Who are Pacific peoples in terms of ethnicity and country of birth? A cross sectional study of 2,238,039 adults in Aotearoa New Zealand's Integrated Data Infrastructure.

Background: The aggregation of Indigenous peoples from Pacific Island nations as 'Pacific peoples' in literature may mask diversity in the health needs of these different groups. The aim of this study was to examine the heterogeneity of Pacific groups according to ethnicity and country of birth. Methods: Anonymised individual-level linkage of administrative data identified all NZ residents aged 30-74 years on 31 March 2013 with known ethnicity and country of birth. All participants were described according to ethnicity and country of birth. Pacific participants were also described according to the number of ethnicities they identified. Findings: A total of 2,238,039 NZ residents were included, of whom 117,957 (5·0%) were Pacific. Nearly two-thirds of Pacific peoples (65·7%) were born overseas, ranging from 45·3% (Cook Islands Māori) to 82·7% (Fijian) (Māori 2·3%, non-Māori non-Pacific 28·9%). Among NZ-born Pacific peoples, 46·9% (Samoan) to 81·9% (Fijian) were multi-ethnic; the proportion was much lower for overseas-born Pacific peoples (ranging from 3·7% [Tongan] to 23·9% [Tokelauan]). Interpretation: There is substantial heterogeneity among Pacific peoples in their country of birth and identification with sole or multiple ethnicities. Assumptions regarding homogeneity in the needs of Pacific peoples are not appropriate and government statistics should therefore disaggregate Pacific peoples whenever possible. Funding: Supported by the Health Research Council of New Zealand and a part of Manawataki Fatu Fatu, a programme of research funded by the National Heart Foundation of New Zealand and Healthier Lives - He Oranga Hauora - National Science Challenge of New Zealand.