Social disparities in unplanned 30-day readmission rates after hospital discharge in patients with chronic health conditions: A retrospective cohort study using patient level hospital administrative data linked to the population census in Switzerland

Unplanned readmissions shortly after discharge from hospital are common in chronic diseases. The risk of readmission has been shown to be related both to hospital care, e.g., medical complications, and to patients' resources and abilities to manage the chronic disease at home and to make appropriate use of outpatient medical care. Despite a growing body of evidence on social determinants of health and health behaviour, little is known about the impact of social and contextual factors on readmission rates. The objective of this study was to analyse possible effects of educational, financial and social resources of patients with different chronic health conditions on unplanned 30 day-readmission risks on the individual level. The study made use of nationwide inpatient hospital data that was linked with Swiss census data. The sample included n=62,109 patients aged 25 and older, hospitalized between 2012 and 2016 for one of 12 selected chronic condition. Multivariate logistic regressions analysis was performed. Patients with upper secondary education (OR=1.26, 95% CI: 1.11, 1.44) and compulsory education (OR=1.51, 95% CI: 1.31, 1.74) had higher readmission rates than those with tertiary educa-tion when taking into account demographic, social and health status factors. Having (semi-) private hospital insurance (OR=0.81, 95% CI: 0.73, 0.90) were associated with a lower risk for 30-day readmis-sion compared to patients with mandatory insurance. The risk of readmission for patients with chronic conditions was, however, most strongly predicted by factors related to health status, such as type of chronic condition (up to 4.5 times more likely), previous hospitalizations before the index hospitaliza-tion (+77%) and additional comorbidities (+15% higher probability per unit) as well as by particularly long hospitalizations (+64%). Stratified analysis by type of chronic condition revealed differential ef-fects of education level on readmissions risks. Compulsory education was significantly associated with higher odds only for lung cancer (+142%), congestive heart failure (+63%) and back problems (+53%). We did not find a general effect of social resources, measured by living with others in a household, on readmission rates. Our results indicate significant differences by socioeconomic status, in particular by education level, in the risk of unplanned readmission after hospitalization among patients with chronic conditions. We assume that low educational attainment among chronically ill patients increases the risk of unplanned 30-day readmission after hospitalisation due to factors related to their social situation (e.g., low health literacy, lower financial possibilities), which may negatively affect cooperation with care providers and adherence to recommended therapies as well as hamper active participation in the medical process and the development of a shared understanding of the disease and its cure. Higher level of comorbidity and severity of illness of socially disadvantaged patients further complicate ade-quate self-management and outpatient care use. Our findings suggest a need for increased preven-tive measures for disadvantaged populations groups to promote early detection of diseases and to remove financial or knowledge-based barriers to medical care. Socially disadvantaged patients should also be strengthened more in their individual and social resources for coping with illness.