logistic regression of treatment time

(British data only)

145

5.4 Results of multivariate logistic regression of treatment time

(British and Australian data combined)

149

6.1 Power and Type 1 error for sample size of 50 in each group, with

expected mean and standard deviations 3.6 for Group 1 and 2.0

for Group 2

173

19

6.2 Power and Type 1 error for sample size of 20 and 50 in each

group, with expected mean and standard deviations 4.4 for Group

1 and 2.0 for Group 2

173

6.3 Power and Type 1 error for sample size of 20 in each group with

expected means and standard deviations 5.4 for Group 1 and 2.0

for Group 2

174

6.4 Power and Type 1 error for sample size of 20 and 5 in each

group, with expected mean and standard deviations 13.0 for

Group 1 and 2.0 for Group 2

174

6.5 Power and Type 1 error for sample size of 5 in each group, with

expected mean and standard deviations 20.0 for Group 1 and 2.0

for Group 2

175

7.1 Participants lost to follow up 199

7.2 Baseline characteristics of participants lost to follow up and

participants remaining on study

199

7.3 Treatment received 200

7.4 Baseline characteristics of all participants 202

7.5 Stuttering severity (%SS) at pre-treatment and 9-months post-

randomisation by treatment group

203

7.6 Comparison of stuttering severity (%SS) by treatment group at 9-

months post-randomisation

203

7.7 Stuttering severity (%SS) at baseline and 9-months by treatment

site

203

7.8 Number of participants achieving %SS of less than 1 at 9-months

post-randomisation

204

7.9 Estimates of treatment effect within subgroups 204

20

List of Figures

21

3.1 p-values for a measure of “quality of life” during the course of the

Bishop et al. (1999) study at the times that various numbers of

participants were recruited

108

3.2 p-values over the course of the Bishop et al. (1999) study for the

dependent variable “time to first treatment failure”

108

4.1 Number of clinic sessions required to complete Stage 1

133

4.2 Number of clinic sessions required to complete Stage 1 by gender 133

4.3 Number of clinic sessions required to complete Stage 1 by baseline

severity of stuttering

134

4.4 Number of clinic sessions required to complete Stage 1 by age 134

4.5 Number of clinic sessions required to complete Stage 1 by time

since onset of stuttering

135

5.1 Kaplan-Meier plot of number of clinic visits to complete Stage 1 146

5.2 Meta-analysis of time to complete Stage 1 by stuttering severity at

first clinic visit

147

5.3 Meta-analysis of time to complete Stage 1 by time from onset of

stuttering to treatment

148

5.4 Meta-analysis of time to complete Stage 1 by gender 148

5.5 Meta-analysis of time to complete Stage 1 by age 149

6.1 Distribution of %SS in a clinical caseload of English children 160

6.2 Distribution of %SS in a clinical caseload of Australian children 161

6.3 Distribution of %SS in a cohort of adult stutterers before treatment 161

6.4 Distribution of %SS in a cohort of adult stutterers after treatment 162

6.5 Normal Q-Q plot of %SS 164

6.6 Gamma Q-Q plot of %SS 165

6.7 Simulated gamma distribution 166

22

7.1 Recruitment over time 194

7.2 Flowchart of participants 198