Mental retardation and consanguinity
in ethnic minorities in the County of Copenhagen.

Ugeskr Læger 2003;165:42-6.

Introduction: In the County of Copenhagen the treatment of mentally retarded (MR) children is centralised in the Center for Handicapped (CFH). The aim of this study was to elucidate whether the frequency of MR is higher in children from ethnic minorities than in the background population and whether an increase could be ascribed to inbreeding.

Material and methods: The medical records of children with a non-Danish family name and where both parents were from countries other than Denmark were studied.

Results: A significant increase in the frequency of MR were found in the children from ethnic minorities: 16.6% of the children seen at CFH had an ethnic background compared to 14% in the background population, making a surplus of 18.5% more than expected. When a family was inbred other family members had MR in 43.0%, whereas more family members with MR were found in only 14.2% of the families with no inbreeding. In the consanguineous families we found possible aetiological diagnoses in 21.5% of the children compared to 49% in the non-consanguineous families. In the entire group of children from ethnic minorities, we found Down's syndrome in 3.2% compared to 10.7% in Danish children with MR.

Discussion: There is a surplus of MR in children from ethnic minorities in the County of Copenhagen. The causes are not known, nor are aetiological factors for MR for a great part of the children. Consanguinity is likely to be a risk factor for MR, especially if it is already present in the family. This conforms with previously published data from other countries.