Consanguinity is common in many countries, particularly in developing nations and the Muslim world [1, 2]. In countries such as Iran, Turkey, Saudi Arabia, and Pakistan, consanguineous unions are favored both socially and culturally. Consanguinity and inbreeding coefficient F (ICF) are of great interest because of their potential association with genetic anomalies and various health indicators. The prevalence of consanguinity has been shown to exhibit wide variation across geography and cultures, and correspondingly, the determinants of consanguinity vary in different populations [3, 4, 5]. The most common sociodemographic factors associated with high consanguinity are rural origin, low literacy, poor socioeconomic status, extended household, and cultural norms [1, 6, 7, 8].
The underlying reasons for high consanguinity in Pakistan are sociocultural, including longstanding cultural norms of parents and family elders playing a key role in marriage decision-making, a sense of family obligation and reciprocity, pride in staying within the
In Pakistan, most studies of consanguinity have focused on various population subgroups in the Punjab province [3, 10, 11], while there have been limited studies in other ethnic groups such as those in the Khyber Pakhtunkhwa (KPK) province (formerly known as North-West Frontier Province). Consanguinity has been reported from small and rather isolated populations of KPK, such as Swat [12], Sikhs in Peshawar [13], Malakand [14], Bajaur [4], and Dir Lower [9]. However, data on multiethnic and cosmopolitan populations of KPK are scarce. To address this scarcity of data, we have conducted a detailed study to assess the prevalence and correlates of consanguinity in the Mardan metropolis of KPK.
The study was undertaken in Mardan, the second largest district in the KPK province, both geographically and in population size. The population comprised various tribes of Pashtuns. The district is divided into 3
This study was approved by ethical review committees of the Hazara University, Mansehra (F. No. 185/HU/Zool/2014/2305 and 2015/3145) and Quaid-i-Azam University, Islamabad. A population-based study was conducted in the Mardan district from September 2014 to March 2015. A convenience sample of ever-married men was recruited from 3
sites: 13 from Mardan, 11 from Katlang, and 18 from Takht Bhai
Data were obtained on tehsil and rural or urban origin of the participants. Self-identified tribal affiliation was grouped into a primary Pashtun caste (
There were 7 types of marital unions, which were classified into 2 broad categories, i.e., consanguineous unions and noncon–sanguineous unions. Consanguineous unions comprised 4 types: marriages between double first cousins (DFCs), first cousins (FCs), first-cousin-once-removed (FCOR), and second cousins (SCs); while nonconsanguineous unions comprised 3 types: marriages between second-cousin-once-removed (SCOR), distantly related/
Data were analyzed using MS Excel and GraphPad Prism software (version 5). Standard summaries were generated; consanguineous unions and all marriages were cross-tabulated across the sociodemographic variables, and a chi-square contingency test was used to check the independence between the categorical variables [21]. ICF was estimated from the weighted proportion of individual consanguineous union types [1]. Bivariate logistic regression analyses were performed using STATA (version 11), and the results were expressed as unadjusted odd ratios (ORs). The dependent variable, i.e., consanguineous union, was taken as dichotomous, and the sociodemographic factors were coded as independent variables [22]. In each variable, the category with the lowest prevalence of consanguineous union was taken as the reference. For the multivariable regression analyses, a stepwise (likelihood ratio) logistic regression was performed. Only the significant variables were retained in the final model.
