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Sibship Size (sibship + size)
Selected AbstractsSibship analysis of associations between SNP haplotypes and a continuous trait with application to mammographic densityGENETIC EPIDEMIOLOGY, Issue 4 2010J. Stone Abstract Haplotype-based association studies have been proposed as a powerful comprehensive approach to identify causal genetic variation underlying complex diseases. Data comparisons within families offer the additional advantage of dealing naturally with complex sources of noise, confounding and population stratification. Two problems encountered when investigating associations between haplotypes and a continuous trait using data from sibships are (i) the need to define within-sibship comparisons for sibships of size greater than two and (ii) the difficulty of resolving the joint distribution of haplotype pairs within sibships in the absence of parental genotypes. We therefore propose first a method of orthogonal transformation of both outcomes and exposures that allow the decomposition of between- and within-sibship regression effects when sibship size is greater than two. We conducted a simulation study, which confirmed analysis using all members of a sibship is statistically more powerful than methods based on cross-sectional analysis or using subsets of sib-pairs. Second, we propose a simple permutation approach to avoid errors of inference due to the within-sibship correlation of any errors in haplotype assignment. These methods were applied to investigate the association between mammographic density (MD), a continuously distributed and heritable risk factor for breast cancer, and single nucleotide polymorphisms (SNPs) and haplotypes from the VDR gene using data from a study of 430 twins and sisters. We found evidence of association between MD and a 4-SNP VDR haplotype. In conclusion, our proposed method retains the benefits of the between- and within-pair analysis for pairs of siblings and can be implemented in standard software. Genet. Epidemiol. 34: 309,318, 2010. © 2009 Wiley-Liss, Inc. [source] Seroprevalence of Helicobacter pylori Infection Among Schoolchildren and Teachers in TaiwanHELICOBACTER, Issue 3 2007Ding-Bang Lin Abstract Background:,Helicobacter pylori are associated with chronic antral gastritis that is related to duodenal ulcer, gastric ulcer, and probably gastric adenocarcinoma. Infection of H. pylori during childhood is considered an important risk factor for gastric carcinoma in adult life. Materials and Methods:, To examine the epidemiologic characteristics of H. pylori infection among schoolchildren in central Taiwan, a community-based survey was carried out using stratified sampling in 10 elementary schools and three junior high schools including students and theirs teachers. Serum specimens of 1950 healthy schoolchildren (aged 9,15 years old) and 253 teachers who were randomly sampled were screened for the H. pylori antibodies by enzyme-linked immunosorbent assay. Statistical analysis was performed by using the spss for Windows statistical software system. Results:, A total of 332 subjects were H. pylori antibodies positive, giving an overall prevalence of 15.1%. The age-specific seropositive rates were 11.0% in 9,12 years age group, 12.3% in 13,15 years age group, and 45.1% in the teacher group. The older the age, the higher the seroprevalence (OR = 11.53; 95% CI = 6.73,19.74; p < .001 for children vs. teachers). There was no difference in the seroprevalence of H. pylori infection by gender, ethnicity, geographical area, socioeconomic level, parental education, sibship size, family members, and source of drinking water. Conclusion:, The teachers had a much higher prevalence of H. pylori antibodies. The finding suggests that these teachers (adults) might be infected in their early childhood and implies that the poor environmental and hygienic conditions might be responsible for it. It seemed that poor water supply system, sewage disposal, and other environmental hygiene in adult might play some roles in H. pylori infection in Taiwan (before early 1980s). [source] Seroepidemiology of hepatitis A, B, C, and E viruses infection among preschool children in TaiwanJOURNAL OF MEDICAL VIROLOGY, Issue 1 2006Jye-Bin Lin Abstract Taiwan was a hyperendemic area for hepatitis A and B viruses (HAV and HBV) infection before late 1980s. To study the seroprevalence of hepatitis A, B, C, and E viruses (HCV and HEV) infection among preschool children in Taiwan, a community-based survey was carried out in 54 