Consanguinity in the Archbishopric of Toledo, Spain, 1900-79. I. Types of consanguineous mating in relation to premarital migration and its effects on inbreeding levels

This study, the first of a series on consanguinity in the Archbishopric of Toledo from 1900 to 1979, analyses in detail the types of consanguineous mating in a population of considerable size, some 650,000 persons, in Central Spain. During the period covered, very important transformations occurred in Spanish society. The data relate to 21,464 consanguineous marriages. They were divided into two groups, according to the premarital migration of the couple. Significant differences in the frequencies of the types of consanguineous matings, and their secular evolution, are found for the two groups. The expected trend in inbreeding in the total area shows two different tendencies: constancy till the end of the 1950s, followed by a fast decline during the last two decades.     

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.     

Socioeconomic, demographic and legal influences on consanguinity and kinship in northern coastal Sweden 1780-1899

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 Skellefte? 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.     

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 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     

Influence of educational levels of the spouses on consanguinity among three endogamous groups of Andhra Pradesh,South India

The highest values of consanguinity was found among “Kamma” (45.0%), “Ediga” (47.5%) and “Mala” (55.7%) who occupy different strata of Indian caste hierarchy. In the way of searchout the factors influencing consanguineous marriages, the present paper finda the negative relationship between educational levels of the spouses and consanguinity. The educational levels of men has significant effect on the frequency of consanguinious marriages among “Kamma” and “Mala”. However, further analysis deplore significant differences in the mean levels consanguinity between educational groups. It divulge low level of higher education among the populations. Only 12% of men and 1.6% of women have degree level and above education in the total sample.     

The practice of consanguineous marriage in oman: prevalence, trends and determinants

The practice of consanguineous marriage has been the culturally preferred form of marriage in most Arab and the Middle Eastern countries, including Oman, but due to a paucity of population-based data in the past there is a dearth of information about its form and dynamics in Oman. Recent national-level surveys allow this gap to be filled. This paper examines the prevalence, trends and determinants of consanguineous marriages in Oman using data from the 2000 Oman National Health Survey. The results indicate a very high prevalence of consanguineous marriage in Oman, as more than half (52%) of marriages are consanguineous. First cousin unions are the most common type of consanguineous unions, constituting 39% of all marriages and 75% of all consanguineous marriages. The study observed various patterns of consanguinity, some of them common with other Arab nations, and some unique in nature. Women's age at marriage, employment, place of childhood residence and geographical region appear to be significant determinants of consanguineous marriages. Consanguineous marriage shows a strong association with marital stability, early age at marriage and early-age childbearing. There has been no appreciable change in the prevalence of consanguineous unions in Oman over the last four decades despite massive socioeconomic development and modernization. However, recent marriage cohorts show slight declining trends. The results suggest that consanguinity is likely to remain stable in the future or decline at a slow rate. Specific health education and genetic counselling should be followed in line with WHO recommendations to minimize the negative health consequences of consanguinity for child health.     

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).     

Consanguinity and congenital heart disease in the rural Arab population in northern Israel

The incidence of congenital heart disease (CHD) was examined in relation to the consanguinity of the parents. The study was performed in five Arab villages in the Western Galilee, Israel, where consanguineous matings are known to be very high. All children up to the age of 7 years were included in this study; there were 1,546 children, 32% were the offspring of consanguineous marriages including first- and second-degree cousins. A higher percentage of isolated CHD was found in the offspring of consanguineous marriages: 2.81% out of 498 children compared to 1.24% in 1,048 offspring of unrelated parents. Among 373 children whose parents were first cousins the percentage of CHD rose to 3.22. The differences in CHD frequencies were found to be statistically significant. CHD is believed to have a multifactorial background. This study shows that the genetic influence is an important factor in the etiology of such malformations.     

