An analysis of consanguineous marriage in the Muslim population of India at regional and state levels

Consanguineous Marriages and the Perception of Wife-Beating Justification in Pakistan: An Application of Fairlie Decomposition Analysis

Pakistan has a significant occurrence of both consanguineous marriages and intimate partner violence (IPV), which may be interlinked. The practice of consanguineous marriages could potentially influence women to rationalize and accept instances of IPV. Such attitudes perpetuate a culture of violence against women, creating difficulties for victims to reject or escape from it. Pakistan has high prevalence rate of consanguineous marriages and IPV. However, no research has been done to explain the difference in acceptance of IPV between women in consanguineous and non-consanguineous marriages. This study used Pakistan Demographic and Health Survey data and applied association tests, logistic regression, and the Fairlie decomposition analysis. The Fairlie decomposition helps us identify the relative contribution of different socioeconomic factors in the inequalities in IPV between the two types of marriages. Five dimensions of wife-beating justification are used as outcome variables. Age, education, and empowerment of women, husband education, woman witness parental violence, region, place of residence, and household wealth status are used as independent variables. The logistic regression results indicated that women in consanguineous marriages of younger age and who witnessed parental violence are more likely to justify wife-beating than those who belong to wealthy households and enjoy more empowerment. Compared to the Punjab province, women residing in Sindh and Baluchistan are less likely and in the Khyber Pakhtunkhwa province are more likely to justify wife-beating. The Fairlie decomposition analysis shows that household wealth status, woman education, and empowerment are the main contributors in explaining the gap between the wife-beating justification of the two groups. The IPV gap can be reduced up to 77% if the distribution of women in different wealth quantiles of the consanguineous marriage group is identical to the non-consanguineous marriage group. Furthermore, woman education level is the second highest contributor. Consanguineous marriages are a prevalent cultural practice in Pakistan and are associated with several negative health and social outcomes. Addressing this issue requires a sustained and comprehensive effort by the government, civil society, and international partners, with a particular focus on women from poor households with less education.

Effects of caste, birth season, and family income on digit ratios

OBJECTIVES

The contributions of latitude and ethnicity in the determination of cross-society differences in digit ratios are unclear. In India, different castes (endogamous groups) have been living in the same areas (villages or towns) for the last 1500 years and, therefore, these groups may have different gene pools without a latitude-related difference component. Thus, in the present study, we studied the effect of caste on digit ratios. We also studied the effects of sex, birth season, and family income on digit ratios.

METHODS

We selected a sample of 301 college students (age: M = 19.9 years, SD = 2.63) in Muzaffarnagar city of western Uttar Pradesh, India, and asked participants for information regarding their birth month, religion, caste, and monthly family income. We measured participants' dorsal and palmar digit lengths (of all fingers, except the thumb, in both hands) using vernier calipers of 0.01 mm accuracy.

RESULTS

Other backward castes (intermediate castes) had longer digit lengths than general castes (upper castes), scheduled castes (lower castes), and Muslims. However, there was no difference in digit ratios of caste groups (scheduled castes vs. other backward castes vs. general castes vs. Muslims) or specific castes (Chamar-Jatav vs. Jat vs. Pandit-Tyagi). Winter-born women had lower left dorsal 2D:4D and 3D:4D ratios than summer-born women. Family income was related to higher dorsal 2D:4D and 3D:4D ratios among women. Moreover, in dorsal digit ratios, sex difference (men < women) occurred in digit ratios constituting digit 5, whereas, in palmar digit ratios, sex difference occurred in digit ratios constituting digit 2.

CONCLUSIONS

The present study suggests that endogamy-led genetic difference in ethnic/caste groups is not a determinant, whereas birth season (i.e., the exposure to sunlight) and family income might be determinants of digit ratios. In addition, compared to palmar digit ratios, dorsal digit ratios are better markers of sexual dimorphism.

The epidemiology of apnoea of prematurity

WHAT IS KNOWN AND OBJECTIVE

Many premature infants less than 37 weeks gestational age (GA), and almost all infants less than 28 weeks GA, will experience apnoea of prematurity (AOP)-a cessation of respiration for 20 or more seconds (or less than 20 s if accompanied by other signs). Because the treatment options for AOP are so limited, we explore its epidemiology, with the ultimate hope of learning how to decrease its incidence.

COMMENT

Although AOP usually resolves with maturation of the respiratory system, many short- and long-term negative effects are correlated statistically with AOP (although direct causality has not been established). The primary risk factor for AOP is preterm birth, but delivery technique, genetics, socioeconomic status, racial disparities and other influences are suspected to be involved. Anaemia, asthma and gastric reflux have also been associated with preterm birth, but the relationship with AOP is unclear. The postulated associations and the strength of the evidence are briefly reviewed and discussed.

