The European Journal of Public Health Advance Access originally published online on October 5, 2005
The European Journal of Public Health 2006 16(3):290-293; doi:10.1093/eurpub/cki201
Ethnic Disparities in Health |
Infant mortality, ethnicity, and genetically determined disorders in The Netherlands
Tom W.J. Schulpen1, Joke C.M. van Wieringen1, Pien J. van Brummen1, Jantien M. van Riel1, Frits A. Beemer2, Paul Westers3 and Jonne Huber4
1 Centre for migration and child health, University Medical Centre Utrecht, The Netherlands
2 Department of medical genetics, University Medical Centre Utrecht, The Netherlands
3 Centre for Biostatistics, Utrecht University, Utrecht, The Netherlands
4 Department of pathology, University Medical Centre Utrecht, The Netherlands
Correspondence: Prof. Tom W.J. Schulpen, MD, PhD, MPH, Paediatric Association of The Netherlands, PO Box 20059, 3502 LB Utrecht, The Netherlands, tel: +31 30 2823762, e-mail: Schulpen{at}worldonline.nl
Received November 19, 2004, accepted August 30, 2005
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Abstract |
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Background: Infant mortality of ethnic minorities in The Netherlands (10% of the population) is twice as high as in the indigenous Dutch population. Causes of death are different for the diverse migrant groups. Methods: Hospital records of nearly 600 infants who died in the four major cities between 1995 and 1998 were analysed according to the cause of death, ethnicity, and possible hereditarity. Results: There was a four to five times higher proportion of hereditary causes of death in the Moroccan and Turkish population, compared with the Surinamese/Antillians and indigenous Dutch. Conclusions: This might be explained by a high inbreeding coefficient as three-quarters of the marriage partners are recruited from the home villages and between a quarter and a third of these marriages are between first cousins. Health promotion activities in The Netherlands have not been successful so far. Preconception genetic counselling might help in reducing these differences.
Keywords: consanguinity, ethnicity, genetics, infant mortality, The Netherlands
The Netherlands with 16 million inhabitants has sizable groups of ethnic minorities, mounting to 10% of the population. There are around 270 000 Moroccans and 320 000 Turks who came to The Netherlands during the sixties as migrant labourers and were followed by their families in the eighties. The Dutch colony of Surinam in South America became independent in 1975 and over 200 000 persons (blacks and Hindustani) came to The Netherlands, soon followed by around 80 000 Carribeans from The Netherlands Antilles. At present 310 000 Surinamese and 120 000 Antillians are living in The Netherlands. The number of refugees and asylum seekers who yearly enter The Netherlands has lowered from about 40 000 in the years before 2001 to <14 000 in 2003.1
Differences in perinatal and childhood mortality rates between ethnic groups have been reported in several countries.2–4 In The Netherlands two national surveys on this subject were held.5
One survey concerned a retrospective analysis of 569 743 births from the national obstetric registry between 1990 and 1993. Perinatal death (including stillbirth) was significantly higher in the black population (odds ratio 2.2) and in the population from Mediterranean origin (odds ratio 1.3), compared with the indigenous Dutch population.6 The increased rate in the black population could be fully explained by preterm birth, while teenage pregnancy, grande multiparity, and socio-economic status explained the difference for the Mediterranean group.
Further analysis of the underlying causes of differences in perinatal and infant mortality according to prosperity scores at neighbourhood level revealed that ethnicity is a more important predictor than socio-economic status, followed by age and parity of the mother.7
The second survey on childhood death (0–14 years) analysed the death certificates of 20 211 children, who died between 1979 and 1993 in The Netherlands. The death of Turkish and Moroccan children was twice as high as that of indigenous Dutch children. For the different diagnostic categories the relative risk was 2.2 for infectious diseases, 2.0 for hereditary (metabolic) disorders, and 1.9 for accidents and drowning. One quarter of the Turkish and Moroccan children died while on holiday in their country of origin. Sudden Infant Death syndrome (SIDS) was twice as high for Turkish infants as for Dutch infants and four times higher than for Moroccan infants.8
In order to gain further insight in the above mentioned differences, originally aimed at detecting differences in Sudden Infant Death (0–2 years), a new, more detailed survey was conducted in the four major cities, where nearly half of the migrant population of The Netherlands lives.
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Methods |
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Data of all live born children (0–2 years) who died in the years 1995, 1996, and 1997 in one of the four major cities (Amsterdam, Rotterdam, The Hague, and Utrecht) were collected from the local population registry with ethnicity registered according to the official definition of the Ministry of Internal Affairs.
In total 827 children of the total population of over 2 million inhabitants of these four major cities had died during this period before their second birthday. Most children die in hospital. Information about pregnancy, birth, socio-economic situation, and circumstances during the moment of death was taken from hospital records during visits to all hospitals in the four major cities. Only children registered as inhabitant of the city concerned were included. Hospital records of 592 children (71.6%) could be retrieved, the others died at home, in a hospital outside their hometown or abroad while being on holiday. Analysis of the non-retrieved cases gave no major differences in ethnicity, age, or sex. The final cause of death as registered by the paediatrician in charge in the hospital, sometimes after having received laboratory and genetic results, was classified by two independent researchers according to ICD-9.
