Epidemiological advances in stuttering during the current century are reviewed within the perspectives of past knowledge. The review is organized in six sections: (a) onset (b) incidence (c) prevalence (d) developmental paths, (e) genetics and (f) subtypes. It is concluded that: (1) most of the risk for stuttering onset is over by age 5, earlier than has been previously thought, with a male-to-female ratio near onset smaller than what has been thought, (2) there are indications that the lifespan incidence in the general population may be higher than the 5% commonly cited in past work, (3) the average prevalence over the lifespan may be lower than the commonly held 1%, (4) the effects of race, ethnicity, culture, bilingualism, and socioeconomic status on the incidence/prevalence of stuttering remain uncertain, (5) longitudinal, as well as incidence and prevalence studies support high levels of natural recovery from stuttering, (6) advances in biological genetic research have brought within reach the identification of candidate genes that contribute to stuttering in the population at large, (7) subtype-differentiation has attracted growing interest, with most of the accumulated evidence supporting a distinction between persistent and recovered subtypes.

Although the past 50 years of research on early childhood stuttering and normal disfluency have produced vital information on the general features of disfluent speech behavior of young children, an adequate normative reference for early stuttering does not exist. The purpose of this report is to provide such reference and to provide a basis for clinical needs of differential diagnosis of stuttering from normal disfluency. Data are presented from 90 stuttering children ages 2 to 5 within 6 months of stuttering onset and from 54 age-matched normally fluent children. Means for disfluency types are presented. No significant differences were found for gender or for age. Stuttering-like disfluencies (SLD) did differ significantly for the stuttering and fluent groups, but other disfluencies (OD) did not. A weighted SLD is defined to further clarify differences between the groups. The pattern of disfluency types for normally fluent and for mild, moderate, and severe stuttering is presented. Stuttering is shown to be qualitatively as well as quantitatively different from normal disfluency even at the earliest stages of stuttering. Clinical and research implications are discussed.

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Both clinical and theoretical interest in stuttering as a disorder of speech motor control has led to numerous investigations of speaking rate in people who stutter. The majority of these studies, however, has been conducted with adult and school-age groups. Most studies of preschoolers have included older children. Despite the ongoing theoretical and clinical focus on speaking rate in young children who stutter and their parents, no longitudinal or cross-sectional studies have been conducted to answer questions about the possible developmental link between stuttering and the rate of speech, or about differences in rate development between preschool children who stutter and normally fluent children. This investigation compared changes in articulatory rate over a period of 2 years in subgroups of preschool-age children who stutter and normally fluent children. Within the group of stuttering children, comparisons also were made between those who exhibited persistent stuttering and those who eventually recovered without intervention. Furthermore, the study compared two metrics of articulatory rate. Spontaneous speech samples, collected longitudinally over a 2-year period, were analyzed acoustically to determine speaking rate measured in number of syllables and phones per second. Results indicated no differences among the 3 groups when articulation rate was measured in syllables per second. Using the phones per second measure, however, significant group differences were found when comparing the control group to the recovered and persistent groups.

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Although past research has provided evidence of a genetic component to the transmission of susceptibility to stuttering, the relationship between the genetic component to stuttering and persistence and recovery in the disorder has remained unclear. In an attempt to characterize this relationship, the immediate and extended families of 66 stuttering children were investigated to determine frequencies of cases of persistent and recovered stuttering. Pedigree analysis and segregation analysis were used to examine patterns of transmission. The following questions were investigated: 1. Is there a sex effect in recovery from stuttering? Here, we sought to test the hypothesis that females are more likely to recover than males, leading to the change in sex ratio from approximately 2:1 males to females close to onset of the disorder, to 4 or 5:1 in adulthood. 2. Is persistence/recovery in stuttering transmitted in families? If recovery/ persistence appears to be transmitted, (a) are recovered and persistent stuttering independent disorders?; (b) is recovery a genetically milder form of persistent stuttering?; or (c) is persistence/recovery transmitted independent of the primary susceptibility to stuttering? Results indicated sharply different sex ratios of persistent versus recovered stutterers in that recovery among females is more frequent than among males. It was found that recovery or persistence is indeed transmitted, and further, that recovery does not appear to be a genetically milder form of stuttering, nor do the two types of stuttering appear to be genetically independent disorders. Data are most consistent with the hypothesis that persistent and recovered stuttering possess a common genetic etiology, and that persistence is, in part, due to additional genetic factors. Segregation analyses supported these conclusions and provided statistical evidence for both a single major locus and polygenic component for persistent and recovered stuttering.

A nationwide survey of pediatricians was conducted to assess their practices with and attitudes and beliefs about young children who stutter and their stuttering. Data obtained from 439 respondents were analyzed. The findings indicated mixed trends. Although the opinions of the majority of the pediatricians agreed with current information about stuttering, on several important matters a significant percentage held outdated or erroneous beliefs about the etiology of the disorder or characteristics of young children who stutter. Beliefs about etiology appeared to influence opinion of treatment choice with a strong tendency for delaying intervention and a preference for parent-oriented intervention. Respondents were inconsistent in their interpretation of early diagnostic signs of stuttering. Interest among pediatricians in obtaining updated information about stuttering was strong. Practical implications for speech-language pathologists are discussed.