WHAT IS NEW AND CONCLUSION

Attempts to elucidate the epidemiology of apnoea of prematurity have been challenging. Studies of AOP are hampered in part by challenges in monitoring the condition, the interplay of multiple comorbidities in preterm neonates and lack of expert consensus definitions. However, since the primary risk factor is preterm birth, efforts to decrease the prevalence of preterm birth would have a positive secondary effect on the prevalence of AOP. Until then, better pharmacotherapeutic options are needed.

Consanguineous Marriages in India: Prevalence and Determinants

Consanguineous marriage is the legal union of male and female of a common ancestor related by blood. The most common prevailing form of consanguineous marriages is between first cousins. Middle East Asian countries and southern states in India show high prevalence. A comparative analysis between the two rounds of National Family Health Survey 1 and 4 have shown a declining trend for the practice of consanguineous marriages. The highest percentage of consanguineous marriages is seen among the first cousins from both father’s and mother’s side, most commonly practice in the southern states of Andhra Pradesh, Telangana, Tamil Nadu, and Karnataka except Kerala. Importantly, the practice of consanguineous marriage is higher among the Muslims of North India and Hindus of Southern India, among the Other Backward Classes and the less educated population of the middle and richer wealth index. A significant relationship can be noticed among consanguineous marriages and socio-economic variables.

Prevalence and determinants of consanguineous marriage and its types in India: evidence from the National Family Health Survey, 2015-2016

The aim of the present study was to estimate the prevalence and examine the determinants of consanguineous marriage types in India. Data for 456,646 ever-married women aged 15-49 years were analysed from the National Family Health Survey (NFHS)-4 conducted in 2015-16. The overall prevalence of consanguineous marriage was 9.9%; the South region (23%) and North-East region (3.1%) showed the highest and lowest prevalences, respectively. Muslims had a higher prevalence (15%) than Hindus (9%). The prevalence of first cousin marriage (8.7%) was more than that of second cousin (0.7%) and of uncle-niece marriages (0.6%). Women living in urban areas and in nuclear families, having a higher level of education and belonging to affluent families were less likely to marry their cousins (p < 0.01). Women living in the South region of the country were more likely to marry their cousins, as well as uncles (p < 0.001). Close scrutiny of the trends in the results (odds ratios) revealed no clear relationship between socioeconomic condition and consanguineous marriage. The study results suggest that religion and north-south regional dichotomy in culture largely determine consanguineous marriage rather than socioeconomic condition in India.

Novel OTOF pathogenic variant segregating with non-syndromic hearing loss in a consanguineous family from tribal Rajouri in Jammu and Kashmir

BACKGROUND

Hereditary hearing loss is characterized by a very high genetic heterogeneity. The OTOF (Locus: DFNB9), encoding otoferlin, is reported to be one of the major causes of non-syndromic hearing loss, and is also reported to be the most common cause of non-syndromic recessive auditory neuropathy spectrum disorder.

METHODS

In this study, whole exome sequencing was employed for detection of novel pathogenic variant that segregates with autosomal recessive nonsyndromic hearing loss in a tribal family from Rajouri, Jammu and Kashmir. Proband was a 9-year-old male born to first-cousin parents and presented with sensorineural hearing loss since birth. Family resides in an area with high consanguinity and lack of basic health care facilities including genetic counselling services.

RESULTS

We report a novel OTOF pathogenic variant NM_194248.2:c.4249_4250insG (p.Ser1417CysfsTer4) co-segregating with hearing loss in this family and not present in any public databases.

CONCLUSIONS

Our findings not only extend the geographical and mutational spectrum of autosomal recessive nonsyndromic hearing loss but also support the need for introducing genetic counselling services to rural and tribal areas in India with high consanguinity.

A Family Study of Consanguinity in Children with Intellectual Disabilities in Barwani, India

Background:

Intellectual disability (ID) can be inherited in families through consanguineous marriage. The ID in an individual can be associated with the ID, epilepsy, and mental illness in their parents. Such connections can be seen more closely among consanguineous marriages in tribal and nontribal population in India.

Objective:

This study shows a few common patterns of the consanguineous relationship in the parents of children with ID in India.

Materials and Methods:

This is a case series research design. Extreme or deviant case sampling was applied. Data were collected in homes, camps, and clinical settings in the Barwani district of Madhya Pradesh, India. The patterns of consanguineous marriages and the relationship between children with ID and their relatives with ID, epilepsy, and mental illness were analyzed and reported with pedigree charts.

Results:

Multiple patterns of consanguineous marriages in tribal and nontribal populations were observed. ID was found to be associated in children with their relatives of the first, second, and third generations.

