RATIONALE: Cognitive impairment is one of the most common complaints for persons with epilepsy (PWE). These impairments are not only associated with seizures, but are also regularly reported as adverse effects of antiepileptic drugs (AEDs). Previous studies have examined cognitive effects of both AED monotherapy and polytherapy, yet there is limited research on these differences with respect to both subjective and objective cognition. The current study uses data from previous research conducted by the Centers for Disease Control and Prevention (CDC)-sponsored Managing Epilepsy Well (MEW) Network collaborative. We used three distinct archival datasets from the following: (1) the HOBSCOTCH efficacy trial at Dartmouth-Hitchcock Medical Center (HOB-1), (2) the multisite replication trial (HOB-2), and (3) epilepsy self-management research conducted at the NYU School of Medicine.
METHODS: This retrospective analysis combined baseline data from three datasets to determine how the number of AEDs and the type of AEDs were associated with subjective (patient-reported) and objective (examiner-assessed) cognition. Subjective cognition was captured using the cognitive subscale of the Quality of Life in Epilepsy Inventory (QOLIE-31) in all three datasets (n = 224), while objective cognition was measured using the Repeated Battery for the Assessment of Neuropsychological Status (RBANS) in the HOB-1 dataset (n = 65) and the Brief Test of Adult Cognition by Telephone (BTACT) in the HOB-2 dataset (n = 91). Multivariable linear regression was utilized for our initial assessments, followed by propensity score matching to provide stronger control of covariates. Matching was based on significantly different covariates, such as education, depression, and history of prior epilepsy surgery. Nonparametric statistical tests were utilized to compare these matched subjects.
RESULTS: Subjective cognitive impairment was significantly worse among individuals on monotherapy (1 AED) compared with those on polytherapy (2+ AEDs) (adjusted p = 0.041). These findings were consistent with the propensity score matched comparison of monotherapy and polytherapy, which indicated that polytherapy was associated with worse overall subjective cognition (adjusted p = 0.01), in addition to impairments on the RBANS (Total score p = 0.05) and specific subdomains of the BTACT (Episodic Verbal Memory p < 0.01, Working Memory p < 0.01, Processing Speed p < 0.01). Interestingly, older generation AEDs were associated with better language performance than newer generation and combined generation AED therapy (RBANS Language p = 0.03). These language-specific findings remained significant after controlling for the effects of topiramate and zonisamide (p = 0.04).
CONCLUSIONS: A greater number of antiepileptic drugs (AEDs) is significantly and negatively associated with subjective and objective cognition in people with epilepsy, and is in line with previous research. Antiepileptic drug type did not, in itself, appear to be associated with subjective cognition. These findings suggest that ineffective AEDs should be replaced, rather than introducing additional AEDs to a treatment regimen. Further, while subjective and objective cognition assessments were both sensitive at detecting differences based on AED status, the neuropsychological objective subdomains offer additional and specific insights into how cognition is impaired with AEDs.