(165) The Association of Gabapentin Use and Change of Motor Functions in Older Adults with Normal Cognition

Publication Number: 839

Background
Gabapentin has been increasingly prescribed to older adults; however, recent studies raise concerns about the safety related to misuse and adverse events (e.g., respiratory depression, dizziness, and sedation). Moreover, the relationship between gabapentin use and motor behavior changes in older adults has not been studied yet.

Objectives
We aimed to examine the association of gabapentin use and motor behavior changes in older adults with normal cognition.

Methods
A retrospective cohort study was conducted using National Alzheimer’s Coordinating Center Uniform Data Set (2005-March 2021). We identified gabapentin new-users with normal cognition at the visit of gabapentin initiation (i.e., index visit) and no history of gait disorder, falls, and slowness. New-users were matched on year of first enrollment and time of gabapentin initiation since enrollment to randomly select nonusers (1 to 9 ratio) with replacement. The outcomes of interest, including gait disorder, falls, and slowness, were defined based on clinician judgment and assessed at the first and second visits after the index visit. We used stabilized inverse probability of treatment weights and stabilized inverse probability of censoring weights to mitigate confounding and selection bias. Confounders were measured at index visit (except for smoking history and diabetes which was only available at enrollment) and included demographics (age, sex, education, and race); body mass index; smoking history; comorbidities (depression, diabetes, Parkinson’s disease, and anxiety); and medications (opioids, antiseizures, and anxiolytic, sedative, and hypnotics). They were selected using directed acyclic graphs (DAG). To account for within-participant correlations and obtain robust standard errors we used generalized estimating equations with an exchangeable working correlation structure.

Results
We included 459 new-users (mean age [SD]: 78.7 [6.9]; male 34.0%) and 4,131 nonusers (78.2 [6.9]; 34.7%), all with normal cognition at index visit. At the first follow-up visit in the study, the odds ratio (OR) and 95% confidence interval (CI) (new-users vs. nonusers) was 0.97 [0.44, 2.15] for gait disorder, 1.42 [0.61, 3.31] for falls, and 1.44 [0.70, 2.97] for slowness. At the second follow-up visit, the OR and 95% CI (new-users vs. nonusers) was 1.10 [0.54, 2.24] for gait disorder, 2.51 [1.19, 5.32] for falls, and 1.39 [0.66, 2.92] for slowness.

Conclusions
Gabapentin use was associated with increased motor function decline among older adults with initially normal cognition. Further studies are needed to determine whether this association is causal.