Consanguineous marriage in the capital city Sana'a, Yemen

Consanguineous marriage is traditionally common throughout the Eastern Mediterranean region, especially in the mainly Muslim countries. To date, there is little information on consanguinity in Yemen. The aim of this study was to ascertain the rate of consanguineous marriage and average coefficient of inbreeding in Sana'a City, Yemen. A population survey was conducted with the intention of covering married couples resident in Sana'a City by means of a multi-stage random sampling technique. A total of 1050 wives and husbands were interviewed on consanguinity in their households. The total incidence of consanguinity was 44-7% (95% CI 41.7-47.7%) with first-cousin marriages constituting 71.6% of the total consanguineous marriages and 32% of all marriages. Paternal parallel first cousins (Type I) accounted for 49% of first-cousin marriages. The average coefficient of inbreeding (F) was 0.02442. The incidence of consanguinity is relatively high in Yemen with predominantly first-cousin marriage. This might be related to the deeply rooted social and cultural beliefs in the country.     

Inbreeding in Finland

We have compiled data on the frequency of first-cousin marriages in Finland using royal dispensation records for the time period 1810-1872 and national population statistics for the time period 1878-1920. For the earlier period, 0.315% of Finland's marriages were contracted between first cousins (2,331 of 739,387). During the second time period, 0.174% of Finland's marriages took place between first cousins (1,325 of 761,976). These figures, which yield average kinship coefficients of 0.00020 and 0.00011, respectively, show that the level of inbreeding in Finland due to first-cousin marriage has been quite low. An analysis of individual parishes shows that first-cousin marriages are, on average, substantially less frequent than predicted by a random-mating model. In order to evaluate determinants of first-cousin marriage, several predictive variables have been examined: parish ethnic composition (proportion of Swedish and Finnish speakers), husband's occupation (graded into 6 socioeconomic levels), geographic distance between spouses' premarital residences, population density, parish endogamy, and urban vs. rural residence. Various logistic and linear regression models were analyzed in which consanguinity was the dependent variable. The best predictors of consanguinity were ethnic composition and occupation. The other variables were not in general significant predictors. These results show that many of the "mate availability" factors that would be predicted theoretically to account for consanguinity variation (population density, geographic isolation, urban vs. rural residence) do not. Instead, the best predictors of consanguinity at the first-cousin level are cultural factors such as ethnicity and occupation. Evaluation of cultural variables can provide a greatly enriched interpretation of complex biosocial phenomena such as inbreeding.     

Frequency of first-cousin marriages from civil marriage certificates in Argentina

In Argentina information concerning relatedness of mates, especially first cousins, was introduced into the legal marriage certificate, record, and statistical report in 1968. The 1980-1981 biennial data, including 212,320 legal marriage reports, were analyzed for all of Argentina, subdivided into 22 states and 494 counties. The registered 0.373% of first-cousin marriages allows an estimate of consanguineous marriages of 0.629% and a mean inbreeding coefficient of alpha = 0.00031. This estimate lies between the observed alpha = 0.00011 from hospital births and alpha = 0.00052 from Roman Catholic Church dispensations. These differences are not large, and they may be due to sampling variations, indicating a low rate of inbreeding in Argentina. The frequency of first-cousin marriages in the 22 Argentine states is heterogenous, and 9 counties, representing 5 different regions, were identified as having a high rate of first-cousin marriage. Three of these were previously known as genetic isolates. A second series of data, including all 32,690 legal marriages registered in the state of Buenos Aires during the first half of 1984, showed a frequency of first-cousin marriages of 0.677%. First-cousin mates, compared with non-first-cousin mates, had a higher frequency of both mates being born in the same state of Buenos Aires and similar frequency distributions for age at marriage, single previous marriage status, level of education, and rate of unemployment. It is concluded that legal marriage data on consanguinity is reliable, inexpensive, universal, and enduring. The last two characteristics make them suitable for the survey of geographic clusters and time trends.     

