Research on Incidence and Prevalence of Stuttering

By Ehud Yairi, Ph.D., University of Illinois
Summer 2005

In a recent conference on stuttering sponsored by the National Institute on Deafness and Other Communication Disorders (NIDCD), I discussed several factors related to predisposition to stuttering.  These include (a) occurrence, (b) age, (c) gender, (d) genetics, (e) stressors, (f) concomitant disorders, (g) persistency-recovery, and (h) subtypes.

Of these, I would like to summarize here a few observations pertaining to the issue of occurrence, that is, how many people stutter.

Whereas dry statistical data do not commonly excite the imagination of either researchers or clinicians, such information tells a whole lot about a particular disorder and often has significant influences on public interest, budgetary decisions for research and services, and professional training.

Thus, in my view, the prevailing "knowledge" that "only" 1% of the population stutters has created for us noticeable public perception problems as well as unwarranted attitude in the field of communication disorders. Specifically, the 1% figure has produced an incorrect impression that stuttering is a "small" problem.  It has been an important reason why, for a long period, the American Speech-Language-Hearing Association (ASHA) and many universities de-emphasized academic and clinical training in fluency disorders required of students specializing in speech-language pathology.

Although the prevalence of stuttering (how many people stutter at a given point in time) appears to be somewhat lower than 1% (about .73% according to Craig et al., 2002), the actual incidence (how many people have ever stuttered in their life) is approximately 5%, with onsets occurring mainly at the preschool age (Andrews & Harris, 1964; Manson, 2000).   Furthermore, it is important to realize that the 1% prevalence is an average for the population at large.

Therefore, it is equally important to understand that the prevalence varies greatly according to age groups.  A recent individual screening study we conducted with more than 3,000 preschool children revealed a 2.43% stuttering prevalence with no racial or ethnic differences (Proctor et al., 2002; Yairi & Ambrose, 2005 ).

If the findings are valid, they mean that at any point in time up to almost 2.5% percent of children under age 5 stutter.  In other words, at any time, in spite of a high level of natural recovery, a substantial number of preschoolers and their parents may be needing professional evaluation, counseling, and, sometimes, also therapy.

An important conclusion is that more resources should be directed to research concerning this sub-population.  Another lesson is that better preparation of speech-language clinicians for dealing with this substantial group of speech handicapped children should receive a higher priority.

To this end, all interested parties: scientists, clinicians, consumers of services, and private organizations, such as The Stuttering Foundation, should strive to alter the perception that stuttering is a "small" problem.  Using various public and private resources, this message should be taken to Congress, NIDCD, ASHA, and educational programs in speech-language pathology.


  • Andrews, G., & Harris, M. (1964). The syndrome of stuttering, Clinics in developmental medicine, No. 17. London: William Heineman Medical Books Ltd.
  • Craig. A, Hancock  K, Tran. Y, Craig. M, & Peters, K. (2002).   Epidemiology of stuttering in the communication across the entire life span. Journal of Speech Language Hearing Research, 45:1097-1105.
  • Mansson, H. (2000). Childhood stuttering: Incidence and development. Journal of Fluency Disorders, 25, 47-57.
  • Proctor A., Duff, M.. and Yairi, E. (2002). Early childhood stuttering: African Americans and European Americans.  ASHA Leader, Vol. 4, # 15, 102.
  • Yairi, E., & Ambrose, N.  (2005).  Early childhood stuttering.  Austin, TX: Pro-Ed, Inc.