Genetic Studies of Questionnaire Data from a Residential School for the Deaf

GENETIC STUDIES OF QUESTIONNAIRE DATA FROM A RESIDENTIAL SCHOOL FOR THE DEAF Frederick R. Bieber, Ph.D. viii f�edical College of Virginia Virginia Commom�ealth University, 1981. Major Professor: Walter E. Nance, M.D., Ph.D. A self-administered thirteen page Hearing Loss Questionnaire (HLQ) was designed in order to systematically collect medical and family his­ tory data on deaf children and their families. Data were collected from over 400 families with one or more children enrolled in September 1979 at the Maryland School for the Deaf (MSD). Almost 70% of the parents provided pedigree and family history information by completing the detailed HLQ. Computer analyses of the collected data allowed a thorough examination of almost 200 medical and family history variables, providing useful reference data on the MSD probands. Parental responses to a four-step rating scale of proband hearing ability were compared with actual audiometric data, allowing comparison �lith similar data from previous studies of hearing populations. Family history data on the non-respondents were available from school records, providing a unique opportunity to assess the potential response bias in question­ naire studies of genetic disease. Segregation analysis was performed on the informative sibships ascertained by incomplete truncate se­ lection. The pooled estimate of the ascertqinment probability, II, was 0.488, with no significant evidence of heterogeneity among the re­ spondents and non-respondents. The hypothesis of fully penetrant domi­ nant inheritance (H0:p=0.50) was accepted in the Deaf by Hearing matings. However, the maximum likelihood estimate of the segregation ratio (p=0.257) was consistent with reduced penetrance in these fami­ lies, as it also was in the Deaf by Deaf matings (p=0.31). There were no significant differences in the maximum likelihood estimates of£ or ix of the proportion of sporadic cases, �· between respondents and non­ respondents in the Hearing by Hearing matings. Among the non-consanguin­ eous Hearing by Hearing matings with no family history of hearing loss, the maximum likelihood estimate of x was 0.81. The removal of 46 sib­ ships with probands born during the 1964-65 rubella epidemic reduced x to 0.71, indicating the potential value of segregation analysis for moni� taring the secular trends in sporadic vs. genetic deafness. Among Hear­ ing by Hearing matings with a family history of early onset hearing loss, a recessive hypothesis wit. h no sporadic cases (H0:p=0.25, x=O.OO) fit the data well. However, the same hypothesis 1vas rejected among the Hearing by Hearing matings w.ith a family history of "presbycusis", where x=0.59. Thus, although a family history of early onset hearing loss appears to ·be a much more reliable index of a genetic etiology that does a family history of "presbycusis", the results of this study suggest that the latter may also be a positive risk factor. The HLQ data implied that both parents and doctors may underestimate the extent to which genetic factors contribute to childhood hearing loss, even in the presence of a· positive family history. Genetic factors were estimated to account for approximately 35% of the deafness in the MSD population. In the group with genetic deafness, the estimated proportions of recessive, dominant, and X-linked deafness were 57%, 39. %, and 5% respectively. Comparison of the estimates in the respondent vs. the non-respondent·groups revealed remarkable similarity betv;een the two groups, indiccti:ing that the use of the HLQ did not further confound existing biases. This study has demon­ strated the value and utility of using self-administered questionnaires· in genetic research. Indeed, the HLQ may serve as a usefu 1 prototype for future large scale population based studies of deafness in man.