Incidence of and predictors for antiseizure medication gaps in Medicare beneficiaries with epilepsy: a retrospective cohort study

Abstract

Background For the two-thirds of patients with epilepsy who achieve seizure remission on antiseizure medications (ASMs), patients and clinicians must weigh the pros and cons of long-term ASM treatment. However, little work has evaluated how often ASM discontinuation occurs in practice. We describe the incidence of and predictors for sustained ASM fill gaps to measure discontinuation in individuals potentially eligible for ASM withdrawal. Methods This was a retrospective cohort of Medicare beneficiaries. We included patients with epilepsy by requiring International Classification of Diseases codes for epilepsy/convulsions plus at least one ASM prescription each year 2014–2016, and no acute visit for epilepsy 2014–2015 (i.e., potentially eligible for ASM discontinuation). The main outcome was the first day of a gap in ASM supply (30, 90, 180, or 360 days with no pills) in 2016–2018. We displayed cumulative incidence functions and identified predictors using Cox regressions. Results Among 21,819 beneficiaries, 5191 (24%) had a 30-day gap, 1753 (8%) had a 90-day gap, 803 (4%) had a 180-day gap, and 381 (2%) had a 360-day gap. Predictors increasing the chance of a 180-day gap included number of unique medications in 2015 (hazard ratio [HR] 1.03 per medication, 95% confidence interval [CI] 1.01–1.05) and epileptologist prescribing physician (≥25% of that physician’s visits for epilepsy; HR 2.37, 95% CI 1.39–4.03). Predictors decreasing the chance of a 180-day gap included Medicaid dual eligibility (HR 0.75, 95% CI 0.60–0.95), number of unique ASMs in 2015 (e.g., 2 versus 1: HR 0.37, 95% CI 0.30–0.45), and greater baseline adherence (> 80% versus ≤80% of days in 2015 with ASM pill supply: HR 0.38, 95% CI 0.32–0.44). Conclusions Sustained ASM gaps were rarer than current guidelines may suggest. Future work should further explore barriers and enablers of ASM discontinuation to understand the optimal discontinuation rate.

Frequency of and factors associated with antiseizure medication discontinuation discussions and decisions in patients with epilepsy: A multicenter retrospective chart review

“…Some previous work has examined factors associated with ASM withdrawal. 19,20 For example, one study 20 found an increased chance of treatment discontinuation in children, and cases with cryptogenic etiologies, fewer seizures, and normal neuroimaging. Our study builds upon those findings by adding in adjusted estimates, adding in a All patients in this cohort were determined seizure-free at least one year.…”

“…It was also interesting that discontinuation was so rare in older patients, which echoes prior work. 19 ASMs have special implications for aging-related comorbidities given ASMs are associated with a relative risk of falls, 30 enzyme-inducing ASMs increase osteoporosis 31 and lipids, 32,33 and ASMs may worsen cognition throughout life 5,34 beyond the known bidirectional relationship between epilepsy and dementia. 35 Still, caution may be appropriate in older patients given unique psychosocial concerns regarding injury from seizures in the context of declining bone health or potential anticoagulation or fear of losing independence.…”

“…Some previous work has examined factors associated with ASM withdrawal 19,20 . For example, one study 20 found an increased chance of treatment discontinuation in children, and cases with cryptogenic etiologies, fewer seizures, and normal neuroimaging.…”

“…Literature exploring the determinants of withdrawal is sparse. 19,20 One survey documented variation in how likely clinicians were to endorse discontinuing ASMs for several patient vignettes. 21 Yet, hypothetical intent may not translate into practice, and selected vignettes reflect a small portion of real-world complexity.…”

“…However, that study included only self‐reported patient data, was not stratified by key variables (e.g., seizure‐free duration, post‐discontinuation risk), and did not include children. Literature exploring the determinants of withdrawal is sparse 19,20 . One survey documented variation in how likely clinicians were to endorse discontinuing ASMs for several patient vignettes 21 .…”