Ancestral consanguinity and mortality among three endogamous populations of Chittoor District, Andhra Pradesh, India

Consanguineous marriages have been practiced around the globe by many societies from time immemorial, particularly in South India. Consanguineous marriages play a major role in the health of a population, and diseases leading to mortality of the progeny are a consequence of detrimental recessive genes. To evaluate the effects of ancestral consanguinity on mortality in relation to consanguineous marriage, we have ascertained data from 1,500 women belonging to three endogamous communities (Akuthota Reddy, Odde, and Madiga) of Chittoor District, Andhra Pradesh, India. There were 500 women from each community. For each marriage we drew a family pedigree, extended upward to two earlier generations on either side of the spouses, to determine the prevalence and pattern of consanguinity, with detailed information on fertility and mortality. We observed a significant difference in the mortality rates between consanguineous and nonconsanguineous marriages when all the marriages of the women, women's parents, and (women's) husband's parents were considered in all three communities. In inbreeding, the offspring of earlier generations might have passed on deleterious genes to later generations (under unfavorable conditions), which resulted in a negative aspect of reproduction (among the offspring of the present couple).     

Parental consanguinity as a cause for increased incidence of births defects in a study of 238,942 consecutive births.

The risk for birth defects in the offspring of first-cousin matings has been estimated to increase sharply compared to non consanguineous marriages. As a general decline in the frequency of consanguineous marriages was observed in this century, one wonders whether consanguinity is still a factor in the appearance of birth defects in developed countries. Based on our registry of congenital anomalies we tried to answer to this question. In the population studied in North-Eastern France a consanguineous mating was known in 1.21% of the cases with congenital anomalies, vs. 0.27% in controls, (p < 0.001). The frequency of the malformations recorded paralleled the degree of consanguinity: out of 89 malformed children, 51 were seen in first-cousins mating (10.3 times more frequent than in offspring of non consanguineous couples), 17 in second-cousins marriages and 18 in more distant relatives mating. Three were uncle-niece marriage. Excluding known mendelian conditions these numbers were 73, 36, 17 and 17 respectively and the corresponding relative risk were 3.68, 3.01, 3.41 and 4.89 respectively. Therefore there is a negative dose-response effect between level of inbreeding and risk of congenital malformations. Consanguineous mothers were more often pregnant than non consanguineous mothers (p < 0.01) and they had more stillbirths than non consanguineous mothers. These results show that consanguinity is still a factor of birth defects and they must be taken into account for genetic counseling of inbred marriages, in developed countries.     

The Effect of Inbreeding on Mortality and Morbidity among Telugu-speaking Populations of Kharagpur, West Bengal, India

Increased mortality and morbidity including congenital malformations among the offspring of consanguineous marriages have been widely reported in human populations from different parts of the world. However, there are few studies on the effect of the intensity of inbreeding and different degrees of inbreeding on mortality and morbidity. The present study is an attempt to examine the effects of inbreeding on mortality and morbidity including congenital disorders in different levels of inbreeding among Telugu-speaking populations of Kharagpur, West Bengal, India, based on data collected through extensive pedigrees. The study reveals that the frequency of spontaneous abortions and stillbirths is higher in the offspring of consanguineous marriages than in that of non-consanguineous marriages. A similar effect is also observed in the infant mortality rate, which is known to have a genetic component, but is not seen in the mortality rate of children and juveniles. The rate of morbidity is consistently higher in the offspring of consanguineous marriages with a sex bias in favour of inbred females. The increased morbidity rates in inbred individuals tend to be inversely correlated with the increase in average autosomal inbreeding coefficient. This appears to strengthen Sanghvi’s hypothesis of a decline in the frequency of deleterious genes with intensification of inbreeding through generations. The present study also confirms an increase in genetic disorders with an increase in inbreeding in almost all populations.     

