THE EFFECT OF CONSANGUINITY ON CONGENITAL DISABILITIES IN THE KUWAITI POPULATION
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Consanguinity has been shown to increase homozygosity and to reduce genetic variation in a group, which may protect against the expression of recessive genes that can lead to genetic disorders. Consanguineous marriages are practised widely in Kuwait. The major aim of this study is to delineate the association of consanguineous marriages with congenital disabilities in different Kuwaiti population subcultures. A total of 9104 married Kuwaiti females aged 15-79 years from different backgrounds were selected at ten primary health care centres from six governorates in Kuwait. Data were collected using a questionnaire and analysed with chi-squared tests. The data indicate significant differences in the occurrence of genetic diseases in consanguineous couples' offspring (4.88%) compared with those of non-consanguineous couples (4.13%) (p<0.002). The results also show significant differences in frequencies of genetic/environmental diseases in consanguineous couples' offspring (8.59%) compared with those of non-consanguineous couples (8.23%) (p<0.005). No significant differences between the two groups regarding environmental diseases were observed. A higher frequency of genetic diseases was found in first- (6.97%; p<0.001), second- (6.78%; p<0.001) and third-cousin (6.46%; p<0.022) couples' offspring compared with those of non-consanguineous couples. The frequency of congenital disabilities in the offspring of couples from consanguineous marriages (2.9%) is higher than that in the offspring of non-consanguineous marriages (2.3%). But this difference is not significant at the 0.05 level. First-cousin marriages have the highest frequency (3.5%) of congenital disabilities compared with other kinds of marriages (2.1-2.3%). Differences across groups are significant (p<0.036). Significant differences are found for first-cousin couples in both physical (2.37; p<0.042) and mental (0.74; p<0.037) disabilities compared with non-consanguineous couples. No significant differences were observed in deafness and blindness disabilities. The data show no significant differences between second- and third-cousin and non-consanguineous couples in physical, mental or deafness and blindness disabilities. There are no significant differences in the percentages of offspring with congenital disabilities in consanguineous and non-consanguineous marriages across sub-population groups for the total of four types of congenital disability.Keywords:
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To test the effects of parental consanguinity on mortality among offspring, inbreeding coefficients were estimated for 303,675 members of the Utah Mormon population who were born between 1847 and 1945. Although consanguinity has been relatively rare in this population, the large sample size permitted the identification of more than 3,500 inbred offspring. Among the offspring of unrelated parents, 13.2% died before the age of 16. Significant elevations in prereproductive mortality were seen among the offspring of first-cousin marriages (22%) and among the offspring of closer unions (32%). The cor- responding relative risks are 1.70 (95% confidence limits = 1.52, 1.91) and 2.41 (95% confidence limits = 1.59, 3.41), respectively. Other categories of relationship did not produce significant elevations in offspring mortality. Similar results were obtained when a case-control approach was used to remove the effects of socioeconomic variation. Consistent with many other studies of populations with low consanguinity rates, this population experienced a relatively high absolute increase in mortality among the offspring of first-cousin marriages (9%). Preliminary evidence is offered for the hypothesis that mortality differentials are larger in populations with low inbreeding and low mortality because nongenetic causes of death do not obscure the effects of consanguinity.
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Consanguinity has been shown to increase homozygosity and to reduce genetic variation in a group, which may protect against the expression of recessive genes that can lead to genetic disorders. Consanguineous marriages are practised widely in Kuwait. The major aim of this study is to delineate the association of consanguineous marriages with congenital disabilities in different Kuwaiti population subcultures. A total of 9104 married Kuwaiti females aged 15-79 years from different backgrounds were selected at ten primary health care centres from six governorates in Kuwait. Data were collected using a questionnaire and analysed with chi-squared tests. The data indicate significant differences in the occurrence of genetic diseases in consanguineous couples' offspring (4.88%) compared with those of non-consanguineous couples (4.13%) (p<0.002). The results also show significant differences in frequencies of genetic/environmental diseases in consanguineous couples' offspring (8.59%) compared with those of non-consanguineous couples (8.23%) (p<0.005). No significant differences between the two groups regarding environmental diseases were observed. A higher frequency of genetic diseases was found in first- (6.97%; p<0.001), second- (6.78%; p<0.001) and third-cousin (6.46%; p<0.022) couples' offspring compared with those of non-consanguineous couples. The frequency of congenital disabilities in the offspring of couples from consanguineous marriages (2.9%) is higher than that in the offspring of non-consanguineous marriages (2.3%). But this difference is not significant at the 0.05 level. First-cousin marriages have the highest frequency (3.5%) of congenital disabilities compared with other kinds of marriages (2.1-2.3%). Differences across groups are significant (p<0.036). Significant differences are found for first-cousin couples in both physical (2.37; p<0.042) and mental (0.74; p<0.037) disabilities compared with non-consanguineous couples. No significant differences were observed in deafness and blindness disabilities. The data show no significant differences between second- and third-cousin and non-consanguineous couples in physical, mental or deafness and blindness disabilities. There are no significant differences in the percentages of offspring with congenital disabilities in consanguineous and non-consanguineous marriages across sub-population groups for the total of four types of congenital disability.
