Acknowledgements The authors would like to thank June Atkinson for preparing the data for analysis. Funding The study was funded by the National Institute of Water and Atmospheric Research (NIWA). The New Zealand Census Mortality Study is conducted in collaboration with Statistics New Zealand and within the conﬁnes of the Statistics Act 1975. The New Zealand Census Mortality Study study was funded by the Health Research Council of New Zealand, and receives continuing funding from the Ministry of Health. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing interests None. Contributors TB conceived the analysis and contributed to the design, interpretation and revision of drafts. SH performed the analyses, drafted the text of the paper and contributed to the design and interpretation of results. 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