Epidemiological data From: Jonathan Bashor Date: 10/3/99 Time: 9:37:00 AM Remote Name: 18.104.22.168 Comments What kinds of organizations employ epidemiologists ? What kinds of organizations use the data that epidemiologists collect ? What is the accepted estimate of stuttering incidence in the USA ? Re: Epidemiological data From: Bobbie Lubker Date: 11/3/99 Time: 6:33:34 PM Remote Name: 22.214.171.124 Comments What kinds of organizations employ epidemiologists? Every state health department in the US employs epidemiologists. Many city and county health departments also employ their own epidemiologists, and all local health departments have access to state epid services. NIH, FDA and the Centers for Disease Control and Prevention have large cadres of these scientists. The CDC epid program monitors endemic and epidemic rates of certain reportable infectious diseases (rabies, rubella, measles, HIV,etc). CEC also monitors rates of congenital anomalies. Pharmaceutical companies have epidemiologists whose expertise lies in design of projects such as clinical trials for new treatments. All large hospitals and medical centers employ epidemiologists, and every hospital has access to epid consult. Epidemiologists in these settings monitor nosocomial infections (look it up!), utilization of ER facilities, birth and death rates, make-up of catchment areas and a host of population characteristics. Many industries employ epidemiologists to study absenteeism, employee health, insurance plans suitable for particular workforces, and controls for accident prevention. WHO, Pan-American Health Organization, various European , Asian and other health organizations around the world generate and utilize epid data for health planning and policy development. Epidemiologists are found wherever questions are asked about increased or decreased risk, measurement of risk (SLPs and As toss the words *at risk* around much too casually. At least four different measures of risk are used routinely in epid. See new ASHA Prevention Manual), documentation of prevention effects, and population distributions of health events. I am unusual in that my primary employment is in a school of education with a joint appointment in speech and hearing sciences in a medical school. I am director of the Center for Educational Management of Chronically Ill Children and Adolescents. My research is on the changing epidemiology of language-learning disorders in chronically ill children, administrative models and services (including speech-language-hearing services) in hospital schools, and educational transitions for children with language-learning disorders deriving from iatrogenesis (look it up!) - true incidence! What kinds of organizations use the data that epidemiologists collect? ASHA, for one. Herb Baum at ASHA has expertise (doctorate in public health sciences from Hopkins) in population research design, and ASHA now has an epidemiologist named Rob Mullen. And it*s about time. In the past ASHA undertook some research projects without having the epidemiological expertise required for such investigations. Survey research, which can be incredibly badly done by the naive and uninformed, is a major epid research method. The ASHA Omnibus survey follows epid principles. The Human Genome Project is an excellent example of an organization that utilizes science ranging from population trends (epid) to the molecular. The Red Cross, FEMA, March of Dimes, AARP, ACLD, ARC, all the disease-specific foundations, professional associations (AMA, APA, ANA, ADA) and scores of others use epid data that measure risk, survival rates, recovery rates, primary health conditions, secondary health conditions (e.g., communication disorders),treatment efficacy...just about anything about health that anybody can think of measuring...from birthweight and gestational age to the incidence ( yes, incidence) of deafness in Costa Rica. Much of what you read in the paper about health events is based on epid. For example, Three Mile Island outcomes, the Gulf War Syndrome, new medications, the HIV epidemic, responses to vaccines, influenza outbreaks in Hong Kong, resurgence of interest in thalidomide, eboli outbreaks, leukemia following the Chernobyl meltdown, changing rates of birth incidence of Down Syndrome, Alzheimer*s (age of onset, race-sex distributions)..and on and on...these are epid data. The geographic plotting of HIV occurrence in Africa follows the building of highways. Epid is a tool to inform policy and principles on which practice may be based. It is not usually intended to inform the treatment of a particular individual What is the accepted estimate of stuttering incidence in the USA? I have no idea. Well, actually I have an idea, but I want to make a point or two. Having an "accepted" estimate of stuttering incidence and an "accurate" estimate of stuttering incidence may be two totally different considerations. Go back and look at the article. As far as I know, no true incidence data have ever been generated. Again, as far as I know, no appropriate strategies for collecting incidence data have ever been employed. Mansson (1997) reported a proportion of about 5% for stuttering in a longitudinal study of three year olds...but longitudinal design does not necessarily mean that incidence data are obtained. Mansson and a team screened all the children in a contained population, but the important point is this: They reported stuttering after onset. They will have missed any children who started to stutter and stopped prior to the screening (NEW CASES!). This is not likely to be a large proportion, but from a theoretical perspective, they have not