Introduction
A consanguineous marriage is defined as a union between biologically related persons. This type of marriage is common in many Asian and African populations (Saha & El Sheikh, Reference Saha and El Sheikh1988; Tuncbilek & Koc, Reference Tuncbilek and Koc1994; Bittles, Reference Bittles2001; Alper et al., Reference Alper, Erengin, Manguoglu, Bilgen, Cetin, Dedeoglu and Luleci2004; COSIT, 2006; Othman & Saadat, Reference Othman and Saadat2009; Shawky et al., Reference Shawky, El-Awady, Elsayedm and Hamadanm2011; El-Kheshen & Saadat, Reference El-Kheshen and Saadat2013). Iranian populations show high levels of consanguineous marriages (Saadat et al., Reference Saadat, Ansari-Lari and Farhud2004; Rafiee & Saadat, Reference Rafiee and Saadat2011). Consanguinity is a long-standing social habit (Bittles, Reference Bittles2001; Saadat, Reference Saadat2007, Reference Saadat2008b) and its frequency is associated with several demographic, religious, cultural and socioeconomic factors (Bittles, Reference Bittles2001; Hamamy et al., Reference Hamamy, Jamhawi, Al-Darawsheh and Ajlouni2005; Akrami & Osati, Reference Akrami and Osati2007; Saadat, Reference Saadat2007).
Considering that consanguinity results in homozygosity in offspring, it is associated with an elevation in the risk of autosomal recessive disease and several multifactorial complex traits (Bittles & Neel, Reference Bittles and Neel1994; Stoltenberg et al., Reference Stoltenberg, Magnus, Skrondal and Lie1999; Bittles, Reference Bittles2001; Saadat & Zendeh-Boodi, Reference Saadat and Zendeh-Boodi2006; Saadat, Reference Saadat2008a; Tadmouri et al., Reference Tadmouri, Nair, Obeid, Al Ali, Al Khaja and Hamamy2009; Mansour et al., Reference Mansour, Fathi, Klei, Wood, Chowdari and Watson2010; Saadat & Vakili-Ghartavol, Reference Saadat and Vakili-Ghartavol2010; Nafissi et al., Reference Nafissi, Ansari-Lari and Saadat2010, Reference Nafissi, Ansari-Lari and Saadat2011; Anvar et al., Reference Anvar, Namavar-Jahromi and Saadat2011; Saadat, Reference Saadat2011, Reference Saadat2015a).
Previous studies have shown that Iranian people are a heterogeneous population (Amirshahi et al., Reference Amirshahi, Sunderland, Farhud, Tavakoli, Daneshmand and Papiha1992; Rafiee et al., Reference Rafiee, Saadat and Saadat2010; Fallahzadeh-Abarghooei et al., Reference Fallahzadeh-Abarghooei, Zahedi, Mirabedi and Saadat2015; Saadat, Reference Saadat2015b). The Mandaean community is one of the Iranian sub-populations. Mandaeans are a closed ethno-religious community, practising Mandaeism, which is a Gnostic religion (Aramaic manda means ‘knowledge’, as does the Greek gnosis). Mandaeism has a strongly dualistic worldview. The connection with the Quranic Sabians provided them with acknowledgment as People of the Book – a legal minority religion within the Muslim community. According to most scholars, Mandaeans migrated from Jordan/Palestine areas to southern Iraq and south-west Iran areas about 2000 years ago. They are Semites and speak a dialect of Eastern Aramaic known as Mandaic. Aramaic is a language family belonging to the Semitic subfamily of the Afroasiatic language family (Buckley, Reference Buckley2002).
The patterns of consanguinity among several Iranian populations have been reported previously (Saadat et al., Reference Saadat, Ansari-Lari and Farhud2004; Rafiee & Saadat, Reference Rafiee and Saadat2011). To the authors’ knowledge, there are no data for prevalence of consanguineous marriages among Iranian and Iraqis Mandaeans. Therefore, the present study was carried out in Khuzestan Province.
