The relationship between hospital admission rates and rehospitalizations.

BACKGROUND Efforts to reduce hospital readmissions have focused primarily on improving transitional care. Yet variation in readmission rates may more closely reflect variation in the underlying hospitalization rates than differences in the quality of care during and after discharge. METHODS We used national Medicare data to calculate, for each local hospital referral region (HRR), the 30-day, 60-day, and 90-day readmission rates among patients discharged with congestive heart failure or pneumonia. We also calculated population-based all-cause admission rates among Medicare enrollees in each HRR. We examined the variation in HRR readmission rates that was explained by overall hospitalization rates versus differences in patients' coexisting conditions, quality of discharge planning, physician supply, and bed supply. RESULTS HRR readmission rates ranged from 11 to 32% for congestive heart failure and from 8 to 27% for pneumonia. In univariate analyses, all-cause admission rates accounted for the highest proportion of regional variation in readmission rates for congestive heart failure (28%, 34%, and 37% at 30, 60, and 90 days, respectively); the next highest proportions were explained by case mix (11%, 15%, and 18%) and the number of cardiologists per capita (12%, 14%, and 15%). Results for pneumonia were similar, except that the number of pulmonologists per capita accounted for a lower proportion of the variation (6%, 8%, and 7%, respectively). In multivariate analyses, admission rates accounted for 16 to 24% of the variation for congestive heart failure and 11 to 20% for pneumonia; no other factor accounted for more than 6%. CONCLUSIONS We found a substantial association between regional rates of rehospitalization and overall admission rates. Programs directed at shared savings from lower utilization of hospital services might be more successful in reducing readmissions than programs initiated to date. (Funded by the Commonwealth Fund.).