Consanguineous marriages in Afghanistan

The present cross-sectional study was done in order to illustrate the prevalence and types of consanguineous marriages among Afghanistan populations. Data on types of marriages were collected using a simple questionnaire. The total number of couples in the study was 7140 from the following provinces: Badakhshan, Baghlan, Balkh, Bamyan, Kabul, Kunduz, Samangan and Takhar. Consanguineous marriages were classified by the degree of relationship between couples: double first cousins, first cousins, first cousins once removed, second cousins and beyond second cousins. The coefficient of inbreeding (F) was calculated for each couple and the mean coefficient of inbreeding (α) estimated for each population. The proportion of consanguineous marriages in the country was 46.2%, ranging from 38.2% in Kabul province to 51.2% in Bamyan province. The equivalent mean inbreeding coefficient (α) was 0.0277, and ranged from 0.0221 to 0.0293 in these two regions. There were significant differences between provinces for frequencies of different types of marriages (p<0.001). First cousin marriages (27.8%) were the most common type of consanguineous marriages, followed by double first cousin (6.9%), second cousin (5.8%), beyond second cousin (3.9%) and first cousin once removed (1.8%). There were significant differences between ethnic groups for the types of marriages (χ2=177.6, df=25, p<0.001). Tajiks (Soni) and Turkmens (also Pashtuns) showed the lowest (α=0.0250) and highest (α=0.0297) mean inbreeding coefficients, respectively, among the ethnic groups in Afghanistan. The study shows that Afghanistan's populations, like other Islamic populations, have a high level of consanguinity.     

Geographic, demographic and inbreeding patterns in a Basque mountainous region of Guipuzcoa

The Goierri, a mountain region within the Basque Hills of Guipúzcoa, includes one of the most culturally controlled autochthonous populations within the Basque area, mainly from linguistic point of view. The effects of geography and demographic changes (1862–1995) on consanguinity variables over its 21 Municipalities have been investigated. Rates of consanguineous marriages and mean inbreeding levels recorded in some of the southern villages can be considered high but, average values for the entire region were lowered due to the early industrialization of the province. In spite of that, consanguinity in the study area has been, for a long time, a prevailing and conspicuous phenomenon when compared to the other Guipúzcoa regions. The impact of marriages between first cousins from immigrant groups on the regional inbreeding levels represents an interesting result as well. Geographic and demographic factors seem to be related both to the extent of marriages as well as to the number of potential mates within populations, which, in turn, are associated with mean inbreeding levels. Altitude seems to show weak relationship with population distribution and population consanguinity variables. Nevertheless, levels of endogamy appear positively correlated with consanguinity rates and mean inbreeding coefficient and, inversely related-but not statistically significant- to mean village sizes. First cousin marriages yield the highest levels of exogamy and exogamous M22 marriages were mostly concentrated within short (1–10 km) and long-range marital distances (>50 km). The aveaage values of Goierri have been compared with a consanguinity data set of some selected Spanish mountain populations taken from the literature. One of the main results is that geographic and demographic variables are poorly correlated with the most important inbreeding parameters. However, different clusters of populations can be observed with specific characteristics for each of them, not highly correlated with geography.     

Experimental infection magnifies inbreeding depression in house mice

It is often assumed that inbreeding reduces resistance to pathogens, yet there are few experimental tests of this idea in vertebrates, and no tests for the effects of moderate levels of inbreeding more commonly found in nature. We mated wild-derived mice with siblings or first cousins and compared the resistance of their offspring to Salmonella infection with outbred controls under laboratory and seminatural conditions. In the laboratory, full-sib inbreeding reduced resistance to Salmonella and survivorship, whereas first-cousin inbreeding had no detectable effects. In competitive population enclosures, we found that first-cousin inbreeding reduced male fitness by 57% in infected vs. only 34% in noninfected control populations. Our study provides experimental evidence that inbreeding reduces resistance and ability to survive pathogenic infection, and moreover, it shows that even moderate inbreeding can cause significant fitness declines under naturalistic conditions of social stress, and especially with exposure to infectious agents.     

