Familial Childhood Stuttering: Stuttering Characteristics and Speech Abilities
Suzanne M. Buck1, Roberta Lees1, Peter Martin2, Alison Nicholas3 and Liz Hoey4
1Dept of Speech and Language Therapy, University of Strathclyde, 76 Southbrae Drive, Glasgow, G13 1 PP, UK
2Dept of Educational Studies, University of Strathclyde, 76 Southbrae Drive Glasgow, G13 1 PP, UK
3Michael Palin Centre for Stammering Children, Finsbury Health Centre, Pine Street, London, EC IR OLP, UK
4Speech and Language Therapy, Pollokshaws Clinic, 35 Well Green, Glasgow, G43 IRR, UK
Whilst research into family histories of stuttering is important, this has rarely been related to the implications for the child. This study explored familial childhood stuttering in contrast to childhood stuttering with no familial factor. Data are presented for 35 young children who stutter, of whom 25 had positive, and 10 had negative family histories of the disorder. These 2 subgroups were compared in terms of stuttering onset, disfluency types, and speech abilities. The results indicate that there are no differences in the stuttering characteristics of children who stutter, between those with and without familial histories of stuttering.
During the last century, there have been many attempts to understand the aetiology of stuttering but these have led to conflicting results. There is now a general consensus that the stuttering population is heterogeneous and so efforts to subgroup this population into relatively discrete groups would aid our understanding of the disorder. So far, no clear means of subgrouping the stuttering population has emerged (Buck, Lees & Cook, 2002). One way of doing this however, would be to subgroup on the basis of family history of stuttering as this may ultimately determine the existence of differences among children who stutter.
The fact that stuttering runs in families is frequently recorded (Kidd, 1985; Yairi et al., 1996). Bloodstein (1995) summarises that roughly 50% of people who stutter have histories of stuttering in their relatives. Further, Ambrose et al., ( 1993) found positive histories of stuttering in family members of 71% of young children who stutter. The evidence of heredity of stuttering is reasonably strong (Bloodstein, 1995) with models of genetic transmission being able to account for the patterns of stuttering observed in family pedigrees. Nevertheless, Yairi (1997) highlights that subgrouping of subjects on family history of stuttering has received very little attention. Whilst research into family histories of stuttering is important, this has rarely been related to the implications for the child, including his/her onset of stuttering, stuttering characteristics and speech abilities.
The age of onset of stuttering appears to be associated with stuttering chronicity. Yairi et al. (1996) found a later age of onset of stuttering to be related to persistence of the disorder. They did comment however, that this may have been partially due to the higher number of males in their persistent group, with boys having previously been found to have begun stuttering around 5 months later than girls (Yairi & Ambrose, 1992). Still, children that have a family history of stuttering may differ in their age of onset of the disorder from those with no family history. Such inquiry may have implications clinically in terms of prioritisation, should familial stuttering and a late age of onset be linked. 32 Theory, research and therapy in fluency disorders
School-aged children who stutter (aged 8-17 years) with positive family histories of stuttering have been found to exhibit a greater number of sound prolongations and blocks (J anssen, Kraaimaat & Brutten, 1990) compared with children with no such history. As their study involved older children, thus being biased towards chronicity, it remains unclear whether differences in disfluency types are evident between young children with negative and positive family histories of stuttering.
Paden et al. (1999) found that children who stutter and have additional speech difficulties are more likely to persist to stutter. Thus, children who stutter and have concomitantspeech difficulties may have a poorer prognosis for recovery from stuttering. Furthermore, Paden and Yairi (1996) hypothesise that speech difficulties and persistent stuttering may be genetically linked.
Louko et al. (1999) assert that speech difficulties are one of the most common communication problems to co-occur with stuttering. From examination of a number of studies, the prevalence of this co-occurrence ranges from around 16-67% (see Pellowski et al., 2001). As studies regarding stuttering and co- occurring speech difficulties have tended not to subgroup children who stutter, this may explain the great variety of reported percentages of children who stutter and have speech difficulties (Louko, 1995). Wolk et al. (1990) emphasise that understanding the co-occurrence of stuttering and speech difficulties has clinical implications, for example, differential diagnosis, with the possibility of behavioural subgroups of children who stutter.
Paden et al. (1999) investigated the speech difficulties of children whose stuttering persisted and those who recovered. At the initial assessment, the group who persisted to stutter exhibited poorer speech skills than did those who recovered from stuttering. Paden et al. (1999) assert that there is increasing evidence indicating that young children who stutter and have delayed speech development, are usually in the group whose stuttering will be persistent. They posit that genetic differences between those who recover or persist to stutter, may be reflected by differences in co- occurring speech difficulties.
