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JCPSLP
Volume 18, Number 2 2016
Journal of Clinical Practice in Speech-Language Pathology
allowing for the interpretation of data from large bodies of
information (Petticrew & Roberts, 2006).
Predictive factors for stuttering
treatment
Findings from systematic reviews
There is much to learn from investigating the predictive
factors of stuttering treatment outcomes. With improved
measures of treatment outcomes encompassing the impact
of stuttering on an individual’s quality of life, as well as the
more reliable identification and measurement of relevant
client and clinician factors, it may be possible one day to
develop predictive models of treatment success.
Previous systematic reviews of stuttering treatment
include one by Bothe, Davidow, and Bramlett (2006). They
conducted a qualitative systematic review of behavioural,
cognitive, and related approaches to stuttering therapy
across a range of age groups. The prolonged speech
approach, treatment targeting self-management, and
treatment using response contingencies were found to
have the strongest evidence for adults who stutter (AWS).
For early stuttering, the authors concluded response-
contingent-based therapies had the strongest evidence.
Herder, Howard, Nye, and Vanryckeghem (2006)
reported results from a systematic review and meta-
analysis of behavioural stuttering treatments and concluded
that treatments resulted in positive therapeutic gains, but
there was no one treatment approach that was significantly
better than the others. Subsequently, a systematic review
by Nye and colleagues (2013) reported that the current
best evidence for children who stutter up to 6 years of age
was the Lidcombe Program (LP) developed by Onslow
and colleagues. Of these systematic reviews of treatment
in stuttering, none specifically addressed predictive factors
of treatment outcomes. Nevertheless, the importance of
finding out more about predictive factors was recognised
(Herder et al., 2006; Nye et al., 2013). Nye et al. (2013)
further acknowledged that there were limited data available
to make any useful conclusions.
Herder et al. (2006) noted a lack of understanding of
how each factor or sets of factors may impact on treatment
outcome. Interestingly, they concluded that differences in
the effectiveness of intervention approaches were unlikely
due to the nature of the intervention strategies themselves
or to participant characteristics. Instead they hypothesised
that clinician impact could have played a role, stating that
“it might well be that the clinician represents a helping
individual who is perceived to have the knowledge and skills
to bring about a change in the speech behavior of a person
who stutters” (Herder et al., 2006, p. 70).
Adults who stutter
Results from the systematic reviews demonstrate that
treatment for stuttering is generally beneficial. However,
predicting which individuals will benefit most, as well as
knowing how to support those who may have higher risk of
regression, is a pivotal for clinicians prior to commencing
intervention. The potential to relapse is of interest and
concern in the provision of treatment to AWS, with up to
72% of adults relapsing post-treatment (Craig, 1998).
Relapse is defined as “stuttering to a degree which was not
acceptable to yourself for at least a period of one week”
(Craig, 1998, p. 3).
Stuttering severity
The definition of a predictive factor provided at the
beginning of this review stated that it relates to client
Age at onset
Yairi et al. (1996), in comparing groups of children who
recovered from stuttering with those whose stuttering
persisted, reported that children who continued to stutter
started stuttering 5 to 8 months later (onset at 39 months
of age) than those who recovered (onset from 30 to 33
months of age).
Time since onset
The time since onset of stuttering has been found to be a
prognostic factor for persistent stuttering, with the risk of
persistent stuttering being greater in individuals who have
been stuttering for more than one year than in those who
have not (Ambrose & Yairi, 1999).
Neurology
Chang and Ludlow (2010) reported further neurological
data to identify factors of persistence. Specifically, children
who had a persistent stutter had reduced white matter
integrity in the left hemisphere areas of the brain involved in
speech compared to those who recovered.
Language ability
There are inconsistent findings for status of speech and
language skills in predicting persistence of stuttering. For
example, Yairi et al. (1996) reported that better speech and
language skills may be related to recovery from stuttering,
whereas Watkins and Yairi (1997) found that children whose
stuttering persisted had typical to advance language skills.
Additional factors
Other behavioural factors that have been found to be
different between children with persistent stuttering and
children who recovered include differences in second
formant transitions (Subramanian, Yairi, & Amir, 2003),
higher variability of articulation rate for persistent stuttering
(Kloth, Kraaimaat, Janssen, & Brutten, 1999), and poorer
phonological and speech production abilities for persistent
stuttering (Spencer & Weber-Fox, 2014). Howell and Davis
(2011) found that symptom severity, as measured by the
Stuttering Severity Index, of children who stutter at 8 years
old was the only significant factor that was able to predict
persistence of stuttering in the teenage years using logistic
regression analysis. However, Yairi and colleagues (1996)
did not find that initial stuttering severity predicted
persistence in their study of younger children (under 6
years).
Interpreting risk and prognostic factors
In summary, common prognostic factors of stuttering onset
and of persistent stuttering include positive family history of
stuttering and age. An older child has less risk of stuttering
onset, though if a child is older when onset does occur, the
risk for the stutter to be persistent is higher. Additional
factors associated with persistent stuttering (i.e.,
behavioural factors) have been identified; however, caution
is required when interpreting such findings. For example,
replication of findings is needed to establish reliable
indicators of persistence, since current results are based
predominantly on single or few studies, with many having
small sample sizes (e.g., Chang et al., 2005,
n
= 14). A
number of studies are retrospective in design and it is
recommended that prospective studies are more
appropriate to answer questions of prognosis (Moons et al.,
2009). While there have been comprehensive reviews of
prognostic factors of stuttering onset and persistence, none
were systematic reviews. A systematic review would
synthesis and evaluate available information on this topic