Prevalence and sociodemographic correlates of consanguineous marriages in Turkey

The aim of this study was to determine the prevalence and sociodemographic correlates of consanguineous marriages in Turkey using data derived from the 2003 Turkey Demographic and Health Survey (TDHS-2003). Demographic surveys conducted in the last 40 years consistently show that Turkey is a country with a high level of consanguinity. In the latest demographic survey (TDHS-2003), a nationally representative sample of 8075 ever-married women, consanguineous marriages accounted for 22% of the total, which is equivalent to a mean coefficient of inbreeding (alpha) of 0.011. There are changing secular profiles in the rates of consanguinity in general and of the specific sub-types of cousin marriages in particular in Turkey. The prevalence of first cousin marriages among all consanguineous marriages presents a steady decline from one marriage cohort to the next. The changes observed over time may be attributable to several factors such as the increase in educational level of women, the nuclearization of the family system, the mobility from rural to urban settings, a better socioeconomic status of families, an increase in women's labour force participation in formal sectors, lower fertility rates resulting in a smaller number of cousins available for marriage, and an increased awareness of the effects of consanguineous unions on child health in cases where there is an inherited recessive disease in the family. Any attempts to discourage consanguinity at the population level appear to be inappropriate and undesirable, especially when the consanguineous union remains an integral part of the cultural and social life of Turkey. Nevertheless the WHO-recommended approach to minimizing the negative effects of consanguinity on child health should be followed, i.e. the identification of families with a high risk of a genetic disease and the provision of prospective genetic counselling.     

Evolution of marital structure in 20 Sardinian villages from 1800 to 1974

This paper reports the data for endogamy, exogamy and consanguinity in 20 Sardinian villages from 1800 to 1974, divided into generational periods (25 years). The data are taken from the records of 48,262 marriages celebrated in the parishes of 20 Sardinian villages. The results for Spearman's rank correlation coefficient indicate significant positive correlations of endogamy with consanguinity (r(s) = 0.6551, percentage of consanguineous marriages; r(s) = 0.5477, Bernstein's alpha), with altitude (r(s) = 0.6386), with population size (r(s) = 0.2519), as well as a significant negative correlation of endogamy with time (r(s) = -0.4210). In addition, consanguinity shows a significant positive correlation with altitude (r(s) = 0.5717, percentage of consanguineous marriages; r(s) = 0.6295, Bernstein's alpha) and a significant negative correlation with time (r(s) = -0.2363, percentage of consanguineous marriages); the negative correlation between the mean level of consanguinity (alpha) and time is statistically not significant. In the single parishes, the levels of endogamy and consanguinity are generally higher in the mountain villages than in those situated in the hill and plain areas. Finally, it is hypothesized that, in the time period considered, the level of consanguinity and especially of endogamy were largely determined by isolation.     

Inbreeding effects on fetal growth in Beirut, Lebanon

Effects of consanguineous marriages on offspring's gestational age and anthropometrics at birth were investigated in Beirut through a hospital-based survey of 1,252 newborns. Twenty-five percent of all newborns were inbred, and the mean inbreeding coefficient was 1.25%. Neither prematurity rate nor weight, length, head circumference, and chest circumference (considered individually, or as a whole) showed a significant pattern by type of parental consanguinity. Failure to demonstrate significant inbreeding effects is reported in several other studies and generally interpreted as the long-term result of continued inbreeding practices.     

Consanguineous marriages in the province of Antalya, Turkey

To assess the trends in the frequency and the medical effects of consanguinity in the south coast of Turkish population using local and national data in the last 11 years. This cross-sectional study was carried out in Manavgat province, which is a major tourism center on the Mediterranean coast of Turkey. The authors studied consanguineous marriages in rural and urban population in the Mediterranean coast, Manavgat province, Turkey, via a 1500 random survey sample of married couples. There has been a significant increase in the incidence of consanguineous marriages in rural areas (40.7%) since 1989 in the southern population of Turkey. The results showed that the most frequent type of marriage was between the first cousins. It is found that there is no statistically significant difference between the consanguineous and non-consanguineous marriages in the different age groups. The results were discussed on the basis of educational status, reasons for having consanguineous marriages and the general medical effects as well as with the relation of congenital malformations. The custom of consanguineous unions in the Mediterranean population of Turkey is still extremely high, and preventive measures should be done to decrease its frequency and associated complications.     

