Participants and sub-groups
A total of 317 children who stuttered participated. They all (a) started school in the UK at age 4 or 5, (b) first presented at a clinic when aged between 8 and 10 years and (c) lived in the greater London area. Stuttering was confirmed by a specialist speech-language therapist at the clinic. Reported onset of stuttering usually occurs before age 6. The attendance at clinic 2 or more years later is partly due to the time needed to process children in the health system; these are secondary referrals to the specialist clinic and devolved budgets to local area health authorities can cause delay. Recordings were taken to estimate the percentage of stuttered syllables and to allow the stuttering severity instrument measure SSI-33
to be applied (see below for details of how SSI-3 was calculated).
When each child was seen initially, all 317 caregivers were asked whether they used a language other than English exclusively or sometimes in the home. In cases where use of a second language other than English was reported, the caregivers had a further interview. When the caregiver did not speak English, help with translation was obtained from a close friend who spoke the same language as well as English. The interview obtained background details about the child, the family and information about languages used in the home. Details were collected about the biological relationship of the caregiver to the child (all were parents of the child they cared for). Data on gender and age at onset of stuttering were obtained. The child’s Standard Attainment Test educational scores (SATS) at ages 7 and 11 (key stages one and two) were obtained for English, mathematics and science. It was also established whether the caregiver spoke English to the child from birth up until the child went to school, and whether care was given by this person exclusively or some of the time up to age 5 years. The caregivers indicated whether the child spoke English when they entered school. Information was obtained about where the child was born and, in cases where the child was an immigrant, the age at which they had entered the UK and their language use in their former country. This language information was used to classify children as LE or BIL.
There were 69 cases where at least one language other than English was spoken in the home. Caregivers of 38 of those 69 children reported that they primarily or exclusively used a language other than English in the home and had done so since the birth of their child. This criterion excluded people who opted to speak a language other than English in the home for their child’s educational/social advancement. All 38 families have continued to participate. Nine of the group of 38 have not yet reached 12 years, leaving 29 who were categorised as recovered from stuttering or not.
The 38 selected children were divided into LE and BIL groups. The LE children may be regarded as not being bilingual until the age of school onset. The LE group consisted of 15 children (39.5% of the 38 children) who did not speak English when they started school. During this period, English was not used by the caregivers, English-language media were not accessed in the home and if there were siblings, they did not speak English up to the age of school entry.
Twenty three (60.5%) of the children spoke English in addition to the primary language spoken in the home (BIL group). They were all exposed to English in the home from birth.
A group of monolingual English speaking children who stuttered (MONO) was selected in order to assess the impact stuttering has on epidemiology and education and to determine how the stuttering severity of the MONO group compared with that of the experimental groups. The MONO children were selected at random from the entire sample of such children referred to the clinic, subject to the restrictions that the group had to match the LE and BIL groups for age and gender. They had similar socio-economic backgrounds and attended similar schools to the LE and BIL children.
When children in all groups passed 12 years of age, they and their families were interviewed about their stuttering and school record, and the children were recorded so that a stuttering severity measure could be obtained (to confirm whether or not their stuttering had continued).
A second control group of fluent children who used a language other than English in their pre-school years was recruited (fluent bilingual, termed FB). These children were age-matched to those children who stuttered at second attendance, so that SATS scores could be compared. The children were recruited from schools in the same catchment areas as the clinics and they had similar educational and socio-economic backgrounds as the LE and BIL children, and reported no history of speech/hearing problems. They were divided into LE and BIL groups using the same criteria as above. Data from the LE and BIL groups of FB children were used to compare educational attainment levels with those obtained for LE and BIL children who stuttered.
Classification as persistent/recovered
Stuttering was reassessed when the child was seen at age 12 plus by (a) the child, (b) the caregiver and (c) a researcher (the same for all children). All the scales used in these assessments have been normed (a statistical concept in psychometrics) (see supplementary data available online). The child questionnaire and the researcher report forms are given as supplementary material (the parent questionnaire was the same as the child questionnaire except that statements were changed from the first to the third person). For the child and caregiver, seven of the 15 questions on Boberg and Kully’s questionnaire4
were employed, and a further question was constructed which combined three more of their questions. For each of the eight questions, the child or caregiver indicated the extent of agreement on a five-point scale. Each question was scored 1–5, where 1 represented fluent behaviour and 5 dysfluent behaviour. The scores across all questions were summed, the maximum score being 40. Scores lower than 21 were considered “recovered” and scores greater than 21 were considered “persistent”. The scores on these questionnaires were correlated with SSI-3 scores as a validation criterion (part of the norming procedure described in the supplementary data). This showed that these cut-offs divided stutterers at the low end of the moderate scale (stuttering could not be moderate to have recovered and had to be at least moderate to be designated persistent).
The researcher visited each child’s home and recorded an interview that lasted approximately 90 min. During this visit, the researcher talked with a caregiver and the child about the speech problem and their experience in the clinic. He also sought their views about communication style and self-confidence in a range of typical environments. These included home and social gatherings with adults and children in and out of school. Performance and experience in school were assessed in terms of inter-personal relationships with staff and other children (including bullying). General health issues were also examined, including frequent absence from school and childhood illnesses. The researcher subsequently assessed speech fluency, social-conversational skills, and whether the child had a positive self-image/confidence about speech, using the recordings and notes taken at the home visit. Each of the three assessments was scored on a scale of 0 (good) to 3 (poor). The scores for the three factors were summed to give one score of between 0 and 9. A score of 5 or above indicated still stuttering.
To be designated as persistent, the caregiver, child and researcher all had to rate the child as still stuttering. To be designated as recovered, the caregiver, child and researcher all had to designate the child as not stuttering. All cases were unambiguously classified on all three criteria.5–8
All participants have been followed up for a minimum of 12 months and substantially longer in some cases (the mean length of follow-up for all speakers is 31.5 months with an SD of 24 months). The recovered participants showed no relapse and none of the participants designated as “persistent” recovered during this period.
The percentage of syllables stuttered out of the total syllables spoken in a 2 min recording of spontaneous speech made on the second occasion when the child was aged 12 plus was used to further check persistence/recovery. All recovered stutterers had fewer than 4% stuttered syllables, whereas all persistent stutterers had more than 4% stuttered syllables. Yairi and Ambrose reported that 3% stuttered syllables distinguished most speakers who stutter from fluent controls.9
From this, the recovered stutterers can be considered to be close to fluent whereas the persistent stutterers cannot.
Stuttering severity assessment (SSI-3)
The SSI-3, a standard measure of stuttering severity, was administered when the child was first seen and again at age 12 plus.3
The assessments were always conducted on samples spoken in English, including samples from two children who did not stutter in English but did in their first language. This was because SSI-3 is not available for those children’s first languages and no norms exist. For SSI-3, a monologue, a dialogue and a text, all of which contained at least 200 syllables, were recorded using a Sennheiser K6 microphone and a Sony DAT recorder. Associated physical concomitants such as tics and twitches were noted. SSI-3 scores were obtained by qualified personnel.
SPSS 11.0 (release 11.5.0; SPSS, Chicago, IL) was used for the descriptive analysis and for the non-parametric χ2 tests. For parametric measures either independent t tests (SATS performance categories) or ANOVA (age at onset, SATS absolute scores and SSI-3 scores) were used for assessing differences between groups. For the parametric measures, 95% confidence intervals were calculated and p<0.05 was considered to be significant.
Ethics approval was obtained from the UCL Committee on the Ethics of Non-NHS Human Research (project ref 0754/003).