A total of 1,202 unrelated men were enrolled. The sample size ranged from 314 individuals from Mardan tehsil to 571 from Takht Bhai tehsil (
Distribution of major types of marital unions and ICF in 3
Tehsil | Consanguineous unions, n (%) | Nonconsanguineous unions, n (%) | |||||||
---|---|---|---|---|---|---|---|---|---|
DFC | FC | FCOR | SC | SCOR | DR | Unrelated | All marriages | ICF | |
Mardan | 8 (2.5) | 87 (27.7) | 13 (4.1) | 11 (3.5) | 2 (0.6) | 28 (8.9) | 165 (52.5) | 314 (26.1) | 0.0223 |
Katlang | 6 (1.9) | 100 (31.5) | 16 (5.0) | 12 (3.8) | 4 (1.3) | 45 (14.2) | 134 (42.3) | 317 (26.4) | 0.0243 |
Takht Bhai | 10 (1.8) | 223 (39.1) | 29 (5.1) | 15 (2.6) | 4 (0.7) | 69 (12.1) | 221 (38.7) | 571 (47.5) | 0.0286 |
ICF, inbreeding coefficient F; DFC, double first cousin; FC, first cousin; FCOR, first-cousin-once-removed; SC, second cousin; SCOR, second-cousin-once-removed; DR, distantly related/
The FC unions comprised 77.4% of the consanguineous marriages. Among these, FBD was the most prevalent type (35.4%), followed by FSD (27.6%), MBD (25%), and MSD types (12%) (
Distribution of types of FC unions in
Variable | FC marriage type (n) | n | % | |||
---|---|---|---|---|---|---|
FBD | FSD | MBD | MSD | |||
Mardan | 33 | 26 | 20 | 8 | 87 | 27.7 |
Katlang | 38 | 23 | 23 | 16 | 100 | 31.5 |
Takht Bhai | 74 | 64 | 60 | 25 | 223 | 39.1 |
Rural | 119 | 89 | 88 | 42 | 338 | 35.1 |
Urban | 26 | 24 | 15 | 7 | 72 | 30.0 |
#Distributions were statistically not significant
FC, first cousin; FBD, father’s brother’s daughter; FSD, father’s sister’s daughter; MBD, mother’s brother’s daughter; MSD, mother’s sister’s daughter
In the tehsil-wise samples, the highest consanguinity was observed in Takht Bhai (48.5%), followed by Katlang (42.3%) and Mardan (37.9%) (
Consanguinity tends to be higher among literate individuals (45.7%) than among those who were illiterate (39.4%); however, the difference was not quite significant (
Four 5-year intervals for the year of marriage were defined (
Distribution of consanguineous unions, all marriages, and ICF in demographic variables of Mardan population
Variable | Consanguineous unions | All marriages | Univariate logistic regression OR | 95% CI | ||
---|---|---|---|---|---|---|
n | % | n | % | |||
Mardan | 119 | 37.9 | 314 | 26.1 | Ref. | – |
Katlang | 134 | 42.3 | 317 | 26.4 | 1.20 | 0.872–1.650 |
Takht Bhai* | 277 | 48.5 | 571 | 47.5 | 1.54 | 1.166–2.045 |
Rural | 430 | 44.7 | 962 | 80.0 | 1.13 | 0.849–1.507 |
Urban | 100 | 41.7 | 240 | 20.0 | Ref. | – |
Illiterate | 121 | 39.4 | 307 | 25.5 | Ref. | – |
Literate | 409 | 45.7 | 895 | 74.5 | 1.29 | 0.993–1.684 |
Up to 8 | 40 | 50.6 | 79 | 6.57 | 1.36 | 0.836–2.216 |
9–12 | 213 | 47.0 | 453 | 37.7 | 1.18 | 0.892–1.555 |
13 and higher | 156 | 43.0 | 363 | 30.2 | Ref. | – |
1985 or earlier | 57 | 47.5 | 120 | 9.98 | Ref. | – |
1986–1995* | 116 | 40.0 | 290 | 24.1 | 0.74 | 0.480–1.131 |
1996–2005* | 215 | 46.0 | 467 | 38.9 | 0.94 | 0.631–1.409 |
2006–2015* | 142 | 43.7 | 325 | 27.0 | 0.86 | 0.563–1.305 |
Up to 30* | 117 | 47.8 | 245 | 20.4 | 1.47 | 0.966–2.246 |
30.1–40* | 223 | 45.1 | 494 | 41.1 | 1.33 | 0.904–1.944 |
40.1–50 | 136 | 42.2 | 322 | 26.8 | 1.18 | 0.786–1.767 |
350 | 54 | 38.3 | 141 | 11.7 | Ref. | – |
#Distribution of consanguineous unions was statistically significant in the chi-square test statistics
*Significant in regression analyses
ICF, inbreeding coefficient F; OR, odd ratio; 95% CI, 95% confidence interval; Ref., reference
Among the 20 Pashtun subcastes represented by recruited participants, there were 11 major tribe systems. Marked heterogeneity in consanguinity was evident among the tribes. The highest prevalence of consanguinity was observed in Pela Khel (59.7%; OR = 6.66; 95% CI: 2.06–11.65), followed by Afghan