kindergartens in 10 urban areas, 10 rural areas, and 2 aboriginal areas randomly selected through stratified sampling. Serum specimens of 2,538 preschool children were screened for the hepatitis A, C, and E antibodies by a commercially available enzyme immunoassay and for HBV markers by radioimmunoassay methods. The multivariate-adjusted odd ratios (OR) with their 95% confidence intervals (CI) were estimated through the multiple logistic regression analysis. Females had a statistically significantly higher HAV seroprevalence than males. The seroprevalence of HCV infection increased significantly with age. The larger the sibship size, the higher the seroprevalence of HBV infection. Aboriginal children had a significantly higher seroprevalence of HBV and HEV infection and lower seroprevalence of HCV infection than non-aboriginal children. A significantly higher seroprevalence of HBV infection was found in rural children than urban children. There was no significant association between serostatus of HAV and HEV infection and between serostatus of HBV and HCV infection among preschool children in Taiwan. The poor environmental and hygienic conditions in the aboriginal areas might play a role in infection with HBV and HEV. J. Med. Virol. 78:18,23, 2006. © 2005 Wiley-Liss, inc. [source] Increasing prevalence of allergic rhinitis but not asthma among children in Hong Kong from 1995 to 2001 (Phase 3 International Study of Asthma and Allergies in Childhood)PEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 1 2004So-Lun Lee There is a worldwide belief that the prevalence of asthma and other allergic diseases is increasing but the measures used in many studies are susceptible to systematic errors. We examined the trend of asthma, allergic rhinitis and eczema prevalence in school children aged 6,7 years in Hong Kong from 1995 to 2001 using standardized ISAAC methodology. There were 4448 and 3618 children participating in 2001 and 1995, respectively. The prevalence of life-time rhinitis (42.4% vs. 38.9%, p < 0.01), current rhinitis (37.4% vs. 35.1%, p < 0.03), current rhinoconjunctivitis (17.2 vs. 13.6%, p < 0.01) and life-time eczema (30.7% vs. 28.1%, p = 0.01) increased significantly. There was no significant change in prevalence of life-time asthma, life-time wheeze and current wheeze albeit a significant increase in severe asthma symptoms. We investigated a number of potential risk factors including sex, family history of atopy, sibship size, birth weight, respiratory tract infections, pet ownership and exposure to tobacco smoke. However, the increases in prevalence of rhinitis and eczema could not be entirely explained by the change of prevalence of these risk factors. The odds ratio OR for the study period remained significantly associated with current rhinitis (OR 1.31, 95% confidence intervals CI 1.17,1.46), current rhinoconjunctivitis (OR 1.63, 95% CI 1.41,1.87) and life-time eczema (OR 1.30, 95% CI 1.16,1.45) after adjustment for these confounding variables using logistic regression model. Further study is warranted to elucidate the factors contributing to the observable change in the prevalence of rhinitis in our population. [source] Birth order and sibship size as independent risk factors for asthma, allergy, and eczemaPEDIATRIC ALLERGY AND IMMUNOLOGY, Issue 6 2003Roos M. D. Bernsen This study was carried out to disentangle the independent relations of birth order and sibship size with the presence of asthma, allergy and eczema. In a retrospective study, 700 families in the Netherlands were selected with index children born in 1988,90. Data were extracted from reports of health examinations at the age of 6 years of these children and their siblings. Birth order, and not sibship size, appeared to be a strong risk factor for allergy (excluding eczema). Children with higher birth order had a lower risk of allergy compared with first-borns (adjusted odds ratios: 0.43, 0.26 and 0.05 for second-, third- and fourth- or higher borns, respectively; p < 0.0001). Allergy including eczema also had a significant relation with birth order (p = 0.01). For asthma there appeared no clear relation with birth order. For asthma a non-significant relationship with sibship size (adjusted for birth order) was found (p = 0.06): first-born children in small sibships were more at risk than those in larger sibships. For allergy and eczema no such trend was observed. In conclusion, birth order is inversely related to the risk of allergy, independent of the size of the sibship. [source] | |||||||||||||