Conclusion:

ID may inherit in individuals from their relatives of the first, second, and third generations who have ID, epilepsy, or mental illness and married in the relationship. Appropriate knowledge, guidance, and counseling may be provided to potential couples before planning a consanguineous marriage.

Contribution of Inbred Singletons to Variance Component Estimation of Heritability and Linkage

OBJECTIVES

An interesting consequence of consanguinity is that the inbred singleton becomes informative for genetic variance. We determine the contribution of an inbred singleton to variance component analysis of heritability and linkage.

METHODS

Statistical theory for the power of variance component analysis of quantitative traits is used to determine the expected contribution of an inbred singleton to likelihood-ratio tests of heritability and linkage.

RESULTS

In variance component models, an inbred singleton contributes relatively little to a test of heritability but can contribute substantively to a test of linkage. For small-to-moderate quantitative trait locus (QTL) effects and a level of inbreeding comparable to matings between first cousins (the preferred form of union in many human populations), an inbred singleton can carry nearly 25% of the information of a non-inbred sib pair. In more highly inbred contexts available with experimental animal populations, nonhuman primate colonies, and some human subpopulations, the contribution of an inbred singleton relative to a sib pair can exceed 50%.

CONCLUSIONS

Inbred individuals, even in isolation from other members of a sample, can contribute to variance component estimation and tests of heritability and linkage. Under certain conditions, the informativeness of the inbred singleton can approach that of a non-inbred sib pair.

Whole exome sequencing unveils a frameshift mutation in CNGB3 for cone dystrophy: A case report of an Indian family

RATIONALE

Genetic elucidation of cone-dominated retinal dystrophies in Indian subcontinent is much needed to identify and catalog underlying genetic defects. In this context, the present study recruited a consanguineous Indian family affected with autosomal recessive cone dystrophy (CD). Considering the huge genetic heterogeneity and recessive inheritance of the disease, we chose to dissect out causal variant in this family by whole exome sequencing (WES).

PATIENT CONCERNS

In the recruited family, three of the six siblings had complaints of poor visual acuity, photophobia, and disturbed colour vision since early childhood. Fundus examination disclosed vascular attenuation and macular retinal pigment epithelium (RPE) changes in all the affected siblings, signifying degeneration of photoreceptor cells.

DIAGNOSIS

Complete clinical investigation and electroretinography studies led to the diagnosis of cone dystrophy in three siblings of the family.

INTERVENTIONS

Detailed ophthalmic examination, including family history, visual function testing, and retinal imaging, was performed. We captured and sequenced exomes of 2 affected siblings and their mother using SureSelect Human All Exon V5 Kit on Illumina HiSeq 2000/2500 platform with 100 bp paired-end sequencing method. Candidates after data analysis were screened by segregation analysis and Sanger sequencing. Considering recessive inheritance and consanguinity in the pedigree, we attempted to map large loci homozygous by descent in the genome of patients using exome sequencing variants. Extensive protein modeling was carried out to assess possible consequences of the identified variant on the 3-dimensional structure of the protein.

OUTCOMES

WES generated more than 65,000 variants for each individual. Assuming recessive inheritance, 13,026 variants were selected. Further filtering on the basis of their position in gene, class, and minor allele frequency constricted the huge list to 12 rare variants. Finally, we ascertained a single base deletion c.1148delC (p.Thr383fs) in the gene CNGB3 as the causal variant. This is a recurrent frameshift mutation resulting in truncated CNGB3 protein. We mapped a large 15-Mb stretch of homozygous markers spanning the causal variant in the proband. The gene CNGB3 encodes modulatory subunit of cyclic nucleotide-gated channels in cone photoreceptors. Protein modeling reveals loss of 2 transmembrane helices and conserved CAP_ED domain in truncated CNGB3, which eventually is predicted to form nonfunctional channels and hamper phototransduction.

LESSONS

We have identified a recurrent mutation c.1148delC (p.Thr383fs) in CNGB3 for autosomal recessive CD. The present report provides the first description of CNGB3 mutation from India. It is also the foremost investigation of familial CD in Indian patients; therefore, it presents the primary genetic etiology of CD in India.

