Unit 2 - Incidence, Prevalence, & Variability - Students PDF

UNIT 2: INCIDENCE, PREVALENCE & VARIABILITY CSDS 115 – FALL 2024 DEBBIE MOORE, M.A.,CCC-SLP  2 OBJECTIVES  Describe the meanings of the terms “prevalence” and “incidence”  Understand the incidence...

UNIT 2: INCIDENCE, PREVALENCE & VARIABILITY CSDS 115 – FALL 2024 DEBBIE MOORE, M.A.,CCC-SLP  2 OBJECTIVES  Describe the meanings of the terms “prevalence” and “incidence”  Understand the incidence and prevalence studies of stuttering  Understand the factors that are important in the incidence and prevalence of stuttering  Understand the variability and predictability in stuttering  Define and understand anticipation, consistency, and adaptation  Define and understand the various speaking conditions that may reduce stuttering behaviors  3 INCIDENCE  Incidence is the rate of occurrence of a given disorder or disease in a specified group of people  Studied by the longitudinal method  Is a predictive statement  Incidence studies are more expensive than prevalence studies  An incidence study starts with a healthy or normal group; repeatedly observes the same individuals over a period of time and counts the number of individuals who begin to show the disease or the disorder  4 PREVALENCE  Prevalence is the number of individuals who currently have a disorder or disease  Involves a head count  Uses a cross-sectional method of study  Is not a predictive statement; it is a statement of current number of persons with the disorder  Studies are less expensive than incidence studies  A prevalence study starts with clinical records of individuals who already exhibit the disorder. It collects information from various sources and adds numbers  5 INCIDENCE VS. PREVALENCE OF STUTTERING  There are fewer studies of incidence of stuttering  Most available are prevalence studies  Most studies are rough estimates  6 PREVALENCE STUDIES  PIONEER REPORTS (Early investigation around 100 years ago)  Four large studies with a total of 660,000 participants revealed very similar results:  Lindberg (1900) Danish -.90%  Von Sarbo (1902) Hungarian – 1.02%  Hartwell (1895) American, Boston -.77%  Conradi (1904) American -.77%  These results indicate a group mean of about.89%  7 PREVALENCE CHART FROM YAIRI & SEERY (2015) The prevalence of stuttering are consistent with studies done later than the Pioneer Click icon to add picture studies Studies on prevalence performed on just preschool age children yield higher prevalence rates  8 INCIDENCE STUDIES  Incidence is less likely to be accurate due to the difficulty of attaining valid longitudinal data  Andrews & Harris (1964) studies 1,142 babies in England and tracked them from birth to their 16th birthday  43 children exhibited stuttering, amounting to 4.9% more than any other study  This study has influenced the generally accepted notion that the lifetime incidence of stuttering is approximately 5%  9 INCIDENCE STUDIES Cont.  Four of 6 recent incidence studies indicate a trend up from 5% to a central figure of 8% or higher  Important to emphasize data obtained in early childhood are more valid than data obtained at any other age  Many researchers (Yairi & Ambrose (2013), Bloodstein & Ratner (2008)) believe that lifetime incidence could be at least 10%  10 ONSET OF STUTTERING  Vast majority of developmental stuttering cases begin in early childhood  Stuttering generally appears after the skills of normal fluency have already been demonstrated  Widely accepted that the vast majority of stuttering begins from ages 2-4  In one study of 179 stuttering children, only 5 had onset later than the age of 4 (Mansson, 2000) FACTORS TO CONSIDER IN INCIDENCE AND PREVALENCE FOR STUTTERING  12 ONSET OF STUTTERING Cont.  The following factors are important in the prevalence and incidence of stuttering:  Spontaneous Recovery (Natural Recovery)  Gender Ratio  Genetic Perspectives: Familial Prevalence  Genetic Perspectives: Concordance Rate in Twins  Genetic Perspectives: Adoption  Genetic Perspectives: Genes  Prevalence in Other Selected Populations  Ethnocultural Variables  13 SPONTANEOUS RECOVERY (NATURAL RECOVERY)  Some children or adolescents recover from stuttering without professional help  Spontaneous recovery data apply to group and not to individual clients  It is not possible to predict whether a given child will or will not recover spontaneously  14 GENDER RATIO  More common in males than in females  The most frequently cited ratio is 3:1 (male: female) for children in earlier elementary grades  The ratio is larger in higher grades (perhaps 4:1)  15 GENETIC PERSPECTIVES: FAMILIAL PREVALENCE  Familial prevalence is the frequency with which a given condition occurs within a family group  Familial incidence of 30%-60% compared with 10% for families of normally