Analysis of in-hospital mortality among people with and without diabetes in South Western Sydney public hospitals (2014-2017)

Background: Diabetes is a major public health problem affecting about 1.4 million Australians, especially in South Western Sydney, a hotspot of diabetes with higher than average rates for hospitalisations. The current understanding of the international burden of diabetes and related complications is poor and data on hospital outcomes and/or what common factors influence mortality rate in people with and without diabetes in Australia using a representative sample is lacking. This study determined in-hospital mortality rate and the factors associated among people with and without diabetes. Methods: Retrospective data for 554,421 adult inpatients was extracted from the population-based New South Wales (NSW) Admitted Patient Data over 3 financial years (from 1 July 2014–30 June 2015 to 1 July 2016–30 June 2017). The in-hospital mortality per 1000 admitted persons, standardised mortality ratios (SMR) were calculated. Binary logistic regression was performed, adjusting for potential covariates and co-morbidities for people with and without diabetes over three years. Results: Over three years, 8.7% (48,038 people) of admissions involved people with diabetes. This increased from 8.4% in 2014–15 to 8.9% in 2016–17 (p = 0.007). Across all age groups, in-hospital mortality rate was significantly greater in people with diabetes (20.6, 95% Confidence intervals CI 19.3–21.9 per 1000 persons) than those without diabetes (11.8, 95%CI 11.5–12.1) and more in men than women (23.1, 95%CI 21.2–25.0 vs 17.9, 95%CI 16.2–19.8) with diabetes. The SMR for those with and without diabetes were 3.13 (95%CI 1.78–4.48) and 1.79 (95%CI 0.77–2.82), respectively. There were similarities in the factors associated with in hospital mortality in both groups including: older age (> 54 years), male sex, marital status (divorced/widowed), length of stay in hospital (staying longer than 4 days), receiving intensive care in admission and being admitted due to primary respiratory and cardiovascular diagnoses. The odds of death in admission was increased in polymorbid patients without diabetes (28.68, 95%CI 23.49–35.02) but not in those with diabetes. Conclusions: In-patients with diabetes continue to have higher mortality rates than those without diabetes and the Australian population. Overall, similar factors influenced mortality rate in people with and without diabetes, but significantly more people with diabetes had two or more co-morbidities, suggesting that hospital mortality may be driven by those with pre-existing health/comorbidities. Urgent measures in primary care to prevent admissions among people with multiple co-morbidities are needed.