Profiling β Thalassemia Mutations in Consanguinity and Nonconsanguinity for Prenatal Screening and Awareness Programme

Mutation spectrum varies significantly in different parts and different ethnic groups of India. Social factors such as preference to marry within the community and among 1st degree relatives (consanguinity) play an important role in impeding the gene pool of the disease within the community and so in society by and large. The present paper discusses the role of consanguinity in profiling of beta thalassemia mutation, and thus the approach for prenatal screening and prevention based awareness programme. Clinically diagnosed 516 cases of beta thalassemia were screened at molecular level. A detailed clinical Proforma was recorded with the information of origin of the family, ethnicity, and consanguinity. The present study reports that subjects originating from Uttar Pradesh, Uttarakhand, Bihar, and Jharkhand have c.92+5G>C and c.124_127delTTCT mutation as the commonest mutation compared to the subjects hailing from Madhya Pradesh and Chhattisgarh and Nepal where sickle mutation was found more common. In 40 consanguineous unions more common and specific beta mutations with higher rate of homozygosity have been reported. This consanguinity-based data helps not only in deciding target oriented prenatal diagnostic strategies but also in objective based awareness programmes in prevention of thalassemia major birth.

The genetic and environmental factors for keratoconus

Keratoconus (KC) is the most common cornea ectatic disorder. It is characterized by a cone-shaped thin cornea leading to myopia, irregular astigmatism, and vision impairment. It affects all ethnic groups and both genders. Both environmental and genetic factors may contribute to its pathogenesis. This review is to summarize the current research development in KC epidemiology and genetic etiology. Environmental factors include but are not limited to eye rubbing, atopy, sun exposure, and geography. Genetic discoveries have been reviewed with evidence from family-based linkage analysis and fine mapping in linkage region, genome-wide association studies, and candidate genes analyses. A number of genes have been discovered at a relatively rapid pace. The detailed molecular mechanism underlying KC pathogenesis will significantly advance our understanding of KC and promote the development of potential therapies.

Impact of consanguinity on cardio-metabolic health and other diseases: findings from an Afro-Indian tribal community

Numerous anthropological reports have indicated consanguineous marriage in populous Asian countries, but the overall impact of first cousin marriage on survival and health of specific communities has rarely been reported. The aim of the study was to estimate risks for various complex diseases in the progeny of consanguineous parents. A cross-sectional study was conducted among 222 women among Siddis, a particularly vulnerable tribal group in the state of Gujarat, India, who are Sunni Muslims by faith. The Siddis are not part of the original Negrito element of India. They are descendants of Africans from Northeast and East Africa who were brought to India as slaves, soldiers, or servants. The degree of consanguinity between each female and her spouse and the degree of consanguinity between their parents and proband's grandparents were recorded with the help of pedigrees. The results showed that the rate of consanguinity in the present generation was 49 % (N = 109), higher than preceding generations. A significant association was observed between women's age, educational level, occupational status, consanguineous parents, and consanguinity. Socioeconomic status and consanguinity showed U-shaped associations. Nearly three times odds for cardio-metabolic risks (2.65 odds ratio (OR) for heart diseases, 2.44 OR for diabetes mellitus, and 2.62 OR for hypertension) have been contracted in the progeny of consanguineous marriage in the parental generation. The risk of cardio-metabolic diseases is higher in offspring of consanguineous couples, and there is a significant increase in the prevalence of common adult diseases.

Is consanguinity prevalence decreasing in Saudis?: A study in two generations

BACKGROUND

Saudi population is unique in that there is a strong preference for cousin marriages in the general population. We studied the prevalence of consanguinity in educated Saudi females and compared the results with the results obtained in their parents, to access if a generation difference in which extensive educational activities have prevailed to inform the people of the influence of cousin marriages on health, has made any difference in prevalence of consanguineous marriages.

METHOD

A total of 600 Saudi women (421 university students and 179 women attending outpatients' clinics) were interviewed about their own and their parents' consanguinity.

RESULTS

The total consanguinity (first and second cousins) was 29.7% in the parents. Consanguinity was significantly higher among the daughters than the parents, where 37.9% of the 293 married women had consanguineous marriages. The prevalence of consanguinity was studied in different age groups, though no significant pattern was observed. A strong correlation was found between consanguinity of parents and their daughters; consanguinity was highest (52.3%) in the daughters of parents who were themselves consanguineous.

CONCLUSION

The results did not reveal any decrease in the prevalence of consanguinity over a generation. This shows that the tradition of marrying within the family is a preferred practice, despite the awareness that certain genetic disorders occur at a higher frequency in cousin marriages. There is a need at the primary health care level to inform the public of the consequences of this common practice.

