The Studies Of Epidemiological Characteristics And Impact Factors Of The Commone Genes In Patients With Sensorineural Hearing Loss In China

Hearing loss is the most common sensory impairment. Genetic factors are attributed to over 50% of all etiological factors. Conducting genetic epidemiological studies of deafness genes will be valuable to revealing epidemiological characteristics of deafness genes, and providing important data for prophylaxis, counseling, early diagnosis, early intervention and treatment. But reviewing epidemiological literatures about deafness genes in the past 10 years, we found that there were large differences and some inconsistencies data from many studies. In order to reveal the epidemiological characteristics of deafness genes in Chinese populations and find some factors leading differences, we used group studies and comparative studies to reveal the mutation characteristics of mtDNA A1555G, GJB2 and SLC26A4, and reveal some impact factors of mutation frequencies in the three genes. Based on these impact factors, we suggested it was very necessary to regulate the sample inclusion criteria according to individual characteristics of every gene in order to make these criteria fit the standard of epidemiological study. This study is divided into two parts:Part one:The Situation Analysis of Epidemiological Studies of mitochondrial DNA 12SrRNAA1555G, GJB2 and SLC26A4 Mutations.In part one, we firstly reviewed some epidemiological data of the three common deafness genes in past ten years, and indicated the large differences and contradictions existing between these data were one of main problems in present epidemiological studies. In the first chapter of Part one, we collected all published epidemiological literatures about Chinese mtDNA A1555G mutation from 1996 to March,2008. By literature review and statistical analysis, we believed some deficiencies, such as insufficiency of samples, age bias and area bias, existed in epidemiological researches about mtDNA A1555G mutation in China. We believed that the number of samples was a very important factor that influenced the accuracy of epidemiological data in the past studies. So in the second chapter, we determined the number of samples by using the formula for sample size estimates, enrolled 485 patients with NSHL in Shandong Province and screened mutations of the three common deafness genes in these patient. Of 485 patients, 180 patients (37.11%) had two mutated alleles (homozygote and compound heterozygote) of GJB2 (24.12%) and SLC26A4 (7.42%) and mtDNA A1555G (5.57%). We supposed that about 24.5 thousand deaf-mute patients who were caused by the three sensitive deafness genes mutation in Shandong province.Part two:Group and Comparative studies of Epidemiological data of mtDNA A1555G, GJB2 and SLC26A4 mutationsIn the Part two study, we divided research samples into different subgroups according to their sources and characteristics, and then we compared the mutation frequencies of the three deafness genes between different subgroups in order to find some factors that influenced the accuracy of epidemiological data of the three deafness genes mutation frequencies. In Chapter one, we found mtDNA A1555G mutation frequency was influenced by the proportionalities of familial and sporadic patients, AAID and non-AAID patients in research samples. The proportionality of SES patients and outpatients in sporadic samples was also important impact factor. In Chapter two, we found GJB2 mutation frequency was influenced by the proportionality of prelingual and postlingual patients among samples. The proportionality of SES patients and outpatient in sporadic samples was also impact factor. In Chapter three, compared with GJB2 and mtDNA A1555G, the mutation frequency of SLC26A4 were influenced by more factors. The proportionality of familial and sporadic patients, prelingual and postlingual patients, SES and outpatients, EVAS and non-EVAS patients all influenced the accuracy of SLC26A4 mutation frequency.We suggested that Ethnic background, samples'sources and characteristics including familial or sporadic patients, hospital or SES patients, prelingual or postlingual patients, EVAS and non-EVAS patients, AAID or non-AAID patients were all important impact factors in epidemiological studies. But the effects of these factors were different or converse for different gene. So we must regulate the correct and reasonable sample inclusion criteria according to different genes' characteristics in order to effectively avoid significant differences among data of the epidemiological studies and ensure the accuracy and stability of research results.