fluent controls (Yairi, Ambrose, & Cox, 1996)  More than 3 to 4 times higher than that in the general public  Male relatives are more likely to stutter than female relatives, 39% to 15% (Kay, 1964)  Some evidence suggests that compared to families that have a male stutterer, familial prevalence is higher in families that have a female stutterer  Familial incidence may be explained on the basis of genetic or environmental factors  16 GENETIC PERSPECTIVES: CONCORDANCE RATE IN TWINS  Stuttering occurs most often in both identical twin pairs compared to both fraternal, same sex twin pairs  Higher concordance rate in identical twins than fraternal twins  If only one member of a twin pair has a condition and the other does not, then the pair is discordant  Supports the hypothesis that stuttering is inherited  17 GENETIC PERSPECTIVES: ADOPTION  Studies with this population are rare  Adoption studies show there may be stronger evidence for the influence of environment on stuttering  18 GENETIC PERSPECTIVE: GENES  Genetic linkage studies  DNA is compared among family members  Numerous studies have been published  Genome-Wide Association Study  More interested in the genes, not the chromosomes  Identified 10 “candidate genes”  Subdivided into neural development, neural function, and behavior  19 GENETIC PERSPECTIVES: GENOTYPING There is strong evidence for Click icon to add picture major genetic components to stuttering Studies analyzing DNA materials to locate candidate genes have been promising  20 PREVALENCE IN OTHER SELECTED POPULATIONS  A somewhat higher prevalence of stuttering than for the general population has been reported for:  Individuals with cognitive impairment  Early studies 14-17% (Gottsleben, 1995; Schlanger & Gottsleben, 1957)  Later studies 2.5% to 7 % (Chapman & Cooper, 1973; Schaeffer & Shearer, 1968  Down Syndrome in particular – 15% (Schubert, 1966) up to 53.2% (Preus, 1973)  Suresh et al (2006) found the strongest indications for genes underlying stuttering on chromosome 21  21 PREVALENCE IN OTHER SELECTED POPULATIONS Cont.  A lower prevalence of stuttering has been reported in deaf and hard of hearing individuals  Stuttering in deaf persons with oral skills has been documented but with very low prevalence rates (.05% Backus, 1938; Harms & Malone, 1939)  A lower prevalence of stuttering has been reported in the cleft palate population (Dalston 1987,.2%)  22 ETHNOCULTURAL VARIABLES  Some experts, Johnson, have claimed that stuttering is a culturally determined disorder  This is in line with the diagnsogenic theory of stuttering  Johnson believed that societies and cultures that place a heavy emphasis on verbal skills have a higher prevalence of stuttering  Johnson further believed that Native Americans do not stutter; Snidecore, 1947 claimed Native Americans didn’t even have a word for stuttering  Johnson’s theory has been contradicted by data – stuttering is found in almost all societies and ethnocultural groups  The prevalence rates may be somewhat different in different ethnocultural groups  CONGENITAL AND EARLY 23 CHILDHOOD FACTORS IN STUTTERING  West, Nelson, and Berry (1939)  Alm & Risberg (2007)  100/204 participants reported no family  23/32 (72%) reported a family history of history of stuttering stuttering  85/100 participants reported congenital or  17/32 (53%) sustained neurological early childhood factors lesions prior to the onset of stuttering  Conclusion was congenital or early childhood  7/9 (78%) with no family history of factors may be a predisposition for stuttering stuttering, reported pre-onset  Poulos & Webster (1991) neurological lesions  57/169 participants reported no family history  Supports the hypothesis that 2 different of stuttering predispositions may contribute to  37% reported congenital or early childhood stuttering factors  Genetic inheritance  Conclusion was congenital or early childhood factors may be a predisposition for stuttering  Brain injury  24 BRAIN FUNCTION DIFFERENCES  Cerebral dominance for speech  Cerebral Blood Flow Studies  Greater right-hemisphere activity  Greater activity in the right frontal  Left-hemisphere structures may have operculum deficits/delays in development  Less left hemispheric dominance  Electroencephalographic Studies  Positron Emission Tomography (EEG)  Studies (PET) Results of studies varies  Right hemisphere areas are not  More likely to have a right- designed for rapid speech hemisphere dominance for speech and language (right frontal  Unable to function well enough to operculum) produce fluent speech  25 BRAIN STRUCTURE DIFFERENCES IN PEOPLE WHO STUTTER  Numerous studies have examined brain anatomy in adults who stutter  Shape  Size  Density of speech and language areas  Suggests that sensory, planning and motor areas of the