Mental illness and length of inpatient stay for Medicaid recipients with AIDS

Health Services Research, Oct, 2004 by Donald R. Hoover, Usha Sambamoorthi, James T. Walkup, Stephen Crystal

The adjusted models in Table 2 also suggest that for persons with AIDS, time to readmission was 2 percent to 16 percent shorter for visits in all categories of acute mental illness and mental illness history than for visits of other patients with similar characteristics, but no history of mental illness. Uldall et al. (1998) (in unadjusted analysis) also found that hospitalized AIDS patients "ever diagnosed with a psychiatric morbidity" had shorter times to hospital readmission than did persons not diagnosed with psychiatric morbidity. Quicker readmission may reflect that in addition to HIV diseases, AIDS patients with mental illness also experience mental disorders that need hospitalization, perhaps due to inadequate treatment of mental illnesses at current or prior visits.

The associations between indicators of severity of disease and access to health care on the one hand, and LOS and TR on the other that were observed in this study, are mostly expected and consistent with prior findings (Kelly, Ball, and Turner 1989; Stein 1994; Bonuck and Arno 1997; Dal Pan, Skolasky, and Moore 1997). Diagnosis of a major opportunistic AIDS illness at the visit was associated with an adjusted 42 percent increase in LOS, which is only somewhat greater than the 32 percent increase in LOS associated with a primary diagnosis of severe mental illness. This indicates that hospitalization time needed for primary severe mental illness episodes among persons with AIDS may be comparable to that needed for advanced AIDS diseases.

The most notable associations with LOS and TR observed in this study are for calendar trends from 1992 to 1998. Mean LOS declined by more than 4.5 days and TR increased by ~6 months. After adjusting for year of visit, our variable for use of PI/NNRTI by the patient was associated with only a 10 percent reduction in LOS and had no association with TR. However, this likely is an underestimate since we incorporated PI/NNRTI as an intent-to-treat variable (once started always considered using PI/NNRTI) to eliminate well-known selection biases related to ability to stay on these regimens; for example, the sickest patients may not be able to tolerate treatment (Glesby and Hoover 1996). Furthermore, we only have data prior to 1999. If recent widespread use of PI/NNRTI has further reduced the time needed to hospitalize for HIV (but not for mental illness), current associations between diagnoses of acute Primary and Secondary severe mental illnesses and hospitalization time for AIDS patients could now be even greater than those reported here.

Some potential study limitations should be noted. We studied New Jersey Medicaid patients and it cannot be ruled out that association between mental illness and hospital LOS for AIDS patients differs between countries and by insurance coverage in the United States. The data available in Medicaid claims limit our ability to utilize criteria of duration and severity of mental illness to define subgroups of interest; the bias here should be conservative (harder to find associations with mental illness) since some patients with history of mental illness may be not be identified as such, and misclassified as no mental illness. As our measures of chronic mental illness were based on number of contacts with the medical system, there is also some bias toward identification of Mental Illness History in patients who had had longer contact with the medical system. However, as all patients had been diagnosed with AIDS by 1996 and data were collected until the end of 1998, we believe this bias was small. Some patients may have gone off of Medicaid eligibility during the evaluation period, which might make time to readmission estimates for these persons unreliable. Even the large number of variables we used to adjust for stage of disease and access to health care may still not be able to remove all confounding with mental illness. Most notably, we did not have CD4 counts, a strong predictor of HIV disease progression. If those diagnosed with mental illness were more likely to be at earlier stages of AIDS, this could create a conservative bias.