The Prevalence Of β-Thalassemia Mutations in South Western Maharashtra

Thalassemia has been recognized by the World Health Organization as important inherited disorders principally impacting on the populations of low income countries. In this report, the prevalence of common β-thalassemia mutations in India was defined in 126 β-thalassemia carrier subjects in a western Indian population mainly from the south-western Maharashtra. The six most common β-thalassemia mutations were detected, which included IVS I-5 (G-C), IVS I-1 (G-T), codon 8-9 (+G), codon 41/42 (-TCTT), Codon 15 (G-A), and 619 bp deletion at 3' end of β-globin gene. These mutations accounted for 93.66 % in 126 β-thalassemia carrier subjects and 6.34 % remained uncharacterized. Out of 126, 82 (65.07 %) showed the most common (prevalent) type of mutation, IVS I-5 (G-C), followed by IVS I-1 (G-T) showed by 12 (9.52 %) subjects. Three (2.38 %) subjects showed 619 bp deletion, codon 8/9 (+G) and codon 15 (G-A) mutations were present in eight subjects each (6.34 %). Only five (3.96 %) subjects showed codon 41/42 (-TCTT). There were eight (6.34 %) subjects where mutation was not any of the six mutations studied. This study provides the pattern of β thalassemia mutations from south-western Maharashtra, which will help to prevent β-thalassemia using prenatal diagnosis and proper counseling.

Classification and regression tree and spatial analyses reveal geographic heterogeneity in genome wide linkage study of Indian visceral leishmaniasis

Background

Genome wide linkage studies (GWLS) have provided evidence for loci controlling visceral leishmaniasis on Chromosomes 1p22, 6q27, 22q12 in Sudan and 6q27, 9p21, 17q11-q21 in Brazil. Genome wide studies from the major focus of disease in India have not previously been reported.

Methods and Findings

We undertook a GWLS in India in which a primary ∼10 cM (515 microsatellites) scan was carried out in 58 multicase pedigrees (74 nuclear families; 176 affected, 353 total individuals) and replication sought in 79 pedigrees (102 nuclear families; 218 affected, 473 total individuals). The primary scan provided evidence (≥2 adjacent markers allele-sharing LOD≥0.59; nominal P≤0.05) for linkage on Chromosomes 2, 5, 6, 7, 8, 10, 11, 20 and X, with peaks at 6p25.3-p24.3 and 8p23.1-p21.3 contributed to largely by 31 Hindu families and at Xq21.1-q26.1 by 27 Muslim families. Refined mapping confirmed linkage across all primary scan families at 2q12.2-q14.1 and 11q13.2-q23.3, but only 11q13.2-q23.3 replicated (combined LOD = 1.59; P = 0.0034). Linkage at 6p25.3-p24.3 and 8p23.1-p21.3, and at Xq21.1-q26.1, was confirmed by refined mapping for primary Hindu and Muslim families, respectively, but only Xq21.1-q26.1 replicated across all Muslim families (combined LOD 1.49; P = 0.0045). STRUCTURE and SMARTPCA did not identify population genetic substructure related to religious group. Classification and regression tree, and spatial interpolation, analyses confirm geographical heterogeneity for linkages at 6p25.3-p24.3, 8p23.1-p21.3 and Xq21.1-q26.1, with specific clusters of families contributing LOD scores of 2.13 (P = 0.0009), 1.75 (P = 0.002) and 1.84 (P = 0.001), respectively.

Conclusions

GWLS has identified novel loci that show geographical heterogeneity in their influence on susceptibility to VL in India.

A descriptive profile of β-thalassaemia mutations in India, Pakistan and Sri Lanka

Thalassaemia is a common and debilitating autosomal recessive disorder affecting many populations in South Asia. To date, efforts to create a regional profile of β-thalassaemia mutations have largely concentrated on the populations of India. The present study updates and expands an earlier profile of β-thalassaemia mutations in India, and incorporates comparable data from Pakistan and Sri Lanka. Despite limited data availability, clear patterns of historical and cultural population movements were observed relating to major β-thalassaemia mutations. The current regional mutation profiles of β-thalassaemia have been influenced by historical migrations into and from the Indian sub-continent, by the development and effects of Hindu, Buddhist, Muslim and Sikh religious traditions, and by the major mid-twentieth century population translocations that followed the Partition of India in 1947. Given the resultant genetic complexity revealed by the populations of India, Pakistan and Sri Lanka, to ensure optimum diagnostic efficiency and the delivery of appropriate care, it is important that screening and counselling programmes for β-thalassaemia mutations recognise the underlying patterns of population sub-division throughout the region.

Profiling β-thalassaemia mutations in India at state and regional levels: implications for genetic education, screening and counselling programmes

Thalassaemia and sickle cell disease have been recognized by the World Health Organization as important inherited disorders principally impacting on the populations of low income countries. To create a national and regional profile of β-thalassaemia mutations in the population of India, a meta-analysis was conducted on 17 selected studies comprising 8,505 alleles and offering near-national coverage for the disease. At the national level 52 mutations accounted for 97.5% of all β-thalassaemia alleles, with IVSI-5(G>C) the most common disease allele (54.7%). Population stratification was apparent in the mutation profiles at regional level with, for example, the prevalence of IVSI-5(G>C) varying from 44.8% in the North to 71.4% in the East. A number of major mutations, such as Poly A(T>C), were apparently restricted to a particular region of the country, although these findings may in part reflect the variant test protocols adopted by different centres. Given the size and genetic complexity of the Indian population, and with specific mutations for β-thalassaemia known to be strongly associated with individual communities, comprehensive disease registries need to be compiled at state, district and community levels to ensure the efficacy of genetic education, screening and counselling programmes. At the same, time appropriately designed community-based studies are required as a health priority to correct earlier sampling inequities which resulted in the under-representation of many communities, in particular rural and socioeconomically under-privileged groups.