Ehrig et al. (2000) report that where a child is late in developing linguistic competence, including speech skills, this is a predictor of decreased success in therapy. Whether or not the presence of co-occurring speech difficulties differs between children who stutter with or without family histories of stuttering requires investigation, particularly as they appear to coincide with persistent stuttering.
In summary, the current study explored familial childhood stuttering in contrast to childhood stuttering with no familial factor. Positive and negative family history subgroups of young children who stutter were compared in terms of stuttering onset, disfluency types, and speech abilities.
A total of 35 children aged 3;01 to 5,11 (years; months) participated in this study. For inclusion, each participant had to:
- have a weighted-stuttering-like disfluency score of 4 or greater (following Ambrose & Yairi, 1999), a parental severity rating of at least ‘mild stuttering’ and to be regarded as having a stuttering problem by the first author. '
- be a monolingual English speaker, and have no known or reported hearing impairment, neurological involvement, learning difficulties or oral structural abnormalities.
- have family information available from both genetic parents.
On meeting these criteria, the children were assessed in clinics, by the Speech and Language Therapists of 2 specialist disfluency teams. The children’s speech abilities were assessed using an UK standardised procedure (Edinburgh Articulation Test, Anthony et al., 1971). A story retell and 2 conversational tasks were undertaken with the children to elicit comprehensive samples for the disfluency analyses. Video-recordings of the children’s assessments were made for later transcription and analyses.
Data pertaining to stuttering onset was obtained during parent interviews, using structured questions and probes, as advocated by Yairi and Ambrose (1992).
The mother and father of each participant completed a family history questionnaire, providing full family pedigree information (child’s parents, grandparents, siblings, blood related aunts, uncles, and cousins) and details of any histories of stuttering and other speech and language difficulties for these relatives. The questionnaires were completed outside of the clinic, in order that parents could talk to their family members and provide as accurate information as possible. Further, the reliability of the family history data was established through the use of verification questionnaires, completed by additional family members. '
Phonetic transcription of the speech data, and the identification and classification of disfluencies, were undertaken in conjunction with the original video-recordings, with repeated reviewing as necessary, until confident in the judgements made. Standard scores for the articulation test were determined from the. phonetic transcriptions. The following disfluency counts were determined for each participant, per 100 syllables: total disfluencies, stuttering-like disfluencies, other disfluencies, and each specific disfluency type: part-word repetitions, single-syllable word repetitions, prolongations, blocks, broken words, interjections, revisions, and multisyllable word! phrase repetitions. Weighted scores for the stuttering-like disfluencies (SLD) were also calculated, following Ambrose and Yairi (1999). For the identification and classification of all disfluencies, inter- and intra-rater agreement levels were high, with Kappa values of 0.78 and 0.91 respectively. The percentages of point-by-point inter- and intra-rater agreement for the phonetic transcription of the speech data were also high, with means of 89.6% (range = 87.9%-90.8%) and 95.4% (range = 93.7%~96.4%) respectively. All of these analyses were performed blind to the family history status of the participants.
The questionnaire data were analysed to determine the family history status of each participant. Participants for whom the parents reported no histories of stuttering in first-, second- and third- degree blood relations (i.e. parents, siblings, grandparents, uncles, aunts and cousins) constituted the negative family history (NFH) subgroup (N = 10, 28.57% of the sample). Participants with reported histories of stuttering in 1 or more first-, second- and third-degree relatives comprised the positive family history (PFH) subgroup (N = 25, 71.43% of the sample).
The NFH and PFH subgroups were found to be homogeneous with respect to chronological age and time since onset. The NFH subgroup had a higher number of males to females (8:2) than the PFH subgroup (13:12), though this difference was not statistically significant (Fisher, p = 0.38).
Age of reported onset of stuttering
The mean reported age of onset of stuttering was 32.70 months (SD = 6.53) for the NFH subgroup and 32.13 months (SD = 9.46) for the PFH subgroup. Thus, the difference between the mean reported age of onset for the NFH and PFH subgroups was not statistically significant (t = 0.17, df = 31, p = 0.86). Additionally, the boys began stuttering ‘on average only around 2 weeks later than the girls.
Many of the distributions for the disfluencies exhibited were skewed. Medians are therefore given, providing more representative measures of central tendency. The median total, stuttering-like and other disfluencies exhibited by the NFH and PFH subgroups and their weighted-SLD scores are presented in Figure 1. It should be noted that the total disfluencies bars do not directly represent the summation of the bars for the stuttering-like and other disfluencies in Figure 1, but rather, the subgroup medians for each comparison are displayed. The medians for the individual stuttering- like disfluency types: part-word repetitions (PWR), single-syllable word repetitions (SSWR), prolongations (Prol), blocks (B), broken words (BW), and other disfluency types: interjections (I), revisions (R) and multisyllable word/phrase repetitions (MS/PR), are given in Figure 2.