obtained incidence data. Yairi and Ambrose (1999) have begun to report data on remission rates in children identified very near the onset of stuttering, but these authors seem not to have reported population denominators that are absolutely essential for incidence rate calculation. Further, participants responding to *recruiters* may be different from those who do not choose to participate...and on and on. If (and it's a big "if"), the prevalence rate in adults is (for ease of calculation) 1%, and the recovery rate (for ease of calculation) is about 80%, simple arithmetic supports an incidence rate of about 5%....but none of these estimates has been calculated from pure epid models. Probably my most important point: Let me say also that it probably doesn't matter whether a national incidence rate is identified to the fourth decimal place. Such gross rates are not very useful information except to get a handle on the magnitude of the problem. What may matter more is that we come close enough with population-specific measures (e.g. males and females, laterality groups) so that statistically significant differences can be measured between clearly defined smaller populations. What else matters is that we are sophisticated enough to recognize the impact of methodological procedures on whatever rates we are trying to measure. Does all that make sense? It's clear to me! See also my comments to Melissa Bolling about normal functioning, randomness, sampling and probability theory below. Compliment to Author From: Fran Freeman Date: 10/4/99 Time: 12:35:37 PM Remote Name: 126.96.36.199 Comments Greatly enjoyed the article. I have printed it out so I can study it carefully for questions and comments. This p.m. I am assigning the article to my students who will also be reading Susan Felsenfeld's chapter on Epidemiology and genetics of stuttering. Good Work. Re: Compliment to Author From: Bobbie Lubker Date: 11/3/99 Time: 6:38:57 PM Remote Name: 188.8.131.52 Comments Thank you your enthusiastic comments. I hope the article's rather breezy, cheery and casual tone does not prohibit its being taken seriously as a forum for scientific method. I have not read the Falsenfeld chapter on genetics and the epidemiology of stuttering. Could you please send me the reference? I've been away from stuttering and into other aspects of epid for many years. You will want to look at the work of Falsenfeld and Plomen in the reference presented below. See what you think about their assertions about incidence data. What have you learned from my article? Falsenfeld, S. & Plomin, R. (1997). Epidemiological and offspring analyses of developmental speech disorders using data from the Colorado adoption project. Journal of Speech, Language and Hearing Research, 40, 778-791. I have written a letter to the ASHA Editorial Board about the spate of inaccurate epid concepts being accepted for publication in our most prestigious journals. Incidence studies From: Melisa Bolling (East Carolina University) Date: 10/6/99 Time: 7:56:53 AM Remote Name: 184.108.40.206 Comments Bobbie Lubker, Hello. I'm a first year graduate student at East Carolina University this year. I enjoyed reading your article "Who Stutters? When and Where as Clues to Why" and wanted to ask you a question. As an epidemiologist, you say that there is no incidence data for stuttering. I can understand why because it's difficult for me to even think of a way researchers could study incidence as you define it in your article. Perhaps one could perform a long-term study where they select a representative group of normally functioning children (it seems as though the group would have to be very large) at a prelingual stage and follow them throughout the years. Periodically, the subjects would be assessed for any type of stuttering behaviors. However, it seems you could choose 1000 children to participate, and at the end of your study, none of them were found to stutter - that would be discouraging! Do you have any ideas about how one could possibly come up with this incident data? Thank you for your time! Melisa Bolling Re: Incidence studies From: Bobbie Lubker Date: 11/3/99 Time: 6:42:47 PM Remote Name: 220.127.116.11 Comments Ms. Bolling, you have raised some very sophisticated epidemiological issues. Let's look at several of the issues in the order in which you have presented them. 1. Little semantics here: incidence "...as you define it in your article". I hope it's clear that this is not just my definition. It is an internationally accepted definition in public health. If SLPs and As want to "speak epidemiology"...I firmly believe that accurate use of the lexicon indicates basic understanding...we will use the vocabulary in ways that are understood by other professions. Right now we don't do that. I'm working on it. 2. "Perhaps one could perform a long-term study where they (sic) select a representative group of normally functioning children (it seems as though the group would have to be very large) at a prelingual stage and follow them throughout the years. Periodically the subjects would be assessed for any type of stuttering behaviors." You are exactly right. The only way to generate true incidence data is to start with a pre-lingual population free from stuttering and follow it over time. Those who develop fluency disorders are called "incident cases". Be careful of the study admission criterion of "normally functioning". Do you want to know about the incidence in children with Down Syndrome compared with children who have no known chromosomal anomalies? The outcome variable will be "stuttering" with severity strata defined. We will also control...not in