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Results: The results showed that, in 61.4 % of people, consanguinity was present, which, first cousin consanguineous marriage was found among the parents of 43.6 % of the students and second cousin consanguinity was present in 17.9 % of them and there was significant relation between consanguineous marriage and having more than one disabled children in the family, as, 77.7% persons who had more than one handicapped child, had consanguineous marriage. Conclusion: According to prevalence of hearing impairment in consanguineous marriage that was measured 61.4% in this study, therefore, it seems essential, the prevention of hereditary hearing impairment. Consanguineous marriages is one of the cultural problems at present time, that may lead to some inherited disorders like hearing impairment; so we should give enough information about the risk of consanguinity and its related outcomes to the involved people.
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The present study focuses on the effect of parental consanguinity on genetic disorders in the Iranian population, which is predominantly Muslim and where consanguineous marriages are quite common. Data were collected from three genetic centers from different areas of Tehran. Out of 800 affected subjects nearly 44% were born to consanguineous parents. While 37.8% of them were born out of parallel- cousin marriages, 28.9% were from cross- cousin alliances. Frequency of occurrence of genetic disorders was twice in children born to parallel-cousin parents as compared with those occurring out of cross-cousin marriages. Psychomotor retardation (14.3%), primary amenorrhoea (11.2%), and mental retardation (6.6%) topped the list of disorders encountered in children born to consanguineous parents. Cases of phenylketonuria were encountered exclusively in children of consanguineous couples. Of the patients having positive family history of genetic disorders, 93% had consanguineous parents. Two points emerge from the present study: that related parents, whatsoever the relationship, are more likely to have children with genetic defects; consanguineous couples who already have an affected child are 13 times more likely to have another affected child.
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Summary. Most studies on consanguinity have been conducted on contemporary populations and have focused on the prevalence and types of preferred intra-familial marriage. With its comprehensive birth, marriage and deaths records dating back to the late 17th century, and the legal bar on first cousin marriage removed in the mid-19th century, Sweden offers unique opportunities to examine the factors that determine by whom, where and why consanguineous marriages were contracted. The present study covers the period 1780–1899 and presents a detailed portrait of cousin and sibling exchange marriages in the Skelleftea region of northern coastal Sweden. The combined prevalence of first, second and third cousin marriage increased from 2.3% in 1790–1810 to 8.8% in 1880–1899, and multi-generation consanguinity also increased significantly over the study period. The distribution and prevalence of first cousin marriages was strikingly non-random, with a significantly greater propensity for consanguinity among land-owning families, especially involving first-born sons, within specific pedigrees, and in a number of more remote inland communities. Additional factors associated with a greater likelihood of consanguineous marriage included physical or mental disability among males, and among females the prior birth of an illegitimate child. Besides the inherent interest in the social and demographic structure of this region of northern Sweden during the course of the 19th century, in future studies it will be important to determine the degree to which the observed patterns of consanguineous and sibling exchange marriages in these past generations could have influenced present-day genetic structure.
