Inequalities in avoidable hospitalisation in large urban areas: retrospective observational study in the metropolitan area of Milan

OBJECTIVE: Significant inequalities in access to healthcare system exist between residents of world megacities, even if they have different healthcare systems. The aim of this study was to estimate avoidable hospitalisations in the metropolitan area of Milan (Italy) and explore inequalities in access to healthcare between patients and across their areas of residence. DESIGN: Retrospective observational study. SETTING: Public and accredited private hospitals in the metropolitan area of Milan. Data obtained from the hospital discharge database of the Italian Health Ministry. PARTICIPANTS: 472 579 patients hospitalised for ambulatory care sensitive conditions and resident in the metropolitan area of Milan from 2005 to 2016. OUTCOME MEASURE: Age-adjusted rates of avoidable hospitalisations; OR for hospital admissions with ambulatory care sensitive conditions. METHODS: Age-adjusted rates of avoidable hospitalisations in the metropolitan area of Milan were estimated from 2005 to 2016 using direct standardisation. For the hospitalised population, multilevel logistic regression model with patient random effects was used to identify patients, hospitals and municipalities’ characteristics associated with risk of avoidable hospitalisation in the period 2012–2016. RESULTS: The rate of avoidable hospitalisation in Milan fell steadily between 2005 and 2016 from 16.6 to 10.5 per 1000. Among the hospitalised population, the odds of being hospitalised with an ambulatory care sensitive condition was higher for male (OR 1.42, 95% CI 1.36 to 1.48), older (OR 1.012, 95% CI 1.01 to 1.014), low-educated (elementary school vs degree OR 4.23, 95% CI 3.72 to 4.81) and single (vs married OR 2.08, 95% CI 2.01 to 2.16) patients with comorbidities (OR 1.47, 95% CI 1.38 to 1.56); avoidable admissions were more frequent in public non-teaching hospitals while municipality’s characteristics did not appear to be correlated with hospitalisation for ambulatory care sensitive conditions. CONCLUSIONS: The health system in metropolitan Milan has experienced a reduction in avoidable hospitalisations between 2005 and 2016, quite homogeneously across its 134 municipalities. The study design allowed to explore inequalities among the hospitalised population for which we found specific sociodemographic disadvantages.