ELECTRONIC SUPPLEMENTARY MATERIAL

The online version of this article (doi:10.1007/s11568-010-9132-3) contains supplementary material, which is available to authorized users.

Risk factors according to estrogen receptor status of breast cancer patients in Trivandrum, South India

Estrogen receptor (ER) status is an important biomarker in defining subtypes of breast cancer differing in antihormonal therapy response, risk factors and prognosis. However, little is known about association of ER status with various risk factors in the developing world. Our case-control study done in Kerala, India looked at the associations of ER status and risk factors of breast cancer. From 2002 to 2005, 1,208 cases and controls were selected at the Regional Cancer Center (RCC), Trivandrum, Kerala, India. Information was collected using a standardized questionnaire, and 3-way analyses compared ER+/ER- cases, ER+ cases/controls and ER- cases/controls using unconditional logistic regression to calculate odds ratios and 95% confidence intervals. The proportion of ER- cases was higher (64.1%) than ER+ cases. Muslim women were more likely to have ER- breast cancer compared to Hindus (OR = 1.48, 95% CI = 1.09, 2.02), an effect limited to premenopausal group (OR = 1.87, 95% CI = 1.26, 2.77). Women with higher socioeconomic status were more likely to have ER+ breast cancer (OR = 1.48, 95% CI = 1.11, 1.98). Increasing BMI increased likelihood of ER- breast cancer in premenopausal women (p for trend < 0.001). Increasing age of marriage was positively associated with both ER+ and ER- breast cancer. Increased breastfeeding and physical activity were in general protective for both ER+ and ER- breast cancer. The findings of our study are significant in further understanding the relationship of ER status and risk factors of breast cancer in the context of the Indian subcontinent.

Diverse genetic origin of Indian Muslims: evidence from autosomal STR loci

The origin and relationships of Indian Muslims is still dubious and are not yet genetically well studied. In the light of historically attested movements into Indian subcontinent during the demic expansion of Islam, the present study aims to substantiate whether it had been accompanied by any gene flow or only a cultural transformation phenomenon. An array of 13 autosomal STR markers that are common in the worldwide data sets was used to explore the genetic diversity of Indian Muslims. The austere endogamy being practiced for several generations was confirmed by the genetic demarcation of each of the six Indian Muslim communities in the phylogenetic assessments for the markers examined. The analyses were further refined by comparison with geographically closest neighboring Hindu religious groups (including several caste and tribal populations) and the populations from Middle East, East Asia and Europe. We found that some of the Muslim populations displayed high level of regional genetic affinity rather than religious affinity. Interestingly, in Dawoodi Bohras (TN and GUJ) and Iranian Shia significant genetic contribution from West Asia, especially Iran (49, 47 and 46%, respectively) was observed. This divulges the existence of Middle Eastern genetic signatures in some of the contemporary Indian Muslim populations. Our study reveals that the spread of Islamic faith in the Indian subcontinent was predominantly cultural transformation associated with minor gene flow from West Asia.

Consanguineous unions and child health in the State of Qatar

The aim of the study was to estimate the prevalence and sociodemographic predictors of consanguineous unions in the State of Qatar and to assess the association between consanguinity, fertility and child health. A representative sample of 1800 Qatari women aged > or =15 years was approached for the study. Of these, 1515 (84.2%) women agreed to participate. The consanguineous marriage rate was 54.0% with estimated population confidence limits of 52.3-55.7%. First cousin unions were the most common form of cousin marriage. The level of parental consanguinity (both in the respondent's parents and her parents-in-law) was quite high. In a multivariable analysis, both education of the respondent and her husband as well as parental consanguinity were found to be strong predictors of consanguineous unions in the index generation. Although fertility was high in both groups, the mean number of pregnancies was somewhat higher in respondents with first cousin unions. Concomitantly they also had a slighter higher rate of livebirths than women in non-consanguineous unions. The occurrence of asthma, mental retardation, epilepsy and diabetes was significantly more common in offspring of all consanguineous than non-consanguineous couples.