subject selection and matching the way clinicians often do...but via analysis for race, sex, birthweight, cognitive development, and a lot of other good stuff. The importance of this research method is that we retain denominator data, the population in which the stuttering group "lives" and develops. Denominators are the heart beat of epid. Another article! Size of the group. This is an issue of probability and sampling theory. I offer the reference below. Incidence studies are cohort studies. Case-control studies are those most familiar to clinicians. Schlesselman (and others in epid and biostat) discuss some sampling strategies that I hope will become of interest to clinicians....such as use of multiple controls to increase informativeness. Schlesselman, J. J. (1974). Sample size requirements in cohort and case-control studies. American Journal of Epidemiology, 99, 6. Periodic assessment. Read Mansson (1997) and some of the new work published by Yairi and his colleagues in JSLHR. They toss and mis-toss epid concepts around rather too freely, but their emphasis on evaluations over time is right on. They do not report incidence data. 3. "However, it seems you could choose 1000 children to participate, and at the end of your study, none of them were found to stutter - that would be discouraging!" Go back to your own comment about having a "representative group". I suggest that you go to the ECU department of statistics and talk with somebody about probability and sampling theory. That's what your question is actually about. A couple of issues are hidden in your comment. You won't just "choose a 1000 children to participate". If, in your study, you employ accepted principles of probability to draw a sample (random sampling, systematic sampling, etc.), and if our estimates of incidence over the years are anywhere near accurate, it would be most unusual to draw a sample of prelingual children in whom no stuttering appears. That would not be a representative sample. If our 5% incidence estimates are in the ballpark, then we would expect 50 children in a probability sample to become dysfluent enough to fall into the stuttering category. If probability samplings shows subgroups in which the 5% incidence estimate does not hold true, then we are on to something. Also look at an oldie but a goodie: Slonim, M. J. (1960). Sampling. New York:Simon and Schuster Lots of more recent books about probability and sampling are out there. This remains my favorite for beginners. There may even be newer editions of this one. I hang on to my dog-eared copy. Now, several other complex epidemiological issues raise their tousled heads. It is not necessary and may not even be desirable to have "children" as the sampled unit. Read what Bruce Tomblin and his colleagues have written about designing a sampling frame comprised of schools as the sampling unit in studies of specific language disability. In your study, you might want to use day care centers as the sampled units in your probability sample! Another complex concern is that stuttering probably does not occur randomly in the population. If stuttering is, as Fran Freeman suggests a) more than one disorder (and epid distributions tend to indicate that it is more than one disorder!!) and further, b) genetically determined in some groups, then it for sure is not randomly distributed. We would expect family clusters in non-mobile societies and other distributions in mobile societies. The issues of incidence rates and prevalence rates, their association with risk factors, and meaningful risk calculations are subjects for another day. 4. "Do you have any ideas about how one could possibly come up with this (sic) incident (sic) data?" Yes, I have lots of ideas...see above...but not in a one-shot deal on the Internet! Is that too blunt? Such an approach is not fair to you as a learner. The late Dr. John Cassel ( He was to epid as Van Riper was to communication disorders.) used to say, "The less one knows about something, the greater the tendency to over-simplify; the more one knows about something, the harder it is to make it simple." Hie yourself over to the ECU Medical School. Charm them with your knowledge, interests and good questions. Push to enroll in (or at least sit in on) lectures that they are sure to have on epid for physicians. I warn you that such lectures are likely to be dull as dishwater, but you can make it interesting by applying the knowledge to your areas of clinical interest. Don't fall into the unfortunate pattern that is evolving in speech and hearing sciences. Lots of people are publishing inaccurate epid data generated from inappropriate research methods....and they don't seem to recognize that a theoretical base, a knowledge base and specific kinds of research design expertise are required. They don't know what their information gaps are. These are the same people who get all bent out of shape when other folks mess about in communication disorders without having what our profession has established as knowledge and skill foundations. 