Income‐Related Differences in the Use of Evidence‐Based Therapies in Older Persons with Diabetes Mellitus in For‐Profit Managed Care

ObjectivesTo determine whether income influences evidence-based medication use by older persons with diabetes mellitus in managed care who have the same prescription drug benefit.DesignObservational cohort design with telephone interviews and clinical examinations.SettingManaged care provider groups that contract with one large network-model health plan in Los Angeles County.ParticipantsA random sample of community-dwelling Medicare beneficiaries with diabetes mellitus aged 65 and older covered by the same pharmacy benefit.MeasurementsPatients 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.ResultsThe 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.ConclusionAmong 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