Methods
Subjects
This cross-sectional study was carried out in Khuzestan Province in south-west Iran in 2016. A total of 137 Mandaean couples (urban areas: 79 couples; rural areas: 58 couples) were included in the study. No other ethnic/religious groups were included. Data on consanguineous marriages were collected using a simple questionnaire by interview. The questionnaires were completed by a trained interviewer. The work has been carried out in accordance with the Code of Ethics of the World Medical Association (Declaration of Helsinki) for studies in humans. Informed consent was obtained from all participants.
Consanguineous marriages
The coefficient of inbreeding (F) is the probability that an individual has received both alleles of a pair from an identical ancestral allele. Marriages were classified by the degree of biological relationship between couples as double first cousins (F=1/8), first cousins (F=1/16), first cousin once removed (F=1/32), second cousins (F=1/64) and unrelated marriages (F=0). The average coefficient of inbreeding (α) was calculated as F=∑P i F i , where P i and F i are the frequency and coefficient of inbreeding of each mating type, respectively.
First cousins may be the children of two brothers (patrilateral parallel cousins), two sisters (matrilateral parallel cousins) or a brother and a sister (cross-cousins).
Statistical analysis
The chi-squared test (χ 2) was used to compare mating pattern frequencies between study groups. Statistical analysis was performed using the statistical software package SPSS (SPSS Inc., Chicago, IL, USA; Version 11.5). A probability of p<0.05 was considered statistically significant.
Results and Discussion
Table 1 shows the frequency of the various types of marriages in urban and rural areas. The data showed that the overall frequency of consanguinity was 50.7% in urban and 86.2% in rural areas. The equivalent mean inbreeding coefficient (α) was 0.0272 and 0.0487 in urban and rural areas, respectively. There was a significant difference between rural and urban areas for the types of marriages (χ 2=24.8, df=4, p<0.001). This means that consanguinity was higher in rural areas compared with urban areas. A similar finding has been reported by other investigators in Algeria (Benallegue & Kedji, Reference Benallegue and Kedji1984), Jordan (Khoury & Massad, Reference Khoury and Massad1992), Iraq (COSIT, 2006), Turkey (Alper et al., Reference Alper, Erengin, Manguoglu, Bilgen, Cetin, Dedeoglu and Luleci2004), Egypt (Hafez et al., Reference Hafez, El-Tahan, Awadalla, El-Khayat, Abdel-Gafar and Ghoneim1983), Syria (Othman & Saadat, Reference Othman and Saadat2009) and Afghanistan (Saify & Saadat, Reference Saify and Saadat2012; Saadat & Tajbakhsh, Reference Saadat and Tajbakhsh2013).
Frequency distribution of different types of consanguineous marriages in Iranian Mandaeans, Khuzestan Province, 2016
First cousin marriages (51.8%) were the most common type of marriages and the α-value was estimated to be 0.0363 for the Iranian Mandaean population. The rates of first cousin marriages were 35.4% and 74.1% in urban and rural areas, respectively.
It should be noted that among several west Asian countries, the most common form of consanguineous marriage is between first cousins (Hafez et al., Reference Hafez, El-Tahan, Awadalla, El-Khayat, Abdel-Gafar and Ghoneim1983; Tuncbilek & Koc, Reference Tuncbilek and Koc1994; Alper et al., Reference Alper, Erengin, Manguoglu, Bilgen, Cetin, Dedeoglu and Luleci2004; Hamamy et al., Reference Hamamy, Jamhawi, Al-Darawsheh and Ajlouni2005; Othman & Saadat, Reference Othman and Saadat2009; Rafiee & Saadat, Reference Rafiee and Saadat2011; El-Kheshen & Saadat, Reference El-Kheshen and Saadat2013). Among Iranian populations, first cousin marriages account for about 28% of all marriages (Saadat et al., Reference Saadat, Ansari-Lari and Farhud2004), which is similar to the findings of other reports from Arabic countries (Hafez et al., Reference Hafez, El-Tahan, Awadalla, El-Khayat, Abdel-Gafar and Ghoneim1983; Benallegue & Kedji, Reference Benallegue and Kedji1984; Khoury & Massad, Reference Khoury and Massad1992; Othman & Saadat, Reference Othman and Saadat2009; Shawky et al., Reference Shawky, El-Awady, Elsayedm and Hamadanm2011; El-Kheshen & Saadat, Reference El-Kheshen and Saadat2013). The present finding might be at least in part interpreted by the fact that Mandaeans originated in the west of Asia (Buckley, Reference Buckley2002), and that consanguinity was deeply rooted in the populations living in these areas (Bittles, Reference Bittles2001; Saadat, Reference Saadat2007, Reference Saadat2008b).
