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Adherence Suffers When OOP Drug Costs for Neurologic Disorders Rise, Study Shows


Higher out-of-pocket (OOP) drug costs for 3 common neurologic conditions—Parkinson disease, Alzheimer disease, and peripheral neuropathy—were associated with lower medication adherence among patients, which can potentially intensify symptom burden and result in higher costs.

Higher out-of-pocket (OOP) drug costs for 3 common neurologic conditions—Parkinson disease (PD), Alzheimer disease, and peripheral neuropathy—were associated with lower medication adherence among patients, according to study findings published today in the journal Neurology.

Treatment adherence is vital to patients with neurologic conditions such as PD, since non-adherence can hinder quality of life (QOL) and promote the frequency of symptom recurrence after a period of symptom control, known as OFF periods.

During these events, the ability and productivity of employment in patients with PD (PwP) are significantly impeded, causing many to stop working due to complications. Moreover, caregivers of PwP undergoing OFF periods reported that reoccurrence of symptoms had a greater impact in loss of earnings, loss of opportunities, or ability to maintain employment compared with caregivers for PwP without OFF periods.

In 2013, study authors note that neurologist-prescribed medications accounted for approximately $5 billion in Medicare Part D payments (4.8% of total payments) and has continued to increase with the introduction of novel, high-priced drugs in the market. The financial burden imposed by rising prescription drug costs have additionally began to be shifted more toward patients with neurologic disorders through OOP costs, as shown in a prior analysis by the study authors.

Previously, OOP costs were shown to be associated with treatment non-adherence in patients with rheumatoid arthritis and diabetes, with 3 studies also showing this trend for neurologic medications among patients with multiple sclerosis. Researchers sought to examine whether this link additionally applied to patients with common neurologic disorders such as Alzheimer disease, peripheral neuropathy, and PD.

In the study, researchers derived medical and pharmaceutical claims from the deidentified Clinformatics Datamart (OptumInsight, Eden Prairie, MN) database on patients with 1 of the 3 neurologic conditions who were prescribed medications with similar efficacy and tolerability, but different OOP costs over a 15-year period (2001-2016). The primary outcome of medication adherence was determined by how many days’ worth of each drug was supplied to a patient within the first 6 months.

The study included patients with Alzheimer disease and other dementia who were administered cholinesterase inhibitors (n = 19,820), patients with neuropathy given gapapentinoids (n = 52,249) or mixed serotonin/norepinephrine reuptake inhibitors (SNRIs) (n = 5246), and PwP administered dopamine agonists (n = 3130). An instrumental variable analysis was used to estimate the association of OOP costs and other patient factors on medication adherence.

Researchers found that increases in OOP costs by $50 were associated with significantly lower medication adherence among patients with neuropathy on gabapentinoids (adjusted incidence rate ratio [IRR] = 0.91; CI, 0.89—0.93) and dementia (adjusted IRR = 0.88; CI, 0.86–0.91). Conversely, there was no significant association found between increased OOP costs and medication adherence for patients with neuropathy on SNRIs (adjusted IRR = 0.97; CI, 0.88–1.08) and PwP (adjusted IRR = 0.90; CI, 0.81–1.00). However, these populations did exhibit decreased treatment adherence.

Study author Brian Callaghan, MD, MS, professor of neurology at the University of Michigan in Ann Arbor and a fellow of the American Academy of Neurology, stressed his concern at the study findings, especially with a growing transition to OOP costs for patients. “Of course, if people do not follow their prescriptions correctly, they are less likely to benefit from the drug and see improvements in their condition, possibly leading to complications and higher costs later,” said Callaghan.

Compared with white patients, researchers found that Asian, black, and Latino participants experienced larger drops in medication adherence for equivalent increases in OOP costs, highlighting the potential risk posed to minority populations with neurologic diseases. “New approaches to increase medication adherence for these population groups is critically important to reducing health care disparities," said Callaghan.

To address the inflating financial burden posed on patients with neurologic diseases, James Stevens, MD, president of the American Academy of Neurology, stated that systematic changes are warranted. "These changes could include legislative action to place a cap on out-of-pocket costs, which the American Academy of Neurology is advocating for in Washington, D.C.,” said Stevens. “Another change could be to provide neurologists with access to information on drugs costs so that when they meet with patients to make treatment decisions, they can help to minimize the financial burden.”

Limitations to the study included the measurement of data solely for patients with private insurance, which may not apply to other populations. Additionally, researchers were unable to measure how many people did not fill their first prescription of a drug, potentially affecting findings related to OOP costs.


Reynolds EL, Burke JF, Banerjee M, et al. Association of out-of-pocket costs on adherence to common neurologic medications [published online February 19, 2020]. Neurology. doi: 10.1212/WNL.0000000000009039.

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