The origins, outcomes and impact of persisting phonological impairment

Lead Research Organisation: University of the West of England
Department Name: UNLISTED


Children with speech difficulties form the largest group of those referred to children?s speech and language therapy departments. Though some children grow out of their difficulties, others have persistent problems that can affect their educational progress and social development.
Previous research into children?s speech impairments has been unable to agree on the percentage of the population who are affected by this. In addition, a number of factors such as intelligence and family factors have been found to be associated with speech impairment though there is no conclusive agreement on which factors are most important. Similarly, the degree to which educational and social development is affected is in dispute.
Some speech impairments are associated with anatomical or neurological impairments such as cleft palate or cerebral palsy, but for a large number of children, there is no identifiable cause. Research has suggested many possibilities and it is also thought that different subgroups may exist.
Some of the research on speech impairments is now outdated and uses definitions of speech impairment that are no longer accepted. With the more recent studies, there has been a tendency to use small samples of children, in some instances just one or two cases. There is therefore an urgent need for population-based research.
The Avon Longitudinal Study of Parents and Children (ALSPAC) is a large scale study of children?s development which has collected information on children?s speech development at ages 2, 5 and 8. This provides a unique opportunity to investigate some of the questions surrounding speech impairment. The proposed study will identify the percentage of children aged 5 and 8 years who have speech impairments, what factors predict persistent problems and what factors are associated with a good prognosis . It will identify outcomes for children with speech impairments and investigate the existence of any subgroups.

The researcher team have considerable expertise in the field of children?s speech impairment as well as being familiar with the data collected in the ALSPAC study.

Findings from this study will support the early identification of children at risk of persisting speech impairments and help to identify interventions which may prevent long term negative outcomes. In addition, a clear understanding of the numbers affected by these difficulty together with information on the factors which are associated with it, will enable services to be planned more effectively and resources targeted where they are most needed.

Technical Summary

Children with speech impairments (SI) form the largest group of children referred to speech and language therapy. However, our knowledge of the origins, nature and outcomes of SI lacks coherence; services and therapists therefore have limited knowledge upon which to base decisions.

Research literature reports varying prevalence rates for SI. This arises because of the differing definitions used and the various ages at which prevalence has been investigated. Many factors have been identified in younger children that could be used to predict SI but these are based on studies that are either dated or use small samples. There is also ongoing debate about the educational outcomes and social impact for children with SI. The presence of possible subgroups has been proposed but not validated in large-scale studies.

The Avon Longitudinal Study of Parents and Children is a population-based study that has collected wide-ranging data about the children?s cognitive, social, emotional and physical development. The study has also sampled speech data from the children at the ages of 2, 5 and 8 years. The study therefore provides a unique opportunity to investigate the nature of SI in children.

The aims of the research are to establish prevalence figures for SI in 5 and 8 year olds, to identify predictive factors and outcomes, to describe the profile of the children with SI in terms of language, cognitive and motor skills and to investigate the existence and nature of subgroups of speech problems.

Children will be categorised as either case or control children using algorithms for the identification of SI and the measure of Percentage of Consonants Correct. Following descriptive analysis of putative variables, data for case and control children will be compared using a series of logistic regressions to identify predictive factors, outcomes and co-morbidity. Prevalence figures at each age would be calculated using 95% confidence intervals and the existence of subgroups based on surface phonological patterns will be investigated.

The research team are familiar with the ALSPAC data set and have successfully collaborated on a variety of projects regarding children with speech and language impairments.

The importance of children?s speech and language development to their future educational and social success has attracted increasing attention in government policy. However, the amount of speech and language therapy available is also of concern. Access to improved research data about the nature and outcome of SI is crucial to effective targeting of therapy resources.


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