Age-Stratified 30-day Rehospitalization and Mortality and Predictors of Rehospitalization Among Patients With Systemic Lupus Erythematosus: A Medicare Cohort Study

DISCUSSION

In this study, we found the 30-day rehospitalization risk among young adult Medicare beneficiaries with SLE to be 36%, which is 40% higher than young adult beneficiaries without SLE, and 85% higher than older beneficiaries with SLE. Young adult beneficiaries with SLE were more racially diverse, were from more disadvantaged neighborhoods, and had a higher burden of comorbidities than middle-aged and older adult beneficiaries with SLE. Our models had moderate-to-good predictive ability for 30-day rehospitalization among beneficiaries with SLE using geo-linked administrative data, demonstrating value for risk stratification. Medical school affiliation of the index hospital was protective for readmissions among young adults with SLE in this Medicare sample. This may indicate positive effects of programs or policies at medical school–affiliated hospitals and potential for wider dissemination efforts. To our knowledge, this is among the first studies to evaluate readmissions for young adults with SLE. It adds to findings from multipayor SLE cohorts that have reported associations of younger age with greater emergency department (ED) use⁹ and direct healthcare costs.³⁷ Our findings underscore the high rehospitalization risk among young adult Medicare beneficiaries with SLE and suggest the need to include young adults with SLE in targeted efforts to reduce rehospitalization.

In Kangovi and Grande’s framework for readmissions, rehospitalization is a result not only of inpatient care quality and patient health status but also outpatient care quality, access to care, and patient socioeconomic resources.¹¹ Uniquely, our models incorporated rich information on the social determinants of health: patient’s neighborhood disadvantage (comprising 17 indicators of socioeconomic resources), Medicaid status, and rurality. We found that the highest risk group, young adult beneficiaries with SLE, lived in more disadvantaged socioeconomic contexts, with a median neighborhood disadvantage index 16 percentile points higher than the US median, and 91% qualified for Medicaid. Young adult Medicare beneficiaries with SLE were also highly diverse at 52% Black and 15% Hispanic. Reduced access to care for Black and Hispanic Americans compared to White Americans is well documented, and prior research has shown these groups may also receive lower-quality SLE care.^38,39

An inverse relationship between age and rehospitalization rates has been observed in other early-onset chronic conditions, such as type 1 diabetes.⁴⁰ Young adults with SLE may disproportionately experience additional barriers to outpatient services (eg, childcare, transportation), potentially contributing to their higher rates of rehospitalization. In the general population, those aged 18 to 39 years were 10% more likely than adults aged ≥ 55 years to report nonfinancial barriers leading to delayed or unmet care⁴¹.

To obtain Medicare coverage, individuals aged < 65 must have ESRD or have qualified for Social Security Disability Insurance benefits for ≥ 24 months.⁴² The 5-step qualification process begins by confirming an income of < $1070/month. Young adults with SLE additionally had higher prevalence of many significant comorbid conditions than any other SLE age group (Table 1). In addition to HCC risk score and renal failure status, several other comorbidities potentially related to SLE pathophysiology (coagulopathy, CHF, fluid and electrolyte disorders, and paralysis) were selected for model inclusion. Notably, renal failure was not associated with odds of rehospitalization. Fluid and electrolyte disorders may have captured the sequalae of renal failure that predict rehospitalization. While obstetrical hospitalizations had significantly lower rehospitalization rates among beneficiaries without SLE, obstetrical hospitalizations of beneficiaries with SLE still had high levels of rehospitalization. This suggests readmission reduction efforts should extend to obstetrical care for patients with SLE.

Among young and middle-aged adults, drug use disorder was associated with increased rehospitalization odds. Patients with SLE often need chronic pain management as part of their SLE treatment and are 2 to 3 times more likely to be taking prescribed opioids than patients without SLE, with greater prevalence of previous opioid-related encounters among young adults with SLE.^43,44 Thus, these findings raise concerns about the contribution of substance use disorders, particularly in relation to prescribed opioids, to rehospitalization.

