Of the 5,007,820 patients included in this study, 14.3% had 1 readmission, 2.4% had 2+ non-clustered readmissions, and 3.3% patients had 2+ clustered readmissions during the 270-day follow-up window. The study population was mostly female (of older age; 65–79), resided in a low-income zip code, publicly insured (Medicare and Medicaid), had a hospitalization during the pre-HRRP era, and lived in large fringe metropolitan areas (Tables 1 and 2). Subgroups with the highest proportions of patients with multiple 30-day readmissions were those discharged to home or self-care, on government insurance (Medicare/Medicaid), and with increasing numbers of comorbidities and those that had chronic ACSCs. Prevalence of ACSCs during index hospitalizations is presented in Fig. 2.
Table 1 Frequency of ACSC Index Hospitalizations for Readmission Subgroups, by Social Determinant Factors, Health Status Indicators, and Other Clinical Factors (Nationwide Readmissions Database, 2010–2014) Table 2 Frequency (by Row Percent) of ACSC Index Hospitalizations for Readmission Subgroups, by Social Determinant Factors, Health Status Indicators, and Other Clinical Factors (Nationwide Readmissions Database, 2010–2014) Our multivariable regression analyses exploring factors associated with readmission frequency and patterns are presented in Table 3. The measures of association for the social determinant factors varied. Women had decreased odds of having 1 readmission (AOR = 0.93; CI = 0.92, 0.94), 2+ non-clustered readmissions (AOR = 0.97; CI = 0.95, 0.99), and 2+ clustered readmissions (AOR = 0.87; CI = 0.86, 0.89) than men. Patients living in zip codes reporting the lowest household income quartiles, compared to reporting the highest, had increased odds of having 1 readmission (AOR = 1.09; CI = 1.07, 1.10) and 2+ non-clustered readmissions (AOR = 1.24; CI = 1.20, 1.29) and higher odds of 2+ clustered readmissions (AOR = 1.21; CI = 1.18, 1.26). Differences were observed by insurance type; patients with any insurance other than private had increased odds of having 1 readmission (Medicare: AOR = 1.43, CI = 1.40, 1.46; Medicaid: AOR = 1.53, CI = 1.50, 1.56; self-pay/no charge/other: AOR = 1.01, CI = 0.99, 1.04), 2+ non-clustered readmissions (Medicare: AOR = 2.04, CI = 1.95, 2.13; Medicaid: AOR = 2.29, CI = 2.20, 2.40; self-pay/no charge/other: AOR = 1.13, CI = 1.07, 1.19), and 2+ clustered readmissions (Medicare: AOR = 2.12, CI = 1.18, 1.26; Medicaid: AOR = 2.57, CI = 2.47, 2.67; self-pay/no charge/other: AOR = 1.18, CI = 1.13, 1.24). Patients who lived in large central metropolitan areas, compared to those living in smaller populated areas, experience decreased odds of 1 readmission and 2+ clustered readmissions, compared to 0 readmissions.
Table 3 Adjusted Odds Ratios and 95% Confidence Intervals from Survey Logistic Regression Representing Factors Associated with Readmission Frequency and Patterns (Nationwide Readmissions Database, 2010–2014) Several health status factors were associated with increased odds of readmission. Compared to those aged 80+ years, all other younger age groups had increased odds for 2+ non-clustered readmissions (18–44 years: AOR = 2.03, CI = 1.94, 2.13; 45–64 years: AOR = 1.61, CI = 1.55, 1.67; 65–79 years: AOR = 1.27, CI = 1.23, 1.31) and 2+ clustered readmissions (18–44 years: AOR = 2.49, CI = 2.39, 2.58; 45–64 years: AOR = 1.70, CI = 1.65, 1.75; 65–79 years: AOR = 1.28, CI = 1.25, 1.32). Those with more substantial loss of function—a proxy for severity of the condition resulting in the index hospitalization—experienced increased odds for 1 readmission (moderate: AOR = 1.33, CI = 1.31, 1.36; major: AOR = 1.64, CI = 1.61, 1.68; extreme: AOR = 1.86, CI = 1.81, 1.91), 2+ non-clustered readmissions (moderate: AOR = 1.47, CI = 1.40, 1.53; major: AOR = 1.79, CI = 1.71, 1.88; extreme: AOR = 1.79, CI = 1.69, 1.90), and 2+ clustered readmissions (moderate: AOR = 1.51, CI = 1.46, 1.57; major: AOR = 1.87, CI = 1.79, 1.94; extreme: AOR = 1.94, CI = 1.85, 2.04). Patients with chronic ACSCs, compared to acute ACSCs, had higher odds of 1 readmission (AOR = 1.37; CI = 1.36, 1.39), 2+ non-clustered readmissions (AOR = 2.69; CI = 2.62, 2.76), and 2+ clustered readmissions (AOR = 2.03; CI = 1.99, 2.07). Similarly, there was a direct association between increased numbers of Elixhauser comorbidities—reflecting the patient’s co-occurring conditions not directly tied to the index hospitalization’s principal diagnosis—and both the frequency of readmissions and the likelihood of clustering of readmissions (Table 3).
Other clinical factors were also associated with readmission patterns. Patients sent to home health or transferred to another facility and left against medical advice had higher odds, compared to those sent home, for 1 readmission (transfer/home health: AOR = 1.35, CI = 1.34, 1.37; against medical advice: AOR = 1.84, CI = 1.78, 1.91), 2+ non-clustered readmissions (transfer/home health: AOR = 1.26, CI = 1.22, 1.29; against medical advice: AOR = 1.81, CI = 1.68, 1.94), and 2+ clustered readmissions (transfer/home health: AOR = 1.28, CI = 1.26, 1.31; against medical advice: AOR = 2.62, CI = 2.49, 2.75), compared to 0 readmissions. Patients whose index hospitalizations required emergency department services and those who received care at larger, metropolitan teaching hospitals were at highest odds of experiencing multiple and/or clustered readmissions.
Compared to the pre-HRRP, patients in the post-HRRP period had lower odds for all readmission types: for 1 readmission, 0.95 (0.93, 0.96); for 2+ non-clustered readmissions, 0.87 (0.85, 0.89); and for 2+ clustered readmissions, 0.88 (0.86, 0.90).