Patterns of Medication Use Associated with Epilepsy and Comorbid Behavioural and Mental Disorders in Older People with Intellectual Disability

Abstract

Background: There is increasing concern worldwide regarding the levels of use and suboptimal prescribing of psychotropic medication in people with intellectual disability. Antipsychotics, in particular are often prescribed for challenging behaviours rather than a psychiatric diagnosis. A high prevalence of epilepsy can also be found in people with intellectual disability. The pro-convulsive and interactive potential of some psychotropic drugs has led to concerns of possible worsening of seizure control. Antiepileptic drugs (AEDs) may also affect mood and behaviour in people with epilepsy and intellectual disability.

Methods: Data were drawn from Wave 3 of the Intellectual Disability Supplement to the Irish Longitudinal Study on Ageing (IDS-TILDA). Medication data were available for 549 participants in Wave 3 (90.1%). For those with epilepsy, psychotropic drugs were categorised according to potential seizure threshold-lowering risk (low, moderate, high). The Behaviour Problems Inventory Short Form (BPI-S) was used to assess challenging behaviours. Antiepileptic drug (AED) load was calculated and median AED loads obtained. Non-parametric tests and binary logistic regression were performed to determine the relationship between AED load and challenging behaviours. Binary logistic regression was also performed to identify factors associated with seizure frequency and inter-class psychotropic polypharmacy.

Results: The prevalence of epilepsy was found to be 35.8% (n=196). Of participants with seizure data (n=190), 40.5% reported experiencing at least one seizure in the last year. Participants taking at least one medication classified as moderate/high risk for lowering the seizure threshold were significantly less likely to experience a seizure compared to participants taking no medication of this class after adjusting for confounders. Two-thirds of participants with an epilepsy diagnosis, reporting a regular AED and having behavioural (BPI-S) data were found to exhibit challenging behaviours. Participants with a severe/profound intellectual disability exhibiting self-injurious behaviour (SIB) and aggressive/destructive behaviour were found to have significantly higher median AED loads compared to participants not exhibiting these behaviours. Higher AED load was also found to be associated with exhibiting aggressive/destructive behaviour, after adjusting for confounders. Of participants with medication data and confirmed mental health status (n=513), six in ten participants reported taking psychotropic medication with over a third exposed to inter-class psychotropic polypharmacy. Reporting an epilepsy diagnosis was not found to be associated with inter-class psychotropic polypharmacy, adjusting for confounders.

Conclusions: This thesis highlights the significant psychiatric comorbidity associated with both epilepsy and intellectual disability. Psychotropic medication in therapeutic doses, recommended to be avoided or used with caution did not provoke increased seizure frequency in this cohort. Challenging behaviours were found to be a considerable problem for older people with intellectual disability and epilepsy. Extensive use of psychotropic medication and high levels of exposure to inter-class psychotropic polypharmacy were found in this population group. Understanding the pharmaceutical care complexities, both adverse effects and appropriateness of treatment, is a necessary step to ensuring a good quality of life for people with intellectual disability.