Population stratification and genetic association studies in South Asia

Population stratification and its influence on genetic association studies is a controversial topic. Although it has been suggested that stratification is unlikely to bias the results of association studies conducted in developed countries, convincing contrary empirical evidence has been published. However, it is in populations where historical ethnic, religious and language barriers exist that community subdivisions will predictably exert greatest genetic effect, and influence the organization of association studies. In many of the populations of the Indian sub-continent, these basic population divisions are compounded by a strict tradition of intra-community marriage and by marriage between close biological relatives. Data on the very significant levels of genetic diversity that characterize the populations of India and Pakistan, with some 50,000-60,000 caste and non-caste communities in India, and average first cousin marriage rates of 40%-50% in Pakistan, are presented and discussed. Under these circumstances, failure to explicitly control for caste/biraderi membership and the presence of consanguinity could seriously jeopardize, and may totally invalidate, the results of association/case control studies and clinical trials.

Awareness about problems associated with consanguineous marriages: survey among Israeli Arab adolescents

PURPOSE

To evaluate the level of knowledge among adolescents about the issues associated with consanguinity, because consanguineous marriages are widely practiced among Arabs, and are associated with an increased incidence of congenital malformations.

METHODS

We carried out a national survey among 2933 students aged 15-16 years within the Israeli Arab community. Variables considered were gender, religion, location of residence, parents' level of education, number of siblings, whether their parents' marriage was consanguineous, whether any family members had congenital malformations, and the respondents' religious beliefs and traditions. Association among those variables and the level of knowledge that were statistically significant by univariate analysis were also assessed in a multivariate model.

RESULTS

One-quarter of the students (24.5%) demonstrated a high level of knowledge, whereas 29.7% had a moderate level and 45.8% a low level. Overall, 81.5% knew that consanguinity was associated with a high incidence of congenital malformations, although only half of these (50.0%) knew what congenital malformations were and which were associated with consanguinity. The variables significantly associated with a low level of knowledge were gender, level of parents' education, consanguinity between the students' parents, and extreme religious attitudes.

CONCLUSIONS

Efforts to increase the knowledge of Israeli Arab adolescents about consanguinity should therefore be especially directed toward males with parents who have a lower level of education, with parents who are consanguineous, and who have extreme religious attitudes.

Does heterozygosity estimate inbreeding in real populations?

Many recent studies report that individual heterozygosity at a handful of apparently neutral microsatellite markers is correlated with key components of fitness, with most studies invoking inbreeding depression as the likely underlying mechanism. The implicit assumption is that an individual's inbreeding coefficient can be estimated reliably using only 10 or so markers, but the validity of this assumption is unclear. Consequently, we have used individual-based simulations to examine the conditions under which heterozygosity and inbreeding are likely to be correlated. Our results indicate that the parameter space in which this occurs is surprisingly narrow, requiring that inbreeding events are both frequent and severe, for example, through selfing, strong population structure and/or high levels of polygyny. Even then, the correlations are strong only when large numbers of loci (~200) can be deployed to estimate heterozygosity. With the handful of markers used in most studies, correlations only become likely under the most extreme scenario we looked at, namely 20 demes of 20 individuals coupled with strong polygyny. This finding is supported by the observation that heterozygosity is only weakly correlated among markers within an individual, even in a dataset comprising 400 markers typed in diverse human populations, some of which favour consanguineous marriages. If heterozygosity and inbreeding coefficient are generally uncorrelated, then heterozygosity-fitness correlations probably have little to do with inbreeding depression. Instead, one would need to invoke chance linkage between the markers used and one or more gene(s) experiencing balancing selection. Unfortunately, both explanations sit somewhat uncomfortably with current understanding. If inbreeding is the dominant mechanism, then our simulations indicate that consanguineous mating would have to be vastly more common than is predicted for most realistic populations. Conversely, if heterosis provides the answer, there need to be many more polymorphisms with major fitness effects and higher levels of linkage disequilibrium than are generally assumed.

Endogamy, consanguinity and community genetics

The population of India is composed of many thousands of subpopulations, divided by geography, language, religion and caste or biraderi (patrilineage) boundaries, with endogamous marriage the norm. The net effect has been the creation of multiple genetic isolates with individual mutation profiles, but to date the clinical consequences of this highly complex differentiation have been largely ignored. In contrast, the topic of consanguinity continues to attract attention among medical and population geneticists, clinicians and social scientists. The significant progress made in India in improving childhood nutritional status and combating infectious disease means that genetic disorders have assumed ever-increasing importance. In populations where consanguineous marriage is widely practised, recessive genetic disorders will continue to gain greater prominence in the overall spectrum of ill health. At the same time this increase will in part be negated by urbanization and the move to smaller family sizes, which predictably will result in a decline in the prevalence of consanguineous unions. Developing an understanding of these changes will require a wide-ranging and multidisciplinary investigative approach for which community genetics is ideally suited.