Medicogenetic study of isolates in Uzbekistan. I. Statement of the problem and characteristics of the groups studied]

The paper comprises results of studying some demographic and populaton characteristics of the inhabitans of the Samarkand region as a whole and two villages, Karakent and Ishan, inhabited with Uzbeks-Khoja, a special religious-social caste in the past. It is shown that 87.4% of marriages in the Samarkand region are of international character (the information has been obtained on 7995 married couples). The frequency of consanguineous marriages is 11.6%, and among them 40.5% are first-cousin marriages and 39.1% are marriages of remote relatives. The coefficients of inbreeding are rather high among the Jewish, Tajik and Uzbek communities. The coefficient of inbreeding as a whole is F=0.0042 in this region and approaches to the maximal level, characterizing a panmix population. The average size of a family in the villages of Karakent and Ishan is approximately 4.0 persons. The values of reproductive performance, the nature of termination of pregnancies do not differ from those of panmix population. The percentage of intravillage and consanguineous marriages are 56% and 12.5% for the first village, and 25% and 2% for the second one respectively. The coefficient of inbreeding for karakent is F=0.0064, for Ishan--F=0.0014. Taking into consideration the historical development of the two villages and the cumulative data, the conclusion is drawn that Karakent is an isolate on a religious ground whereas Ishan is a disintegrated isolate.     

Estimating the risks for offspring of first-cousin matings. An approach.

Effects of parental consanguinity on morbidity and mortality can be estimated from observations on families ascertained through a child with a disease or defect, provided that appropriate corrections are made for the ascertainment bias. The risk of first-cousin parents having a child with a recessively inherited disease appears to be low (less than 1%). Data obtained by this approach suggest that the increased infant mortality associated with inbreeding (upon which calculations of lethal equivalents are based) may result in part from environmental differences between consanguineous and nonconsanguineous matings, which may be changing. Thus estimates of the number of lethal equivalents in a population can change as the environment changes.     

Consanguinity and susceptibility to infectious diseases in humans

Studies of animal populations suggest that low genetic heterozygosity is an important risk factor for infection by a diverse range of pathogens, but relatively little research has looked to see whether similar patterns exist in humans. We have used microsatellite genome screen data for tuberculosis (TB), hepatitis and leprosy to test the hypothesis that inbreeding depression increases risk of infection. Our results indicate that inbred individuals are more common among our infected cases for TB and hepatitis, but only in populations where consanguineous marriages are common. No effect was found either for leprosy, which is thought to be oligogenic, or for hepatitis in Italy where consanguineous marriages are rare. Our results suggest that consanguinity is an important risk factor in susceptibility to infectious diseases in humans.     

Screening for obesity in the offspring of first-cousin consanguineous couples: A Phase-I study in Saudi Arabia

Consanguineous or cousin marriages are very common in Saudi Arabia. However, owing to limited studies and insufficient knowledge about genetic diseases/disorders, many couples are unaware of the increased health risks for their offspring. Among the inherited and complex diseases from parents’ consanguinity, obesity is common; therefore, we examined the prevalence of obesity in the offspring of first-cousin consanguineous couples in Saudi Arabia. In this questionnaire-based study, 657 individuals (mean age = 18.7 ± 10.2 years; age range = 2–65 years) who were residing in Riyadh, Saudi Arabia participated. Among them, almost 90% were native Saudis. Participants mean body mass index (BMI) was 24.5 ± 9.1 kg/m2. Sex- stratified demographic details confirmed a significant association between age and BMI (p < .001). We confirmed that adolescents and adults were more prone to develop obesity. Adults and non-Saudi participants were three times more likely to develop obesity if they had first-cousin consanguineous parents than those who did not. Of the 30% of participants who were obese, 100 will be selected for Phase II, in which we plan to perform exome sequencing.     

