Abstract
Significant ethnic and socio-economic disparities exist in infectious diseases (IDs) rates in New Zealand, so accurate measures of these characteristics are required. This study compared methods of ascribing ethnicity and socio-economic status. Children in the Growing Up in New Zealand longitudinal cohort were ascribed to self-prioritised, total response and single-combined ethnic groups. Socio-economic status was measured using household income, and both census-derived and survey-derived deprivation indices. Rates of ID hospitalisation were compared using linked administrative data. Self-prioritised ethnicity was simplest to use. Total response accounted for mixed ethnicity and allowed overlap between groups. Single-combined ethnicity required aggregation of small groups to maintain power but offered greater detail. Regardless of the method used, Māori and Pacific children, and children in the most socio-economically deprived households had a greater risk of ID hospitalisation. Risk differences between self-prioritised and total response methods were not significant for Māori and Pacific children but single-combined ethnicity revealed a diversity of risk within these groups. Household income was affected by non-random missing data. The census-derived deprivation index offered a high level of completeness with some risk of multicollinearity and concerns regarding the ecological fallacy. The survey-derived index required extra questions but was acceptable to participants and provided individualised data. Based on these results, the use of single-combined ethnicity and an individualised survey-derived index of deprivation are recommended where sample size and data structure allow it.
Highlights
The epidemiology of infectious disease (ID) in New Zealand (NZ) is marked by significant ethnic and socio-economic disparities, with higher rates observed in Māori and Pacific peoples, and in areas of greater socio-economic deprivation.[1,2,3]
A single total-response ethnicity was identified for 3062 (54.7%) children with the remainder having multiple ethnicities identified. As some of these multiple ethnicities fell within the same broad ethnic group, 3880 (69.3%) children had a single total response ethnic group
A majority of children in each total response ethnic group were self-prioritised to the corresponding group, as shown in Supplementary Table S2
Summary
The epidemiology of infectious disease (ID) in New Zealand (NZ) is marked by significant ethnic and socio-economic disparities, with higher rates observed in Māori and Pacific peoples, and in areas of greater socio-economic deprivation.[1,2,3] Likewise, higher rates of ID are seen in indigenous and marginalised ethnic minority groups in comparable developed countries such as Australia and the USA [4, 5]. Accurate measures of ethnic identity and socio-economic deprivation are of particular importance in epidemiological research. Ethnicity is a complicated social construct that describes cultural identity or affiliation [6]. There are a number of methods of ascribing ethnicity in epidemiological research including selfprioritisation, total response and single-combined ethnicity, each method having its advantages and disadvantages [7]. Socio-economic deprivation can be measured in various ways, including by directly questioning household income, and by using census-derived geographic measures [8] or survey-derived individual measures [9]
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