Objectives

To determine whether income influences evidence-based medication use by older persons with diabetes mellitus in managed care who have the same prescription drug benefit.

Design

Observational cohort design with telephone interviews and clinical examinations.

Setting

Managed care provider groups that contract with one large network-model health plan in Los Angeles County.

Participants

A random sample of community-dwelling Medicare beneficiaries with diabetes mellitus aged 65 and older covered by the same pharmacy benefit.

Measurements

Patients reported their sociodemographic and clinical characteristics. Annual household income (> or =$20,000 or <$20,000) was the primary predictor. The outcome variable was use of evidence-based therapies determined by a review of all current medications brought to the clinical examination. The medications studied included use of any cholesterol-lowering medications, use of 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) for cholesterol lowering, aspirin for primary and secondary prevention of cardiovascular disease, and angiotensin-converting enzyme (ACE) inhibitors in those with diabetic nephropathy. The influence of income on evidence-based medication use was adjusted for other patient characteristics.

Results

The cohort consisted of 301 persons with diabetes mellitus, of whom 53% had annual household income under $20,000. In unadjusted analyses, there were lower rates of use of all evidence-based therapies and lower rates of statin use for persons with annual income under $20,000 than for higher-income persons. In multivariate models, statin use was observed in 57% of higher-income versus 30% of lower-income respondents with a history of hyperlipidemia (P =.01) and 66% of higher-income versus 29% of lower-income respondents with a history of myocardial infarction (P =.03). There were no differences by income in the rates of aspirin or ACE inhibitor use.

Conclusion

Among these Medicare managed care beneficiaries with diabetes mellitus, all of whom had the same pharmacy benefit, there were low rates of use of evidence-based therapies overall and substantially lower use of statins by poorer persons.