5. Will you be at NCSHLA in the spring? I'm a past president. Maybe we can "speak epid" with each other there. We can talk more about how to wangle your way into an epid course in the Medical School. geographical areas From: LaVonne Reed Date: 10/7/99 Time: 2:43:06 PM Remote Name: 18.104.22.168 Comments Thank you, I have a much clearer picture of what epidemiology is excatly, and a better understanding of the difference between incidence and prevalence. You mentioned there is data that indicates population clusters of people who stutter that exist in geographical regions. Are you aware of any regions in the United States that have a higher population of people who stutter? Re: geographical areas From: Bobbie Lubker Date: 11/3/99 Time: 6:46:15 PM Remote Name: 22.214.171.124 Comments Thank you for your comments. It is gratifying for readers to acknowledge having obtained new knowledge! Be cautioned, though, that what I elected to present for this article just scratches the surface of epidemiology. "You mentioned there is data that indicates population clusters of people who stutter that exist in geographical regions. Are you aware of any regions in the US that have a higher population of people who stutter?" The simple, simplistic answer to your question is, no, I don't know of regions in the US with increased prevalence of stuttering, but....I think appropriate questions have often not been posed about this. We have tip-toed very gingerly around some issues in stuttering research. Let me approach your question from a different perspective....not just regional differences but region as a proxy for some other population variables. I don't have it in front of me...it's the kind of information that doesn't get into speech and hearing reference lists....but a man named Brophy (and somebody whose name I can't remember in a journal I can find for you!) estimated some years back that the prevalence of stuttering among adults in western Africa is as high as 5%. I'm sure others have written on this too. Anecdotal data: A young Black woman exchange student from Liberia lived in my home for a while some years ago. She had, by any observational measure, moderate, sometimes severe stuttering. She is one of 16 children. Her mother and, if I remember correctly, 11 of her siblings stutter. Now, if incidence rates, recovery rates and prevalence rates are, in fact, different among the Black populations of western Africa from those in other parts of the world, could we form the hypothesis that regions settled by immigrants from western Africa would have rates of stuttering different from those in groups from other racial pools even in the same region? Or...another question might be about whether stuttering rates are different among west Africans who immigrated and those who stayed at home. Another approach to your question is whether there are likely to be clusters of people who stutter in communities that have good health services....including communication disorders services. They come for treatment, and they stay....for all kinds of reasons. Certainly we know this phenomenon with cancer, cystic fibrosis, and other major health conditions. Major medical centers and their specializations distort epidemiologic prevalence data. My bias as an epidemiologist about Wendell Johnson's work on stuttering among Native Americans several professional generations ago is that he was actually asking genetic questions, not cultural questions! Notice that I acknowledge my bias. Have I told you more than you care to know? Is it only in the stutterer's mouth? From: Jeff Knox Date: 10/15/99 Time: 12:18:53 PM Remote Name: 126.96.36.199 Comments Very interesting paper. I was trained at U of Iowa, so the diagnosgenic approach to stuttering has been of interest to me for several decades now. Ehud Yairi and I were students together with Dean Williams as our mentor. There must be something to the thought that perception is 90% of fact--you think you can't hit a golf ball and you may not be able to, etc. Also there must be something in the speech, especially the fluency characteristics of the speech of stutterers, which calls attention to listeners that this is different. I applaud everyone trying to do studies, so we can identify just what those characteristics are-- Interesting!! Re: Is it only in the stutterer's mouth? From: Bobbie Lubker Date: 11/3/99 Time: 6:49:07 PM Remote Name: 188.8.131.52 Comments Thanks so much for identifying yourself as an "old timer" who has been around for several decades. I'm delighted that the article seemed to resonate with you. I may be one of the few people out here in the world who met Wendell Johnson and Charles Van Riper and Bryng Bryngelson and Lee Travis and the second generation of Dean Williams and Hugh Morris, who is, of course, still around. I even met Ollie Backus and Jane Beasley who were doing child language therapy and calling it something else. Ehud Yairi and his colleagues are breaking out of the mold in their excellent work on recovery rates and the characteristics of those who recover and those who don't. They need a good epidemiology consultant because they are making some insupportable statements, and they apparently are not collecting denominator data, but they are pioneering. My quarrel is, in part, with the reviewers of manuscripts who pretend to expertise they don't have and accept some epid misinterpretations that should not find their way into print. I'll have to solve that another day. "There must be something to the thought that perception is 90% of fact--you think you can't hit a golf ball and you may not be able to, etc." Whose perception? According to the dx theory, it's other people's perceptions that cause the speaker to develop the problem. According to your golf ball example, it's one's own perceptions that cause the problem. Or is it one's own perceptions about others' perceptions that cause the problem? A major flaw in the dx theory is this causal conceptual leap: my perceptions can have such a powerful impact on your perceptions and subsequently on your behavior. The dx theory meets none of the epidemiological causal criteria (which is another article in itself!). It does not meet the temporal sequence criterion: cause always comes before effect. It seems