(49.2%; OR = 5.1; 95% CI: 2.66–16.69) and Khattak (46.5%; OR = 3.92; 95% CI: 1.74–10.88;
Distribution of consanguineous unions, all marriages, and ICF in socioeconomic variables of Mardan population
Variable | Consanguineous unions | All marriages | Univariate logistic regression OR | 95% CI | ||
---|---|---|---|---|---|---|
n | % | n | % | |||
Professionals | 200 | 46.2 | 433 | 36.0 | 1.25 | 0.939–1.654 |
Agriculture/farming | 146 | 40.8 | 358 | 29.8 | Ref. | – |
Unskilled manual | 75 | 45.2 | 166 | 13.8 | 1.20 | 0.826–1.735 |
Sales/business | 44 | 42.3 | 104 | 8.7 | 1.06 | 0.684–1.657 |
Skilled manual | 19 | 42.2 | 45 | 3.7 | 1.06 | 0.566–1.988 |
Services | 19 | 42.2 | 45 | 3.7 | 1.06 | 0.566–1.988 |
Others (n < 27) | 27 | 52.9 | 51 | 4.2 | 1.63 | 0.907–2.944 |
Up to 5 | 121 | 42.2 | 287 | 23.9 | Ref. | – |
>5–10 | 82 | 45.6 | 180 | 15.0 | 1.15 | 0.789–1.671 |
>10–20 | 155 | 44.7 | 347 | 28.9 | 1.11 | 0.808–1.518 |
>20–40 | 142 | 47.8 | 297 | 24.7 | 1.26 | 0.907–1.742 |
>40 | 30 | 33.0 | 91 | 7.57 | 0.67 | 0.411–1.108 |
Makori | 8 | 18.2 | 44 | 3.7 | Ref. | – |
Dalazak | 12 | 30.8 | 39 | 3.2 | 2.00 | 0.718–5.571 |
Dewan Khel* | 16 | 34.8 | 46 | 3.8 | 2.40 | 0.903–6.377 |
Mohmand* | 39 | 35.5 | 110 | 9.2 | 2.47 | 1.046–5.841 |
Gujjar* | 31 | 40.3 | 77 | 6.4 | 3.03 | 1.244–7.394 |
Swati* | 22 | 42.3 | 52 | 4.3 | 3.30 | 1.285–8.475 |
Utman Khel* | 22 | 45.8 | 48 | 4.0 | 3.81 | 1.467–9.881 |
Yousafzai* | 69 | 46.0 | 150 | 12.5 | 3.83 | 1.670–8.797 |
Khattak* | 195 | 46.5 | 419 | 34.9 | 3.92 | 1.778–8.630 |
Afghan* | 30 | 49.2 | 61 | 5.1 | 4.36 | 1.743–10.883 |
Pela Khel* | 37 | 59.7 | 62 | 5.2 | 6.66 | 2.657–16.693 |
Others (n < 39)* | 49 | 52.1 | 94 | 7.8 | 4.90 | 2.060–11.654 |
Nuclear | 406 | 43.7 | 929 | 77.3 | Ref. | – |
Extended | 124 | 45.4 | 273 | 22.7 | 1.07 | 0.817–1.406 |
Up to 5* | 52 | 55.3 | 94 | 7.8 | 2.99 | 1.600–5.594 |
6–10* | 218 | 50.8 | 429 | 35.7 | 2.50 | 1.496–4.166 |
11–15 | 130 | 39.4 | 330 | 27.5 | 1.57 | 0.929–2.654 |
16–20 | 106 | 39.7 | 267 | 22.2 | 1.59 | 0.932–2.717 |
20+ | 24 | 29.3 | 82 | 6.8 | Ref. | – |
Up to 5 | 166 | 43.5 | 382 | 31.8 | Ref. | – |
6–9 | 272 | 44.6 | 610 | 50.7 | 1.05 | 0.809–1.355 |
10 or more | 92 | 43.8 | 210 | 17.5 | 1.01 | 0.722–1.425 |
Traditionally arranged | 345 | 38.7 | 891 | 74.1 | Ref. | – |
Arranged–love* | 185 | 59.5 | 311 | 25.9 | 2.32 | 0.552–0.723 |
#Distribution of consanguineous unions was statistically significant in the chi-square test statistics
*Significant in regression analyses
ICF, inbreeding coefficient F; OR, odd ratio; 95% CI, 95% confidence interval; Ref., reference
The prevalence of consanguinity was found inversely related to the area of house or dwelling size. The highest prevalence of consanguinity was found for individuals living in a small dwelling (55.3%), and the lowest prevalence of consanguinity was found for individuals living in larger dwellings ≥20 marla (506 m2;
We further investigated whether area of house was associated with “number of persons” in the house. A Spear-man correlation did not find any significant correlation between these 2 variables (
With respect to marriage arrangement, consanguinity was observed to be significantly higher in individuals who had arranged–love marriages (59.5%) compared with those (38.7%) who had traditionally arranged marriages (
