Quantifying the hidden healthcare cost of diabetes mellitus in Australian hospital patients.

BACKGROUND: Diabetes mellitus in hospital inpatients is most commonly present as a comorbidity rather than as the primary diagnosis. In some hospitals, the prevalence of comorbid diabetes mellitus across all inpatients exceeds 30%, which could add to complexity of care and resource utilisation. However, whether and to what extent comorbid diabetes mellitus contributes indirectly to greater hospitalisation costs is ill-defined.

AIM: To determine the attributable effect of comorbid diabetes mellitus on hospital resource utilisation in a General Internal Medical service in Melbourne, Australia.

METHODS: We extracted data from a database of all General Internal Medical discharge episodes from July 2012 to June 2013. We fitted multivariable regression models to compare patients with diabetes mellitus to those without diabetes mellitus with respect to hospitalisation cost, length of stay, admissions per year and inpatient mortality.

RESULTS: Of 4657 patients 1519 (33%) had diabetes mellitus, for whom average hospitalisation cost (AUD9910) was higher than those without diabetes mellitus (AUD7805). In multivariable analysis, this corresponded to a 1.22-fold (95% confidence interval (CI) 1.12-1.33, P < 0.001) higher cost. Mean length of stay for those with diabetes was 8.2 days versus 6.8 days for those without diabetes, with an adjusted 1.19-fold greater odds (95% CI 1.06-1.33, P = 0.001) of staying an additional day. Number of admissions and mortality were similar.

CONCLUSION: Comorbid diabetes mellitus adds significantly to hospitalisation duration and costs in medical inpatients. Moreover, diabetes mellitus patients with chronic complications had a greater-still cost and hospitalisation duration compared to those without diabetes mellitus.