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Summary A high occurrence rate of consanguineous marriages may favour the onset and increased frequency of autosomal recessive diseases in a population. The population of Monte Santo, Bahia, Brazil, has a high frequency of rare genetic diseases such as mucopolysaccharidosis type VI, whose observed frequency in this population is 1:5000, while the incidence of this disease recorded in other regions of the world varies from 1:43,261 in Turkey to 1:1,505,160 in Switzerland. To verify the influence of consanguineous marriage on the increased frequency of observed genetic diseases in this population, the population structure and frequency of different types of marriage during different time periods were evaluated. A total of 9765 marriages were found in an analysis of parish marriage records from the city. Over three periods, 1860–1895, 1950–1961 and 1975–2010, the inbreeding rates were 37.1%, 13.2% and 4.2% respectively. Although there was a high rate of inbreeding, endogamic marriages were the dominant marriage type in all three periods. In the most recent period, there was an increase in the number of exogamous marriages and those among immigrants, but most of these occurred among individuals from cities that neighbour Monte Santo. The low rate of migration and high frequency of endogamic and consanguineous marriages show that growth of this population is predominantly internal and could explain the occurrence, and increase in frequency, of recessive genetic diseases in the city.
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The study was performed in six mohallahs (colonies) of Aligarh City (North India). All six mohallahs are predominantly inhabited by Qureshi (meat sellers, a highly endogamous group) Muslims. A total of 1721 infants and children up to the age of 6 years were examined to determine the incidence of congenital heart diseases (CHD) in relation to the degree of consanguinity of the parents. Around 43% of the subjects were the offspring of consanguineous marriages including second‐cousin, first‐cousin‐once‐removed and first‐cousin. A higher percentage of CUD was found in the offspring of consanguineous marriages: about 3.37% out of 741 children as compared to 1.22% in 980 offspring of non‐consanguineous marriages, whereas in the first‐cousin offspring, the percentage of CHD rose to 4.41%. The differences were found to be statistically significant. The present study suggests a genetic influence and also casts doubt on the applicability of a polygenic threshold model to all forms of cardiac malformation.
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Summary In genetics, a consanguineous marriage means union between couples who are related as second cousins or closer. The present cross-sectional study was carried out in order to illustrate the prevalence and types of consanguineous marriages in the Shi'a population living in widespread territories in Lebanon including the Bekaa Valley, the south of Lebanon and the southern suburb of Beirut. Data on types of marriages were collected using a simple questionnaire. The total number of couples in the study was 1203. Consanguineous marriage was classified by the degree of relationship between couples. The overall frequency of consanguinity was found to be 28.4%, with first cousin marriages (21.3%) being the most common type followed by first cousins once removed (5.5%), then double first cousins (0.8%). The frequencies of second cousin and beyond second cousin marriages were the same at 0.4% of all the marriages. The mean inbreeding coefficient ( α ) was estimated at about 0.0161 for the population. There were no significant differences between the three studied territories for frequencies of different types of marriages ( p >0.1), nor were there significant differences between the rural and urban areas ( p >0.1).
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The objective of this study was to explore the secular trend in consanguinity in Jordan and the subtypes of consanguineous marriages that may be undergoing a change. A total of 1032 individuals attending a diabetic clinic in Amman were interviewed. The questionnaire provided information on consanguinity status and date of marriage among three generations: the persons interviewed, their parents, parents of their spouses and their offspring. Data on consanguinity status among 5401 marriages was obtained. Generations were named generation 1 for marriages contracted before 1950, generation 2 for marriages contracted between 1950 and 1979, and generation 3 for marriages contracted after 1980. For generations 1, 2, and 3, first-cousin marriages constituted 20.2, 28.5 and 19.5% of all marriages, respectively, while the subtype of paternal parallel first-cousin marriages constituted 75.6, 60.3 and 43.3% of all first-cousin marriages, respectively. The offspring of first-cousin parents were significantly more prone to marry their relatives than the offspring of non-consanguineous parents, with rates of first-cousin marriages among offspring of first-cousin parents and non-related parents constituting 25.3 and 17.1% of all marriages, respectively. For generations 1, 2 and 3, the average coefficient of inbreeding was 0.0135, 0.02 and 0.0142, respectively. In conclusion, first-cousin marriage rate among a representative population from Amman showed a significant decline among marriages contracted after 1980 compared to marriages contracted between 1950 and 1979, but not to marriages contracted before 1950. The proportion of paternal parallel first cousins among first-cousin marriages showed a steady decline from one generation to the next.
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