Ethnic disparities in causes of death among diabetes patients in the Waikato region of New Zealand

Aim: Assist health service planning by: (1) estimating the causes and disparities in mortality among people with diabetes in Waikato and (2) examining the differences in recording of diabetes. Method: A retrospective cohort study of diabetes patients registered with the Waikato Regional Diabetes Service. Deaths from 2003-2007 were identified among patients diagnosed with diabetes before 2003. Causes of death were obtained from the NZHIS. Mortality rates were compared with the general New Zealand population. Cox's proportional-hazards- model was used to estimate the all-cause and cause-specific mortality risk. Results: 921 deaths were observed among 9043 diabetes patients. Compared with Europeans, Maori had nearly double the age-adjusted mortality rates. SMRs for male-Europeans, female-Europeans, male-Maori and female-Maori aged 25+ were 1.16 (1.05-1.28), 1.10 (0.98-1.24), 2.49 (2.06-3.01), 3.12 (2.56-3.80) respectively. Of the 441 deaths with causes available, 268 (61%) had diabetes mentioned on the NZHIScoding. Maori were more likely than Europeans to have diabetes reported on NZHIScoding. They were more likely to die from cardiovascular disease, cancer and renal disease [Hazard-ratios 2.31 (1.6-3.3), 1.83 (1.1-3), and 11.74 (4.8-29) respectively]. Conclusion: Maori diabetes patients experienced significantly higher risk of mortality compared with Europeans. Studies on diabetes related mortality using the national mortality database needs to take the increased recognition of diabetes on NZHIS coding for Maori into account.