Among young adults with SLE, index hospitalization at a medical school–affiliated hospital was associated with lower odds of rehospitalization. This aligns with previous literature showing higher quality of care and lower 30-day postdischarge mortality for major teaching hospitals compared to nonacademic hospitals for many common inpatient conditions.^45,46 Our finding prompts interest in identifying practices at academic centers that may reduce rehospitalization for potential dissemination.

Our models outperformed prior US population-based studies on health condition-specific readmission risk prediction using retrospective administrative data, which reported moderately predictive models (C statistic range 0.55-0.65).¹⁵ Our method, combining a priori and LASSO-selected variables, including a neighborhood-level social determinant of health index, performed better (C statistic range 0.67-0.77) than those in the literature. These results suggest the value of incorporating location-based metrics of SES, such as the ADI, in readmission risk prediction models. Such metrics are now freely accessible and can be integrated into both retrospective administrative and real-time electronic health record data.^27,47 Notably, while the fit of age-specific models revealed some unique significant predictors in each age group, it had little effect on overall predictive value compared to the model developed with patients of all ages. The presented SLE-specific prediction models can aid healthcare and insurance systems in deciding where to focus resources to reduce rehospitalizations by risk-stratifying among the high-risk SLE patient population.

While there are many strengths of this study, including a large national cohort of patients with SLE, we acknowledge some limitations. Since this study used claims data, we do not have some patient health measures, such as functional status or current SLE disease activity. Individuals aged < 65 years must meet additional requirements to receive Medicare benefits. Thus, results for patients aged < 65 years may not generalize to the US population with SLE, particularly patients with better health status, lower prevalence of ESRD, or those unable to navigate disability qualification. However, one-third of individuals with SLE in the US have public insurance and one-half of SLE-related hospitalizations and ED visits are covered by Medicare or Medicaid,^10,48,49 making this cohort relevant to practice and policy. Higher rates of ED use among young adult patients with SLE in a multipayor SLE cohort⁹ suggest that the higher risk of acute healthcare use in young adult patients with SLE is not unique to Medicare beneficiaries. Poor health status of Medicare beneficiaries also underscores the importance of developing interventions for this group. Reported race and ethnicity in Medicare data have known issues with misclassification.^22,23 While we used the more valid RTI measure, approximately 4% of patients may be misclassified. Native American and Asian patients are more likely to be misclassified,²² which could affect comparisons involving these groups. As administrative data were used in this study, conditions and billing codes may not have been uniformly coded for all beneficiaries. However, previously validated, published algorithms for administrative data were used to define SLE and other comorbidities.^18,31 Coding bias may also have been reduced since all individuals in the cohort had the same insurance coverage.

While Medicare covers many patients with SLE, multipayor or Medicaid cohorts should be evaluated to compare rates and validate the rehospitalization predictors among young adults, including more patients without ESRD. Further research comparing rehospitalization reasons should be performed among young adults with SLE. Additional evaluations are needed of socioeconomic resource and access barriers for young adults with SLE and their relation to rehospitalization, ambulatory vs acute care use, and healthcare costs. For Medicare SLE-related hospitalizations, the administrative data-based predictive models had moderate-to-good predictive value and could be applied to prioritize patients with SLE for readmission interventions. These areas of inquiry can be leveraged to inform program and policy development to reduce rehospitalization and improve care for young adults with SLE.

Young adult Medicare beneficiaries with SLE were 40% more likely to be rehospitalized within 30 days compared to age matched beneficiaries without SLE and 85% more likely than older beneficiaries with SLE. This elevated rehospitalization rate among young adults with SLE in Medicare may be partially explained by higher neighborhood disadvantage and greater prevalence among Black and Hispanic patients, who generally have reduced access to healthcare and receive lower-quality SLE care than White patients.^38,39 Young adult beneficiaries with SLE also had more comorbidities, which increased their odds of rehospitalization. The presented SLE-specific prediction models had moderate-to-good prediction for 30-day rehospitalization, informing risk stratification. Together, these findings suggest a critical need to develop targeted interventions, alongside young adults with SLE, to provide greater outpatient support, address disease management barriers, and reduce costly rehospitalizations.