Limitations and potential of country of birth as proxy for ethnic group

Editor—We agree with Jarman and Aylin that recording of ethnic group on death certificates needs to be improved in the United Kingdom.¹

Currently, country of birth has been included in each UK census since 1841 and is a readily available and objective, although crude, method of ethnic group classification.² Indeed it remains a good proxy for ethnic group for the older age minority groups and is of intrinsic interest in separating environmental and genetic differences. However, it is no longer an appropriate proxy as it does not take account of the diversity of the country of origin of the individual; the number of white people born in countries, such as India, ruled by the British Empire; and children of migrants identified by this method as second generation immigrants. In the 2001 census half of the minority ethnic population was born outside the United Kingdom.

Further recording of country of birth on death certificates, which is reliant on an informant, may be less accurate than on the census, when the person is still alive to provide the information, leading to the possibility of numerator-denominator bias. Previous analyses of mortality by country of birth have grouped together countries for which this is a particular issue—South Asian countries³—but this approach obscures potentially important differences between countries of birth.²,³,⁴

Despite these limitations, we have documented the marked variations in mortality by age, sex, and ethnic group.⁵ This resource is available online and provides a wide range of data both on the morbidity and mortality by ethnic group that is of use for commissioning services for these minority communities. However, there is an urgent need to address the recording of ethnic group data on death certificates to accurately determine and address the health inequalities between ethnic groups in the United Kingdom.