left hemisphere developed differently  26 WHOLE BRAIN INTRINSIC NETWORK CONNECTIVITY  Studies the entire cortex of the brain  Stuttering was associated with attention, motor performance, perception, and emotions  May explain why stuttering co-occurs with other disorders  27 CHANGES IN BRAIN ACTIVITY AFTER TREATMENT  Left hemisphere was revitalized  Right hemisphere became more normally activated  VARIABILITY AND PREDICTABILITY IN STUTTERING  29 VARIABLES THAT AFFECT STUTTERING FREQUENCY  The frequency or the severity of stuttering varies tremendously  May be more disfluent when they speak under pressure  Each speaker may perceive communicative pressure in different ways  30 WHEN ARE PEOPLE WHO STUTTER MORE DYSFLUENT?  Speaking to strangers  Speaking to authority figures  Ordering in restaurants  Asking for directions  Speaking on the telephone  Using certain words  Formulating their own speech  Speaking in a hurry  Speaking to groups  31 OTHER VARIABLES  Stuttering variability  Situations  Reading vs speaking  Strangers vs familiar people  32 ADDITIONAL FLUENCY INDUCING CONDITIONS  Talking to people regarded as inferior  Inconsequential remarks  Speaking with a change of pitch  Speaking to infants  Speaking from memory  Speaking to animals  Speaking with more familiar  Speaking when relaxed individuals  Emotionally distracting/intense  Whispering stimuli  Swearing  33 ANTICIPATION, CONSISTENCY, & ADAPTATION  Several studies showed that stuttering was not only a neurophysiological disorder, but also a learned behavior  Anticipation is predicting the words or sounds on which the person will stutter  Consistency is stuttering on the same word when reading the same passage a few times  Adaptation is when stuttering decreases with repeated trials  Opened the door to new treatment options  34 LANGUGE FACTORS  Several studies have been conducted to determine if there is a correlation between stuttering and language  Results have shown a strong relationship between stuttering and language  35 SPEAKING CONDITIONS THAT REDUCE STUTTERING  Delayed Auditory Feedback/Prolonged Speech  Masking  Adaptation  Rhythmic Stimulation  Altered Prosody  Reduced Speech Rate  Choral Reading and Shadowing  36 DELAYED AUDITORY FEEDBACK (DAF)  Longest history as a treatment procedure  Method to delay a speaker’s feedback through headphones with mechanically varied delay  Speech Easy is a variation of DAF, also includes Frequency Altered Feedback (FAF)  Lee, 1950, first reported the effect of DAF  Delay of.2 seconds is effective  In stuttering speakers, disfluencies decrease and syllables are prolonged 37  38 MASKING  First reported in 1955 (Shane in U.S.)  Headphone induced white noise in varying intensity and frequency  Usually temporary  Explanation of effect included inherent auditory feedback deficit  The following effects are noted:  Increased vocal intensity  Vowel durations are longer  Stuttering frequency decreases  39 ADAPTATION  First researched by Johnson and Knott (1937)  Progressive reduction (up to a point) in the frequency of stuttering upon repeated oral reading of a printed passage  Adaptation is due to:  Anxiety deconfirmation  Fear reduction caused by stuttering itself  Rehearsal of the motor sequence and motor learning  A gradient of stimulus control, stuttering disappears on less strongly conditioned stimuli  Involves process within the basal ganglia  40 RYHTHMIC STIMULATION  Words and syllable are timed to a rhythmic stimulus (tapping, metronome)  Only method where speeding up doesn’t induce more disfluencies  Effect is temporary  Rhythm and syllabification are two of the most powerful factors that induce fluency  41 ALTERED PROSODY  Any speech pattern that the person is not used to can reduce stuttering frequency  These could include:  Singing  Slowing  Speaking in a dialect  Talking to an animal  Possibly related to the sensory-motor and cognitive demands of self- monitoring for these tasks, not necessarily the task itself that is responsible for fluency  42 REDUCED SPEECH RATE AND SHADOWING AND CHORAL READING  Creates a novel mode of speech that reduces stuttering frequency  Shadowing and Choral Reading is the same principle  Shadowing – the clinician reads and the client is 1-2 words behind  Choral Reading – Reading in unison  Effects are secondary to the removal of the discriminative stimuli for stuttering  43 DISCRIMINATIVE STIMULUS CONTROL  Creates different responses by correlating different consequences with distinctive cues  Which behaviors will be reinforced or punished  Is stuttering partially under some discriminative stimulus control?  Consider variable rates of stuttering under different circumstances (i.e. improved fluency with clinician)  Carry-over of fluency using a discriminative stimulus (i.e. Sticker)