Consanguinity in Spain: socioeconomic, demographic, and geographic influences

Information on consanguinity in Spain was reanalyzed in order to obtain a more complete picture of consanguinity patterns by considering temporal, geographical, demographic, and economic factors. To obtain data on consanguineous marriages, we reviewed 106 published references. Only populations with homogeneous geographical characteristics, economic activities, transportation facilities, and the like, were considered. Two-way analysis of variance (ANOVA) provided highly significant differences (p < 0.001) for a both for time periods and for urban versus rural patterns, but there was no interaction between the latter two. A regression analysis shows that for rural areas the geographic characteristics, economy, communications, and index of demographic tendency were significant predictors of the inbreeding coefficient. The results obtained indicate that urban and rural patterns differ significantly and that the temporal factor needs to be taken into account before comparing inbreeding coefficients. In urban areas the census size and altitude are included in the regression equation as significant variables, but association was not found between alpha and the index of demographic tendency (population increase or decrease). Instead, the absolute number of inhabitants (census size) was significant. In rural areas geographic characteristics, communications, and index of demographic tendency were significant predictors of the inbreeding coefficient.