Figure 1. Median disfluencies exhibited by the NFH and PFH subgroup participants, per 100 syllables.
Figure 2. Median disfluencies exhibited by the NFH and PFH subgroup participants, per 100 syllables
Visual inspection of the results presented in Figures 1 and 2 reveal that slightly higher values were found for the NFH subgroup for the total disfluencies and more specifically, for each of the types of stuttering-like disfluencies, compared with the PFH subgroup.
Inferential statistical analyses using Mann Whitney U tests revealed no statistically significant differences between the NFH and PFH subgroups in the total numbers and specific types of disfluencies exhibited. It should be pointed out that there were so few instances of blocks and broken words in particular, that applying statistical analyses to these was not very meaningful. Nevertheless, the data for these comparisons are included for completeness.
The mean standard scores obtained on the Edinburgh Articulation Test (Anthony et al. 1971) were 105.50 (SD = 18.93) for the NFH subgroup (N = 10) and 107.87 (SD = 15.69) for the PFH subgroup. The difference between these mean standard scores was not statistically significant
(t = -0.38, df = 31, p = 0.71).
Further, only 4 participants were identified as having speech difficulties according to their standard scores on this test (<85). These participants comprised 2 each from the NFH and PFH subgroups.
The percentage of participants with positive family histories of stuttering (71.43 %) was much higher than the summary of around 50% given by Bloodstein (1995), but highly comparable with the finding of 71% for young children reported by Ambrose et al. (1993).
The higher ratio of males to females within the NFH subgroup found in the present study is consistent with a prior study by Buck et al (2002). Although statistical significance was not reached, these 2 studies do not support the finding of a higher proportion of males to females within the positive family history group, reported by Ambrose et al. (1993).
The mean age of reported onset of stuttering of around 32 months found in this study is highly comparable with previous mean onset ages of 32.76 months (Yairi & Ambrose, 1992) and 36.3 months (Buck et al., 2002). The finding of no difference in the mean reported ages of onset of stuttering between the NFH and PFH subgroups suggests that onset age is not related to familiality of the disorder. As a later onset of stuttering has previously been found to be associated with persistent stuttering (Yairi, Ambrose, Paden et al., 1996), neither of the family history subgroups would appear to be at greater risk for persistence in terms of having significantly later reported ages of onset of stuttering.
Participants with negative family histories of stuttering exhibited a few more disfluencies overall. However, the findings of this study clearly reveal that the individual frequencies and types of disfluencies exhibited by young children who stutter do not vary with familial history of stuttering. This would suggest that the characteristics of stuttering, in terms of disfluencies produced, are independent of familiality of stuttering. Furthermore, as the weighted-stuttering-like disfluency scores, which provide a measure of stuttering severity (Ambrose & Yairi, 1999), did not differ significantly between the family history subgroups, severity would also appear to independent of farniliality.
The participants in this study attained unexpectedly high mean standard scores on the articulation test. The subgroups of young children who stutter with negative and positive family histories of stuttering did not differ with respect to their speech abilities, as measured on a standardised articulation test. As concomitant speech difficulties and persistent stuttering have previously been found to be linked (Paden et al., 1999), the NFH and PFH subgroups would appear to be at equal risk for persistence in terms of having highly similar speech abilities. The finding of only 4 young children who stutter to have co-occurring speech difficulties was very low, particularly given that stuttering and speech difficulties have frequently been reported to co-occur (Louko et al., 1999; Pellowski et a1., 2001). Nevertheless, speech difficulties were found for participants from both subgroups. These findings lend no support to the postulation by Paden et al. (1999) that genetic differences may be reflected by differences in co-occurring speech difficulties. In fact, the participants in the PFH subgroup actually had slightly more advanced speech abilities than did the NFH subgroup participants, though the difference was nonsignificant.
In summary, the findings of this study indicate that whether children do or do not have a familial history of stuttering fails to help distinguish them in terms of their early stuttering development, when one looks at the characteristics such as age of onset, disfluency types, and speech abilities. In future studies, rather than the paradigm of contrasting NFH and PFH subgroups, perhaps the stuttering characteristics should be examined between those with positive family histories of recovery or persistence, or between NFH subgroups and those with histories of stuttering in their first-degree relatives, or high-density family histories of stuttering. 36 Theory, research and therapy in fluency disorders
The first 2 authors wish to thank the Royal College of Speech and Language Therapists and the University of Strathclyde for financial assistance towards attending the Congress.
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