Consanguinity and Ocular Genetic Diseases in South India: Analysis of a Five-Year Study

OBJECTIVE

Consanguineous marriage is a widely practised social custom in Asia and northern Africa. In south India, Dravidian Hindus have contracted consanguineous marriages for over 2,000 years. In the present study, the influence of consanguinity on the prevalence of visual disorders was examined in patients attending a specialist genetic eye clinic.

SUBJECTS AND METHODS

A total of 2,335 patients attending Sankara Nethralaya, Chennai, India, were screened for genetic eye disorders over a five-year period. The patients were drawn from all parts of India and from neighbouring countries in south Asia.

RESULTS AND DISCUSSION

Six hundred and seventy-three (28.8%) of the patients tested for ophthalmic genetic disorders reported a family history of consanguinity. The majority (n = 574) of these families were from south India. In the patient group as a whole, the most common form of consanguineous union was between first cousins (n = 367), followed by uncle/niece marriage (n = 177), equivalent to a mean coefficient of inbreeding alpha = 0.0202. Among the consanguineous families, 430 of 673 (63.9%) had retinitis pigmentosa, 167 of these cases were autosomal recessive and 199 were isolated cases. The public in regions such as south India should be made aware of the merits and demerits of consanguineous marriages.

Consanguinity and early mortality in the Muslim populations of India and Pakistan

Empirical information from studies conducted in Pakistan has indicated a high level of offspring mortality that can be attributed to parental consanguinity even when non-biological variables are controlled. However, with the exception of some small and geographically restricted studies, few comparable data are available on the influence of inbreeding in child survival among the Muslim population of India, which numbers between 100 and 120 million. The present study compares deaths during the first 5 years of life among the offspring of first cousin (F = 0.0625) and non-consanguineous unions (F = 0), using data collected in the 1992-1993 Indian National Family Health Survey (NFHS) and the 1990-1991 Pakistan Demographic and Health Survey (PDHS). The focus was on determinants of mortality in live-born children to age 5 years. In both countries, bivariate analyses indicated that mortality was significantly increased in the offspring of first cousin unions during the neonatal and post-neonatal, total infant, and under-5 year periods. The findings were confirmed by multivariate regression, which incorporated control for a range of biological and demographic factors.

Evolution of consanguinity in the Bishopric of Lugo (Spain) from 1900 to 1979

BACKGROUND

The levels of consanguinity in human populations are known to be influenced by demographic and geographical factors, and by socio-cultural customs that govern spouse choice. Within the general model applicable to the populations of Western Europe, Galicia (north-west Spain) is a region that is especially interesting, due to its geographical and historical peculiarities that could have conditioned its behaviour pattern with respect to consanguinity.

PRIMARY OBJECTIVE

The object of this paper is to analyse the evolution of the consanguinity structure levels in the rural population of the Bishopric of Lugo (Galicia) during the period 1900-1979.

SUBJECTS AND METHODS

The study covers a total of 752 parishes included in 52 municipalities of the rural area of the Bishopric of Lugo. Of a total of 117,583 marriages in the period studied, 6701 were between biologically related individuals up to the level of second cousins. The percentage of the different types of consanguineous marriages, the consanguinity rates, and the average coefficient of inbreeding of the population was calculated. Also, for the analysis of the temporal variation of consanguinity, version 3.01 of Jandel Scientific's Table Curve program was used.

MAIN OUTCOMES AND RESULTS

The consanguinity rate for the whole of the period is 5.70% and the average coefficient of inbreeding is 2.2477 x 10(-3), values which fall within the observed range for Spanish populations. As for the consanguinity structure, the most frequent types of consanguineous marriages are between second cousins (2.65% of all marriages), but the high proportion of marriages between uncles/nieces or aunts/nephews (0.16%) and first cousins (2.12%) with regard to the total number of marriages should be emphasized. The average value of the M22/M33 ratio is 0.80, and throughout the study period it was above the 0.25 expected in conditions of panmixia. Regarding the evolution of the average coefficient of inbreeding, its annual values fit a polynomial regression curve with one ascending and one descending branch and an inflection point in the year 1919.

CONCLUSIONS

As in other rural areas of Galicia, the structure of consanguinity in the Bishopric of Lugo is characterized by the high proportion of marriages between uncles/nieces or aunts/nephews and first cousins, a phenomenon which appears to be generalized in the rural populations of northern Spain. It is suggested that the high proportion of uncle/niece marriages that have been found in the population studied are very probably due to the important migratory phenomenon which took place in this region at the end of the 19th century and in the first third of the 20th century.