Inbreeding in Gredos mountain range (Spain): contribution of multiple consanguinity and intervalley variation.

The present paper examines consanguineous marriages occurring between 1874 and 1975 in three valleys (Tormes, Alberche, and Tiétar) in the Sierra de Gredos mountain range, Avila province, Spain. Information was obtained from parish registers of 42 localities, corresponding to a total of 41,696 weddings. Consanguineous marriages were defined as those up to the third degree of consanguinity (second cousins). From 1874 to 1975 the percentage of related mates was 4.45% and the inbreeding coefficient was 0.0011868 (for 1874 to 1917 corresponding figures up to the fourth degree were 16.44% and 0.00 19085, respectively). In order to ascertain the characteristics and evolution of mating patterns in Gredos, the contribution of each degree of kinship was analyzed as a whole and then for each valley separately. Regarding total consanguineous marriages in Gredos, there is a low frequency of uncle-niece matings (0.21%) and a first-second cousin mating ratio (C22/C33) of 0.23 (up to the third degree of consanguinity). Before 1918 multiple matings (i.e., those involving more than a single relationship) accounted for 19.16% of consanguineous marriages (up to the fourth degree). The observed frequencies of multiple consanguineous marriages was, on average, about twice that expected at random, and the proportion of such marriages to total inbreeding was 34.65%. The temporal change of the Gredos inbreeding pattern was characterized by a recent decrease; the highest inbreeding levels correspond to the period from 1915 to 1944. Finally, intervalley differences (maximum inbreeding coefficient in the Tormes, minimum in the Tiétar) are interpreted considering the geography, population size, and population mobility for each valley     

Inbreeding pattern and reproductive success in a rural community from Galicia (Spain)

The present paper is based on information on marital patterns and reproductive performance (reconstituted families) in the rural community of Los Nogales, Galicia, Spain. Biodemographic data were used to analyse temporal changes and structure of consanguinity in the population, as well as consanguinity versus reproductive success. Of 2347 marriages celebrated between 1871 and 1977, 5.15% were between relatives (up to third degree). The population's inbreeding coefficient was above the Spanish average after 1890, and levels were high during the first part of the 20th century. A possible underestimation of inbreeding coefficients is attributed to the elevated frequency of extramarital births occurring in the Los Nogales population (13.47%). The structures of consanguineous matings, expressed as C22/C33 and C33/C44, turned out to be 0.86 and 0.82 respectively. Regarding migration, before 1920 consanguinity increased, but net migration was negative. In the period 1920-1929 consanguinity began to decrease, prior to maximum emigration. As for reproductive success, information from 1503 reconstituted families shows that complete fertility was slightly higher among consanguineous families despite a greater infant mortality. Lower infertility in consanguineous matings, as well as lower age at marriage and first maternity, could explain the above results.     

Consanguineous marriage in a newly developed country: the Qatari population

This study examines the frequency of consanguineous marriage and coefficient of inbreeding in the State of Qatar. The study was conducted in semi-urban areas of Doha between January and May 2004. A sample of 1515 married Qatari females aged 15 years and over participated. The degree of consanguinity between each female and her spouse, and degree of consanguinity between their parents were recorded. The rate of consanguinity in the present generation was high (54.0%) with a coefficient of inbreeding of 0.02706. The commonest type of consanguineous marriage was between first cousins (34.8%). Double first cousin marriages were common (3.1%) compared with other populations. The consanguinity rate in the State of Qatar has increased from 41.8% to 54.5% in one generation.     

