Our sample included a total of 124,967 diabetes patients 50 years of age or older who were discharged alive from California hospitals between April and September 2006. The majority were aged between 65 and 79, female, White, and Medicare patients (). These diabetes patients had about 3.8 chronic conditions each, on average (not shown)’ about 16.2% had a hospitalization history in the 3 months prior to the index hospitalization’ and only about one fifth (18.4%) of their index hospitalizations were scheduled at least 24 hours in advance. The most common reason for the index hospitalization was congestive heart failure (7.9%), followed by diabetes with complications (7.5%), coronary artherosclerosis (4.9%), and pneumonia (4.1%).
Descriptive statistics, readmission rates, and risk factors of scheduled and unscheduled readmissions
Approximately twenty-six percent (n=32,857) of the patients were readmitted within 0–3 months of their index hospitalizations, and a majority of the readmissions (87.2%) were unscheduled (). The risks for unscheduled and scheduled readmission varied by patients’ demographic, socioeconomic, and clinical characteristics (). While adjusting for other factors, patients aged 80 or older were slightly more likely (Odds Ratio [OR]=1.07[95% CI 1.02–1.12], compared to those aged between 50 and 64) to have an unscheduled readmission. Blacks (OR=1.17[1.11–1.23]) and Hispanics (OR=1.10[1.07–1.14]) were also more likely to have an unscheduled readmission than Whites. Patients with public insurance had a higher risk for an unscheduled readmission compared to patients with private insurance (OR for Medicare patients=1.39[1.33–1.46], & OR for Medicaid patients=1.53[1.45–1.62]). Patients residing in urban areas (OR=1.16[1.09–1.22], compared to rural) and those residing in lower income neighborhoods (OR=1.11[1.07–1.16], compared to higher income neighborhoods) had higher risks for an unscheduled readmission. The risk for unscheduled readmission consistently increased as the number of chronic conditions that a patient had increased: patients with 7 or more chronic conditions were nearly three times more likely to have an unscheduled readmission than those with diabetes only (OR=2.93[2.52–3.41]). An unscheduled readmission was more likely to occur in patients who had had one or more hospitalizations in the 3 months preceding the index hospitalization (OR=2.17[2.10–2.25]). Also, the risk for an unscheduled readmission increased when the index hospitalization was an unscheduled admission (OR=1.72[1.64–1.80]), or when it ended with a transfer to another post-acute or long-term institution (OR=1.28[1.24–1.32]). As length of stay rose, the likelihood of unscheduled readmission increased.
Some factors predicting unscheduled readmissions also predicted scheduled readmissions in the same way: compared to men, women were less likely to have a scheduled readmission (OR=0.75[0.70–0.80]), but people with Medicare as the primary payer (OR=1.15[1.04–1.26]) were more likely to do so. The number of chronic conditions and length of stay also positively predicted the odds for both unscheduled and scheduled readmissions. Two other factors predicted both scheduled and unscheduled readmissions, but the directions were opposite: people aged 80 or over (OR=0.71[0.63–0.79], compared to people aged 50–64) and those with unscheduled index hospitalizations (OR=0.58[0.47–0.71], compared to scheduled index hospitalizations) were more likely to have an unscheduled readmission, but less likely to have a scheduled readmission. Unlike these factors, factors that positively predicted an unscheduled readmission but not a scheduled readmission were being an ethnic minority (compared to being White), having Medicaid as the primary payer (compared to private insurance), resident location, median income of the neighborhood, and disposition destination. Being uninsured negatively predicted a scheduled readmission only (OR=0.58[0.53–0.62], compared to people with private insurance).
The most common 15 diagnoses for both unscheduled and scheduled readmissions, covering more than 50% of all of those readmissions, are listed in . The most frequent condition among diabetes patients with an unscheduled readmission was congestive heart failure (8.8%), followed by diabetes mellitus with complications (7.2%), septicemia (5.8%), and pneumonia (3.9%). Among patients with scheduled readmissions, diabetes mellitus with complications (7.1%) was the third most common diagnosis, following coronary atherosclerosis (11.4%) and complications of device, implant, or graft (7.3%). Only 6 out of 15 conditions—congestive heart failure, diabetes mellitus with complications, complications of device, complications of surgical procedures or medical care, coronary atherosclerosis, and cardiac dysrhythmias—were common to both unscheduled and scheduled readmissions. In addition, 3 out of those 6 conditions—congestive heart failure, complication of device, and coronary atherosclerosis—were in very different ranks among unscheduled and scheduled readmissions.
Common clinical conditions for scheduled and unscheduled readmissions
Lastly, about 19.0% of unscheduled readmissions (n=5,432) were potentially preventable (). Among the eight conditions that can be managed in the ambulatory setting according to AHRQ’s PQI definitions, congestive heart failure, bacterial pneumonia, and urinary tract infections were the three most frequent conditions in our sample of hospitalized middle-aged and older diabetes patients. These potentially preventable unscheduled readmissions made up a total of 27,477 inpatient days and cost nearly $72.7 million. Among the 4,208 patients with scheduled readmissions, only 140 (3.3%) were categorized as potentially preventable using the same PQI definitions, comprising about 862 inpatient days and $1.9 million (not shown).
Prevalence of and service use for potentially preventable unscheduled readmissions (PPURs)