Deaths with Dementia in Indigenous and Non-Indigenous Australians: A Nationwide Study

Abstract

Background: The prevalence of dementia is generally reported to be higher among Indigenous peoples. Objective: The rates and coding of dementia mortality were compared between Indigenous and non-Indigenous Australians. Methods: De-identified individual records on causes of death for all people aged 40 years or more who died in Australia between 2006 and 2014 (n = 1,233,084) were used. There were 185,237 records with International Classification of Diseases, Tenth Revision, codes for dementia (Alzheimer’s Disease, vascular dementia, or unspecified dementia) as the underlying cause of death or mentioned elsewhere on the death certificate. Death rates were compared using Poisson regression. Logistic regression was used to assess whether dementia was more likely to be classified as ‘unspecified’ type in Indigenous Australians. Results: The rates of death with dementia were 57% higher in Indigenous Australians, compared to non-Indigenous, relative rate (RR) 1.57, 95% confidence interval (CI) (1.48, 1.66), p < 0.0001. This excess of deaths was highest at ages below 75 (RRs > 2, test for interaction p < 0.0001), and among men (test for interaction p < 0.0001). When the underreporting of Indigenous status on the death certificate was taken into account the relative rate increased to 2.17, 95% CI (2.07, 2.29). Indigenous Australians were also more likely to have their dementia coded as ‘unspecified’ on their death certificate (Odds Ratio 1.92, 95% CI (1.66, 2.21), p < 0.0001), compared to the non-Indigenous group. Conclusion: This epidemiological analysis based on population level mortality data demonstrates the higher dementia-related mortality rate for Indigenous Australians especially at younger ages.