In multivariable logistic regression, stepwise likelihood ratios were estimated. For convenience, all the parameters were initially put into two models. In the first model, the tehsil, rural/urban origin, literacy, age, occupation, and monthly income of the participant were considered. Among these, only tehsil emerged as a significant predictor of consanguinity. In the second model, year of marriage, caste system, “household type” (i.e., nuclear vs extended), area of house, number of family members, and marriage arrangement were used. Here, caste system, area of house and marriage arrangement were significantly associated with consanguinity. In the final model, all the parameters were incorporated. In this case, tehsil, age, year of marriage, caste system, area of house, and marriage arrangement were significant, while rural/urban origin, literacy, occupation, monthly income, household type, and number of family members were not (
Significant predictors of consanguinity in Mardan population observed through multivariate logistic regression
Variable | OR | Std. Err. | 95% CI | |
---|---|---|---|---|
Mardan | Ref. | |||
Katlang | 1.26 | 0.22 | 0.19 | 0.89–1.79 |
Takht Bhai | 1.68 | 0.29 | 0.003 | 1.20–2.35 |
≤1985 | Ref. | 0.16 | 0.048 | 0.33–0.99 |
1986–1995 | 0.57 | |||
1996–2005 | 0.53 | 0.17 | 0.048 | 0.28–0.99 |
2006–2015 | 0.34 | 0.12 | 0.003 | 0.17–0.69 |
Up to 30 | 2.52 | 0.92 | 0.011 | 1.23–5.14 |
30.1–40 | 1.88 | 0.60 | 0.050 | 1.00–3.53 |
40.1–50 | 1.45 | 0.41 | 0.18 | 0.84–2.52 |
≥50 | Ref. | |||
Makori | Ref. | 2.42 | 0.004 | 1.60–12.88 |
Dewan Khel | 4.54 | |||
Mohmand | 2.81 | 1.29 | 0.024 | 1.14–6.92 |
Gujjar | 3.20 | 1.52 | 0.015 | 1.26–8.14 |
Swati | 4.49 | 2.26 | 0.003 | 1.67–12.06 |
Utman Khel | 4.09 | 2.08 | 0.005 | 1.52–11.06 |
Yousafzai | 4.05 | 1.79 | 0.002 | 1.70–9.61 |
Khattak | 4.87 | 2.05 | 0.000 | 2.13–11.13 |
Afghan | 4.56 | 2.23 | 0.002 | 1.75–11.89 |
Pela Khel | 9.29 | 4.59 | 0.000 | 3.53–24.44 |
Others | 4.93 | 2.26 | 0.001 | 2.01–12.12 |
20+ | Ref. | |||
16–20 | 1.31 | 0.38 | 0.34 | 0.75–2.31 |
11–15 | 1.28 | 0.36 | 0.38 | 0.74–2.24 |
6–10 | 2.01 | 0.57 | 0.013 | 1.16–3.50 |
Up to 5 | 2.61 | 0.90 | 0.005 | 1.34–5.12 |
Traditionally arranged | Ref. | |||
Arranged–love | 2.58 | 0.37 | <0.0001 | 1.95–3.41 |
OR, odd ratio; Std. Err., standard error; 95% CI, 95% confidence interval; Ref., reference
In Pakistan, about half of marriages are contracted between individuals who are SCs or closer [4, 11]. In the population of Mardan, the prevalence of consanguinity was found to be lower than that reported for other populations of KPK and Punjab provinces. For instance, in districts of KPK,
Significant predictors of consanguinity in individual
Variable | OR | Std. Err. | 95% CI | |
---|---|---|---|---|
Urban | Ref. | |||
Rural | 1.82 | 0.47 | 0.019 | 1.10–3.01 |
Traditionally arranged | Ref. | |||
Arranged–love | 4.10 | 1.10 | <0.0001 | 2.43–6.93 |
Up to 5 | 5.63 | 3.61 | 0.007 | 1.60–19.80 |
6–10 | 6.22 | 3.41 | 0.001 | 2.12–18.22 |
11–15 | 2.20 | 1.21 | 0.15 | 0.75–6.44 |
16–20 | 1.97 | 1.09 | 0.23 | 0.65–5.86 |
20+ | Ref. | |||
Traditionally arranged | Ref. | |||
Arranged–love | 3.68 | 1.09 | <0.0001 | 2.06–6.58 |
Urban | Ref. | |||
Rural | 0.05 | 0.05 | 0.003 | 0.01–0.36 |
Up to 30 | 2.90 | 1.47 | 0.036 | 1.07–7.85 |
30.1–40 | 2.11 | 0.96 | 0.10 | 0.87–5.14 |
40.1–50 | 1.39 | 0.54 | 0.40 | 0.64–2.99 |
50+ | Ref. | |||
1985 or earlier | Ref. | |||
1986–1995 | 0.91 | 0.37 | 0.81 | 0.41–2.01 |
1996–2005 | 0.73 | 0.33 | 0.49 | 0.29–1.79 |
2006–2015 | 0.48 | 0.24 | 0.15 | 0.18–1.30 |
Makori | Ref. | |||
Dalazak | 1.58 | 0.96 | 0.45 | 0.48–5.17 |
Dewan Khel | 1.00 | Empty | ||
Mohmand | 4.42 | 2.42 | 0.006 | 1.52–12.91 |
Gujjar | 2.83 | 1.56 | 0.059 | 0.96–8.33 |
Swati | 3.55 | 2.22 | 0.043 | 1.04–12.10 |
