Private insurance versus medicaid and adherence to medication in older adults with fibromyalgia

Background: Fibromyalgia, defined as chronic, wide-spread musculoskeletal pain, affects 4 to 10 million Americans and up to 6% of the world population. Medication nonadherence results in $100 to$300 billion in US health expenditures annually. Previous studies have examined medication adherence in commercial health plans or public health plans, but relatively few have compared both populations. The purpose of this study was to estimate the effect of type of insurance on adherence to medication for older adults with fibromyalgia. Methods: The retrospective cohort study analyzed medical claims of fibromyalgia patients collected between January 1, 2005 to June 30, 2011 from the Blue Cross Blue Shield South Carolina State Health Plan (BCBS) and Medicaid data. Older adults age 60 and older were included if they were prescribed duloxetine, milnacipran, or pregabalin (N=3,187). The primary outcome, medication adherence, was defined as having a medication possession ratio (MPR) of ≥ 80%. Independent variables included health insurance, FMS medication, selected comorbidities (FMS-related, musculoskeletal pain, or neuropathic pain), gender, age, and the interaction between health insurance type and treatment. Results: Logistic regression showed older adults with fibromyalgia on Medicaid were over 3 times more likely to be adherent when compared to BCBS in both unadjusted (OR: 3.21, p<0.0001) and adjusted models (OR: 3.74, p<0.0001). Conclusion: Most states do not require a Medicaid prescription co-pay; whereas, private insurers, like Blue Cross Blue Shield, require more out-of-pocket costs. Our study suggests that the co-pays for medications in private plans may present a barrier to patient adherence