Statistical analysis was performed with SPSS, differences in death rate between the ethnic groups were tested with the 
2-test, while the causes of death and the proportion of hereditary causes of death were compared with the Fisher's exact test because of small numbers.9
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Results |
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Of the 592 children who died 56.9% were indigenous Dutch, 9.3% Moroccan, 9.3% Turkish, 9.3% Surinamese, 8.8% from other non-Western countries, and 6.4% from other Western countries.
The death rate in the four major cities within the different ethnic groups was as follows: for Surinamese/Antillians it was 0.8 per 1000 live births, for Turks 1.0, for Moroccans 0.9, for other migrants of non-Western countries 0.7, for migrants from Western countries 0.6, and for indigenous Dutch 0.5. The death rate for the three major immigrant groups (Surinamese/Antillian, Turkish, and Moroccan) were higher than for the indigenous Dutch population (P < 0.001). These results are not different from those found earlier in the national surveys.5 The total death rate in these four cities together was 0.7, which is higher than the national figure of 0.51.
Table 1 gives causes of death, grouped according to ICD-9 codes and classified by ethnicity. Among the Moroccan and Turkish population congenital malformations (hereditary and non-hereditary), metabolic diseases, and CNS disorders formed together the main cause of death. Perinatal factors are the major cause of death in the indigenous Dutch, the Surinamese/Antillian, and the other Western and non-Western population. It includes conditions like asphyxia, prematurity, or infections. The causes of death of the Turkish and Moroccan group was significantly different from the causes of death of the indigenous Dutch group (P-values are 0.001 and <0.001, respectively). This was not the case for the other groups. However, it is known from our earlier research data that within the perinatal causes of death, prematurity in the black Surinamese/Antillians was twice as high as in the indigenous Dutch.
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Table 2 gives the result of redefining and regrouping of the causes of death in hereditary and non-hereditary disorders. All diagnoses were coded by two researchers (a paediatric pathologist and a clinical geneticist). The hereditary disorders were subdivided into autosomal recessive and other hereditary disorders. There is a small number of possible hereditary disorders. The combined hereditary cause of death is 18% in the Turkish (P = 0.005), 27% in the Moroccan (P < 0.001), and 3.6% in the Surinamese/Antillian group (P = 1.0) compared with 3.6% in the indigenous Dutch group. Table 3 gives insight in the various diagnoses scored by the two experts.
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Discussion |
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This study was originally set up to detect the causes of differences of SIDS between different ethnic groups in order to find possibilities for intervention. SIDS in The Netherlands, however, has dramatically decreased from 0.7–1.0 per 1000 live born infants before 1990 to 0.25–0.17 in 1995–1997.10 This was mainly the result of the campaign in 1990 to switch the sleeping position of children from prone to backward position. Only 15 children with SIDS (0.25 per 1000) were found in this study, which is insufficient for further analysis. Analysing the data we were struck by the large number of (inherited) congenital conditions among the Turks and Moroccans. Further study on the influence of cultural habits was performed. In many Islamic countries consanguinity is common with percentages between 20–30 in Turkey and Morocco and 50–60 in Saudi Arabia.11 It is well known that consanguineous marriages carry an increased risk for birth defects and/or genetic diseases, especially autosomal recessive disorders.12–14 The more isolated and closer the community the higher the inbreeding coefficient. There is no consensus about the influence of consanguinity on congenital malformations and mortality but it is more or less accepted that consanguinity increases this risk for infant death from two to three times.15,16 Stoltenberg in Norway calculated a 4-fold increased recurrence risk of stillbirth and infant death for offspring of first-cousin parents.17 In The Netherlands, where consanguinity of couples or parents is not registered it is estimated that about a quarter to a third of Turkish and Moroccan marriages are between first degree cousins.18
The migrant population in The Netherlands mainly comes from isolated rural areas and three quarters of the young marriage partners come from the country of origin, mostly from the same village and/or family.19 This population has a low education, their socio-economic condition is poor, and many marry at very young age. They are not aware of the risks of inbreeding, contrary to the population living in the more developed regions of Turkey and Morocco, where health education is given about this subject. In The Netherlands health promotion initiatives in order to inform these migrant groups of the increased risk of congenital anomalies have been initiated but have so far not been successful. Genetic services are hardly used by the migrant population.20 Preventive services for children such as vaccinations are also used at a lower rate; however, this nearly approaches the level of indigenous Dutch children.21
An evaluation of a publicity campaign on the use of folic acid in pregnancy revealed less knowledge of ‘non-Western’ women compared with ‘Western’ women.22
Our research data are small and cover only 3 years and the extreme differences in causes of death are not representative for the population at large. We believe, however, that attention should be given to the increased risk for an inherited disorder as a cause of death.
We acknowledge the social and economic advantages of consanguineous marriages. With respect to ethnocultural practices we are convinced with others23 that better education and an increased knowledge about possibilities of genetic counselling after a careful medical family and village history can help to reduce these genetic disorders as a cause of childhood mortality.
Key points
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Acknowledgments |
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The authors wish to thank Prof. M.C. Cornel for her helpful comments. This work originates from a study carried out under a Ministry of Health grant.
There are no conflicts of interest.
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References |
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