Effects of polygyny and consanguinity on high fertility in the rural Arab population in South Jordan

Based on the authors' interview survey for 608 randomly selected women of the rural Arab population in the South Ghor district of Jordan, this paper examined the effects of polygyny and consanguinity on high fertility, which was recognized as natural fertility. The prevalence of polygynous and consanguineous marriages was 28.0% and 58.1%, respectively, largely reflecting the population's traditional marriage customs. The findings highlighted a significantly higher total marital fertility rate (TMFR) in the monogamous wives (10.5) than in the senior polygynous (8.1) and junior polygynous wives (8.6); the TMFR did not significantly differ among the wives of non-consanguineous, first-cousin and second-cousin marriages. The formation of polygynous marriage was decided by the husband, mostly as a result of his senior wife's infecundity or sub-fecundity, and the age of the husband at marriage to his junior polygynous wife was high in many cases, leading to a decline in this wife's fecundity.     

Apparent inbreeding preference despite inbreeding depression in the American crow

Although matings between relatives can have negative effects on offspring fitness, apparent inbreeding preference has been reported in a growing number of systems, including those with documented inbreeding depression. Here, we examined evidence for inbreeding depression and inbreeding preference in two populations (Clinton, New York, and Davis, California, USA) of the cooperatively breeding American crow (Corvus brachyrhynchos). We then compared observed inbreeding strategies with theoretical expectations for optimal, adaptive levels of inbreeding, given the inclusive fitness benefits and population‐specific magnitude of inbreeding depression. We found that low heterozygosity at a panel of 33 microsatellite markers was associated with low survival probability (fledging success) and low white blood cell counts among offspring in both populations. Despite these costs, our data were more consistent with inbreeding preference than avoidance: The observed heterozygosity among 396 sampled crow offspring was significantly lower than expected if local adults were mating by random chance. This pattern was consistent across a range of spatial scales in both populations. Adaptive levels of inbreeding, given the magnitude of inbreeding depression, were predicted to be very low in the California population, whereas complete disassortative mating was predicted in the New York population. Sexual conflict might have contributed to the apparent absence of inbreeding avoidance in crows. These data add to an increasing number of examples of an “inbreeding paradox,” where inbreeding appears to be preferred despite inbreeding depression.     

Variation in inbreeding depression among populations of the seed beetle, Stator limbatus

Inbreeding depression has been documented in many insect species, but the degree to which it varies among traits within populations and among populations within species is poorly understood. We used a single‐generation factorial breeding design to examine variation in inbreeding depression among three populations of the seed‐feeding beetle, Stator limbatus Horn (Coleoptera: Chrysomelidae: Bruchinae), from the southwestern USA. Eggs from sib matings were less likely to develop and hatch, and larval hatch‐to‐adult mortality was higher for offspring of sib matings. Overall, inbreeding resulted in a reduction in the proportion of eggs that produced an adult from >80% for outbred matings in all three populations to an average of only 54% for inbred matings. Of those larvae that survived to adult, inbred beetles took ～1.5 days (>5%) longer to reach adult. The only measured trait not affected by inbreeding was adult body mass. The degree to which inbreeding increased mortality varied among the populations – inbreeding depression was lowest in the population that is most isolated. Although populations of S. limbatus are generally large in nature our results suggest that increased inbreeding associated with population fragmentation can have substantial effects on fitness of S. limbatus.     

Incidence in Italy, genetic heterogeneity, and segregation analysis of cystic fibrosis

Taking advantage of the availability of an archive of consanguineous marriages that gives accurate estimates of consanguinity in Italy, it has been possible to calculate the increase of first- and second-cousin marriages among 624 couples of cystic fibrosis (CF) parents over the general population. From these estimates, the incidence of CF in Italy has been found to correspond approximately to 1/2,000. In turn, the same data have been used to test the hypothesis of genetic heterogeneity of CF, recently proposed, which is based on the presence of two distinct genetic disorders having similar frequencies. If such a hypothesis were true, the number of first-cousin marriages among CF parents should be significantly higher than that observed in our present study. Finally, the segregation analysis of 624 CF sibships has yielded under multiple selection a segregation ratio of 0.252, confirming the recessive mode of inheritance.