How common isspecific language impairment (SLI)? Dorothy V M Bishop
Our best estimate of frequency of SLI = 3%• This corresponds to around One child in every classroom• But the number is not set in stone and will vary from place to place and according to definition• So you may hear very different numbers reported• Here we’ll present some of the evidence behind the numbers
SLI is identified when• Child’s language ability is well below age level• Language problems aren’t explained in terms of known causes such as hearing loss, autism, general intellectual retardation• Language problems interfere with everyday life at home and /or school
Numbers with SLI will depend on precise definition• Child’s language ability is well below age level• Not explained by other factors All these terms can be interpreted in different ways
Study conducted in Mannheim, Germany• 320 children after excluding those with hearing loss or autism• N.B. Selected to represent range of levels of biological and environmental risk• Seen at 4.5 yr and 8 yr for assessments of expressive and receptive language* and nonverbal ability*One expressive, one receptive subtest from Illinois Test of Psycholinguistic abilitiesWeindrich, D., Jennen-Steinmetz, C., Laucht, M., Esser, G., & Schmidt, M. H. (2000).Epidemiology and prognosis of specific disorders of language and scholastic skills.European Child and Adolescent Psychiatry, 9(3), 186-194.
Strict definition of SLICriteria of International Classification of Diseases,ICD-10a)Performance on language test 2 SD or more belowgroup mean (i.e. in bottom 3%)b)Language score at least 1 SD below nonverbal IQscorec)Nonverbal IQ at least 70
Strict definition of SLI ICD-10 criterion a)Performance on language test 2 SD or more below group mean (i.e. in bottom 3%) b)Language score at least 1 SD below nonverbal IQ score c)Nonverbal IQ at least 70Criterion met by•7 children (2.2%) at 4.5 yr•3 children (1%) at 8 yr
Clinical definition of SLIICD-10 criterion widely viewed as arbitrary and notmapping on to clinical needTherefore developed a clinical definition that relaxedthe severity of language impairment requireda)Performance on language test 1.5 SD or more belowgroup mean (i.e. in bottom 7%)Other ICD10 criteria were retained
Clinical definition of SLIa) Performance on language test 1.5 SD or more below group mean (i.e. in bottom 7%)b) Language score at least 1 SD below nonverbal IQ scorec) Nonverbal IQ at least 70 Criterion met by •14 children (4.3%) at 4.5 yr •11 children (3.4%) at 8 yr (N.B. includes those meeting ICD10 criteria)
Least strict definition of SLINonspecific language impairmentRemove need for mismatch between language and IQ.Child just has to show:a)Performance on language test 1.5 SD or more below groupmean (i.e. in bottom 7%)b)Nonverbal IQ at least 70Criterion met by•21 children (6.6%) at 4.5 yr•11 children (3.4%) at 8 yr(N.B. includes those meeting ICD10 and clinical criteria)
More children included ascriteria become less stringent Strict ICD10 Clinical Nonspecific Language Impairment
Frequency of SLI will also vary from population to population• Most studies find more common in boys than girls (though will depend on definition)• In some children problems resolve with age, so fewer older children meet criteria for SLI• Mannheim study found SLI more common when there was either biological risk (low birth weight and/or preterm birth) or psychosocial risk (range of family factors, including parental age, education, income, etc).
A complication: Speech problems• Many studies combine speech and language problems into a single category• Speech problems involve difficulties articulating all the sounds of the language and are quite common in preschool children• Speech problems can co-occur with language problems, but often they occur in isolation• Speech problems are a common reason for a young child to be referred for speech and language therapy
Some other relevant studies• Stevenson & Richman (1976) 3 yr olds in UK; delayed language development in 3.1%, but most with low nonverbal ability; Specific language delay in only 0.57%• Beitchman et al (1986), 5-year-olds in Ottawa; 12.5% had language problems (No nonverbal assessment)• Tomblin et al (1997) 6-year-olds in US mid-West; 7.4% had SLI (but only 29% had been identified as in need of services)
Impact of language impairment on everyday life• Most studies that estimate frequency of SLI have relied just on language test scores• Ideally should also consider impact on child’s everyday life at home and school• Language tests may miss key aspects of communication problems (especially if only a short test battery is used)• But also, some children with low language test scores may actually function well at home and school• Parent or teacher report should supplement tests to give a fuller picture
Study using parent/teacher report• Longitudinal Australian Cohort Study: representative sample of 4983 children aged 4 to 5 years• 25% parents concerned about how child talked and made speech sounds (but this includes articulation)• 9% parents concerned about language understanding• Teacher concern about expressive language in 22% and concern about comprehension in 17%• But N.B. parent concern only weakly related to language test scores• 10% accessed a speech-language therapist over past 12 moMcLeod, S., & Harrison, L. J. (2009). Epidemiology of speech and language impairmentin a nationally representative sample of 4-to 5-year-old children. Journal of Speech,Language, and Hearing Research, 52(5), 1213-1229.
Best estimate of frequency of SLI = 3%• But overall, general convergence from studies that this is reasonable estimate of proportion of children with language problems severe enough to affect their social interaction with others and/or their success at school, and which have no known cause• RALLI exists because we think that many people aren’t aware of SLI, even though it is a common childhood condition that has real effects on children’s lives• PLEASE HELP SPREAD THE WORD BY PUBLICISING OUR CHANNEL: http://www.youtube.com/RALLIcampaign/
For references related to this talk please see http://www.slideshare.net/RALLICampaign/how- common-is-sli andhttp://www.slideshare.net/RALLICampaign/how-is-specific-language-impairment-identified-13957123