Reviewing causes of death of individuals with intellectual disability in New South Wales, Australia: a record-linkage study

Background People with intellectual disability (ID) have a much higher mortality rate than the general population. To reduce the rate of mortality of people with ID, it is critical that causes of death are properly understood, recorded and reported. Formal reviews of causes of death are used in some countries to ensure that causes of death are accurate. To date, the impact of these formal reviews on understanding causes of death of people with ID has not been quantified. Methods The study aimed to quantify the impact of formal reviews of deaths on the understanding of causes of death of people with ID who died while living in residential care. Individuals (851) with ID who died in residential care in New South Wales (NSW), Australia, between 1 December 2002 and 31 December 2013, who had a cause of death recorded in both the NSW Cause of Death Unit Record File (COD-URF; cause of death recorded at time of death) and NSW Ombudsman dataset (cause of death recorded after in-depth review) were included in the study. We assessed agreement in coding for cause of death by comparing the International Classification of Diseases 10th Revision (ICD-10) codings at three levels of diagnostic specificity, for both underlying and additional causes of death. We conducted our analysis through both descriptive comparison and through two boosted regression trees. Results Approximately half of the underlying causes of death were different after review by the NSW Ombudsman compared with the COD-URF. Certain causes of death (determined by ICD-10 chapter) were less likely to predict matches between the dataset than others, with individuals with mental, behavioural and neurodevelopmental disorders recorded in the COD-URF least likely to have a matching cause of death in NSW Ombudsman dataset. For deaths where there was no agreement at any level between the datasets, a high level of unknown causes of death was recorded. Conclusions Formal review of deaths of people with ID in residential care is important to determining true causes of death and therefore developing appropriate health policy for people with ID.