to me that you are right on target, and you are getting at this principle in your comments about fluency characteristics that listeners respond to. These characteristics clearly, in my opinion, precede the so-called cause in the dx theory. Caretakers are concerned about some characteristics and not about others. I think the work of Yairi et al has marvelous potential to compare these behavioral events. I have forgotten (or repressed) a lot of what I used to know about the dx theory. The dx theory does not seem to consider what is known as "the dose/response criterion": How much "dose" of calling attention does it take to create stuttering (the response)? Does a little attention create mild stuttering? Does a lot of attention create severe stuttering? The dx theory, in my opinion, kept us from a generation of other kinds of research on stuttering. Wendell Johnson was a wonderful teacher and a charismatic man. I have one of the few copies of a film on stuttering made at Iowa in the '50s. Jim Lubker (my husband's distant cousin), a speech science Iowa graduate of your era, gave me the film. I had it repaired. Johnson was so convincing. Fransella and Beech wrote in the 1970s that stuttering theory in the US was more like profession of faith than science. The Who and When of Stuttering From: Terrence Lockett Date: 10/20/99 Time: 8:43:54 PM Remote Name: 184.108.40.206 Comments I was very informed by what I read in your article. Through reading many articles and books I can understand the link between stuttering and gender. My question is, does stuttering have a link to race and culture? Re: The Who and When of Stuttering From: Bobbie Lubker Date: 11/3/99 Time: 6:49:50 PM Remote Name: 220.127.116.11 Comments Read what I wrote to LaVonne Reed about geographic distributions. That starts to get at race as a variable. My informed epid opinion: I think there is absolutely no doubt that stuttering has different rates of occurrence and possibly in different racial groups. That's what we have tip-toed around about. If stuttering occurs more often in some races than in others, then offerings of early intervention and prevention must be informed by these racial differences. Do we know whether the male to female distributions hold up in racial groups other than white? I don't know that. Maybe somebody does. I acknowledge that my opinions about stuttering are very "biological/neurological". Again, what follows is an epid perspective: yes, I think we know that there are cultural differences, but we must use research design and statistical analyses (e.g., discriminate function analysis) that will permit us to control for race in asking questions about culture. If we study only white boys in university communities, then all we will know about is white boys in university communities. Bruce Tomblin and I have written a little bit about the epid selection biases resulting from studying only clinical populations. People who find their way to clinical services are quite different from the denominator population...and I believe race to be one of those differences. Thank you for your forthright, objective question. Who, When, Where From: Lynn K. Bender Date: 10/21/99 Time: 4:09:54 PM Remote Name: 18.104.22.168 Comments This is a very eye opening article. I do beleive that looking at stuttering in a different light may reveal things we never thought to consider. I would be interested in what a study would reveal when applied to epidemiology standards. Re: Who, When, Where From: Bobbie Lubker Date: 11/3/99 Time: 6:50:33 PM Remote Name: 22.214.171.124 Comments Right on, Lynn Bender! I think we absolutely must start to look at the shared characteristics of the sub-populations in which stuttering is and is not prevalent..in addition to the clinical characteristics of the stuttering. I have a couple of epid articles in mind that could be done relatively easily. Want to help with the lit reviews???? I moved into epid in part, as I wrote in the article, because of the '60s rubella epidemic, but my earliest research interests were in stuttering, and epid has given me a way back into that with new and different ways of thinking about populations, distributions and causality....and I hope, with some unique contributions to make. Closing comments to all who posted From: Bobbie Lubker Date: 11/3/99 Time: 6:53:11 PM Remote Name: 126.96.36.199 Comments Apologies for my delayed response to one and all who read about the epidemiology of stuttering in the cyberspace conference. I stopped all but the absolutely essential aspects of my life to work with contractors to repair a flooded house and to care for my elderly mother who has aphasia and who is in sudden and precipitous decline. I appreciate your interest in epidemiology. Judy Kuster, chief-honcho-in-charge of the Internet conference on stuttering, was kind enough to forward your comments to me so that I could respond to them in an expanded time frame. Your comments and questions confirm my suspicions that we really do need to use information on epidemiology and its interpretation to inform policy, practice, research design, training and decision making in speech, language and hearing sciences. I encourage each of you to find a good intro epid course. 'Good' being the operative word. They can be mind-numbingly tedious with little understanding of what novice learners need even to formulate questions and enter the discussion. Reading a book won't get it. Most epidemiologists have never even considered communication disorders from epid perspectives; they are surprised when I say that there are ninety thousand SLPs and As. Any way, your questions recharged my batteries.