Patrilateral parallel cousin marriages were the most common type of consanguineous marriages among Mandaeans (data not shown). It should be noted that it is a similar story in Iran (Saadat et al., Reference Saadat, Ansari-Lari and Farhud2004), Syria (Othman & Saadat, Reference Othman and Saadat2009), Lebanon (El-Kheshen & Saadat, Reference El-Kheshen and Saadat2013) and several other populations in Asia (Saify & Saadat, Reference Saify and Saadat2012; Saadat & Tajbakhsh, Reference Saadat and Tajbakhsh2013).
The prevalence of consanguinity among the Arab population living in Iran has previously been reported to be 49.0% (Saadat et al., Reference Saadat, Ansari-Lari and Farhud2004). Although Mandaeans and Arabs are Semites, there a significant difference was found between these populations regarding consanguineous marriages (χ 2=303.3, df=4, p<0.001). Mandaeans showed a higher level of consanguinity compared with Iranian Arabs mainly living in Khuzestan Province. This point confirms that consanguineous marriages are a very important factor in maintaining social stability (Tadmouri et al., Reference Tadmouri, Nair, Obeid, Al Ali, Al Khaja and Hamamy2009). Therefore, it might be concluded that, at least in part, Mandaeans selected a high level of consanguineous marriages to keep their ethno-religious community.
On the other hand, it has been shown that attitude and subsequently practice towards consanguineous marriages is strongly correlated with the historical background of populations (Saadat, Reference Saadat2007, Reference Saadat2008b). Iranian Mandaeans originated from the west of Asia (Buckley, Reference Buckley2002), where at the present time consanguinity is high in these populations. It seems that a high level of marriages with relatives was a feature of west Asian populations.
It should be mentioned that the small sample size was a major limitation of this study. The study demonstrated a very high level of consanguineous marriage among Iranian Mandaeans. It has been shown that consanguinity significantly increases the prevalence of inherited autosomal recessive diseases and many multifactorial traits such as infertility, congenital disorders, and mental retardation (Bittles et al., Reference Bittles, Grant and Shami1993; Bittles & Neel, Reference Bittles and Neel1994; Stoltenberg et al., Reference Stoltenberg, Magnus, Skrondal and Lie1999; Bittles, Reference Bittles2001; Saadat & Zendeh-Boodi, Reference Saadat and Zendeh-Boodi2006; Saadat, Reference Saadat2008a; Tadmouri et al., Reference Tadmouri, Nair, Obeid, Al Ali, Al Khaja and Hamamy2009; Mansour et al., Reference Mansour, Fathi, Klei, Wood, Chowdari and Watson2010; Saadat & Vakili-Ghartavol, Reference Saadat and Vakili-Ghartavol2010; Nafissi et al., Reference Nafissi, Ansari-Lari and Saadat2010, Reference Nafissi, Ansari-Lari and Saadat2011; Anvar et al., Reference Anvar, Namavar-Jahromi and Saadat2011; Saadat, Reference Saadat2011, Reference Saadat2015a). The harmful consequences of consanguineous mating emphasize the need for genetic counselling in the Mandaean community and the importance of preventive action to raise awareness about the risks of consanguinity.
Acknowledgments
The authors are indebted to the study participants for their close co-operation. They also thank Mr Salam Choheili (Great Leader of the Iranian Mandaean) for his support. They are also grateful to Dr Maryam Ansari-Lari for her contribution in revising and editing the manuscript. The study was supported by Shiraz University, Iran (94GRD1M1741). The authors have no conflicts of interest to declare.