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.     

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.     

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.     

Socioeconomic, demographic, and geographic variables affecting the diverse degrees of consanguineous marriages in Spain

In a population the inbreeding coefficient alpha is determined by the relative incidence of the various degrees of consanguineous marriages--uncle-niece or aunt-nephew (C12), first cousin (C22), first cousin once removed (C23), second cousin (C33)--which may be related to temporal, geographic, demographic, and economic factors. Using published information from Spain corresponding to urban and rural areas, in this article we seek to establish how each specific relationship behaves with respect to geographic, demographic, and socioeconomic factors, to determine differential urban-rural patterns, and to study whether the diverse types of consanguineous matings relate homogeneously to these factors. For this purpose we performed multiple regressions in which the dependent variables were the different degrees of consanguinity previously selected and the independent variables were geographic, demographic, and economic factors. Our results indicate that the various types of consanguineous marriages in Spain are more conditioned by geographic, demographic, and economic variables than by the inbreeding level alpha (the coefficient of determination was between 0.22 and 0.72; the maximum for alpha was 0.35). A regional pattern exists in Spain and corresponds to close and to remote kinship, which may be mainly related to economic and family factors. Close relationships appear to be more associated with economic variables, whereas second-cousin marriages correspond largely to rural areas of the Spanish Central Plateau.     

Incidence of Friedreich ataxia in Italy estimated from consanguineous marriages

The frequency of consanguineous marriages up to second-cousin degree has been carefully established in the past for each of the 95 Italian provinces using the Archive of about 500,000 dispensations given by the Catholic church for such marriages over a 55-year period. It has therefore been possible to compare the frequency of consanguineous marriages observed among 83 couples of parents of Friedreich patients with the frequency of consanguineous marriages of the same degree in the different Italian provinces during the same years. From these data, an estimate of the incidence of the disease has been obtained for the whole nation (between 1/22,000 and 1/25,000). In Southern Italy, where 16 out of the 18 consanguineous marriages among Friedreich parents are concentrated, the incidence of the disease is similar (between 1/25,000 and 1/28,000). This study indicates that the Archive of consanguinity existing in Italy allows a reliable comparison of the frequency of consanguineous marriages among parents of patients with that of the general population. The same method can therefore be applied to the study of incidence of other autosomal recessive disorders in Italy.     

Trends of consanguineous marriages in a Sunni Muslim population of West Bengal, India

The Muslim population of the Chaltaberia village in the district of South 24 Parganas in West Bengal is divided into several wards (paras) inhabited by people of specific surnames. The frequency of endogamous marriages within surnames is greater than randomly expected ones. An incomplete reproductive isolation is observed among the five dominant surnames. Consanguineous marriages occur more often outside the village than inside. Leaving out marriages between long distances, a small median distance of 6.36 km is recorded. The neighborhood area works up to be 552.2 km2, which is rather small. There is an underlying process of breeding isolation by distance. A generation length of 21 years has been used for examining the temporal change in consanguineous marriages and inbreeding, which generally appears to increase. There is a general trend of decline in consanguineous marriages towards the southern part of West Bengal and eastern part of Assam among the Bengalee Muslims. The frequency of consanguineous marriages is 7.3% out of all marriages (N=1153) that have taken place in six generations in the population. The first cousin marriage is nearly 50% of all marriages. Patrilineal marriages are common in marriages between second and third cousins. An increase of consanguineous marriages in the younger generation was observed, but the total frequency agrees with a general trend of a decline in the frequency of consanguineous marriages among the Muslims in this part of India.