Utman Khel | 6.95 | 4.17 | 0.001 | 2.15–22.51 |
Yousafzai | 4.29 | 2.17 | 0.004 | 1.59–11.56 |
Khattak | 7.44 | 3.54 | <0.0001 | 2.93–18.92 |
Afghan | 3.23 | 1.82 | 0.038 | 1.07–9.74 |
Pela Khel | 12.94 | 12.29 | 0.007 | 2.01–83.25 |
Others (n < 39) | 4.67 | 2.43 | 0.003 | 1.68–12.95 |
OR, odds ratio; Std. Err., standard error; 95% CI, 95% confidence interval; Ref., reference.
consanguinity was reported to be 66% in Malakand in 2014 and 55% in Peshawar in 2006 [13, 14]. The prevalence of consanguinity in Mardan was also lower than the prevalence estimated for Bhimber in 2010 (62%) [3], Sargodha in 2010–2011 (57%) [11], and Gujranwala in 1985–1986 (59%) [20]. The lowest prevalence of consanguinity ever reported in Pashtun populations was in Bajour (22.3%) in 2012 [4] and Quetta (31.6%) in 1994 [23].
By contrast with previous studies, in population in Mardan, we found no significant association between consanguinity and variables such as rural origin, literacy, occupation, income, family/household type, and number of family members [6, 7, 11, 20].
The prevalence of consanguinity was found to vary significantly across different
The lower prevalence of consanguinity in Mardan and Katlang
When the year of marriage was examined, we found a slightly declining trend in the prevalence consanguineous unions over the past 20 years or so, but this was not significant. In the multivariable analyses, year of marriage was a significant variable in the overall sample as it was in the Takht Bhai tehsil, and a pronounced temporal decline in consanguinity was predicted (
Area of house was considered as an indicator of socioeconomic status. The current study showed that consanguinity was negatively associated with area of house, and a small-sized house was a significant predictor of consanguinity in the overall data and in the Katlang and Takht Bhai
Here, we also analyzed marriage arrangement as a potential predictor of consanguinity. Marriage arrangement appeared to be a significant predictor in the overall data and in Mardan and Katlang
Among the 7 types of marital unions, FC and DR marriage types are helpful in getting an insight into the social structure of a population. FC unions indicate marriages among close blood relatives, while DR marriages may show the alliance with extended brotherhood or
The caste/
The present study has several limitations. We could not acquire complete data regarding the parental marriage types of the respondents, and the marriage data of one generation have been used to calculate ICF. In populations where there is a long tradition of close unions, the calculation of ICF from one generation could be an underestimate. Data were not gathered from women because of social and cultural constraints. The convenience sampling of ever-married men may result in sampling error and may not truly represent the population. The income categories may not be truly representative of the economic status as respondents were generally reluctant to disclose their income. Similarly, occupation is a
Despite its limitations, the present study is to our knowledge, nevertheless, the first report on the prevalence of consanguinity and highlights important aspects of consanguineous unions in a multiethnic Pashtun metropolis. The present investigation found that consanguinity was not associated with sociodemographic variables such as rural/urban origin, literacy, occupation, monthly income, household type, and number of family members of male respondents; however, a different combination of variables appeared to be factors for consanguinity in the overall district of Mardan and among the individual