Mental comorbidity and quality of diabetes care under Medicaid: a 50-state analysis

Patients with comorbid medical and mental conditions are at risk for poor quality of care. With the anticipated expansion of Medicaid under health reform, it is particularly important to develop national estimates of the magnitude and correlates of quality deficits related to mental comorbidity among Medicaid enrollees.

For all 657,628 fee-for-service Medicaid enrollees with diabetes during 2003 to 2004, the study compared Healthcare Effectiveness Data and Information Set (HEDIS) diabetes performance measures (hemoglobin A1C, eye examinations, low density lipoproteins screening, and treatment for nephropathy) and admissions for ambulatory care-sensitive conditions (ACSCs) between persons with and without mental comorbidity. Nested hierarchical models included individual, county, and state-level measures.

A total of 17.8% of the diabetic sample had a comorbid mental condition. In adjusted models, presence of a mental condition was associated with a 0.83 (0.82-0.85) odds of obtaining 2 or more HEDIS indicators, and a 1.32 (1.29-1.34) increase in odds of one or more ACSC hospitalization. Among those with diabetes and mental comorbidities, living in a county with a shortage of primary care physicians was associated with reduced performance on HEDIS measures; living in a state with higher Medicaid reimbursement fees and department of mental health expenses per client were associated both with higher quality on HEDIS measures and lower (better) rates of ACSC hospitalizations.

Among persons with diabetes treated in the Medicaid system, mental comorbidity is an important risk factor for both underuse and overuse of medical care. Modifiable county and state-level factors may mitigate these quality deficits.