Factors associated with subjective cognitive function in epilepsy and psychogenic non-epileptic seizures

Highlights

• Subjective cognitive dysfunction may affect the quality of life of PWE and PNES.

• Our study assesses factors associated with subjective cognition in PWE and PNES.

• Mood disorders and poor objective cognition are significant associations.

• Subjective cognitive dysfunction warrants workup for objective cognitive decline.

• Mood disorders should be investigated in those with subjective cognitive impairment.

Abstract

Objective

To identify factors associated with subjective cognitive complaints in people with presumed seizure disorders referred for video electroencephalogram monitoring (VEM).

Methods

Adult patients admitted for inpatient VEM were recruited. Objective cognitive function was measured with the Neuropsychiatry Unit Cognitive Screening Tool, subjective cognitive function with the Quality of Life in Epilepsy Inventory-89 subscales, and anxiety and depressive symptoms with the Hospital Anxiety and Depression Scale. Multivariate Bayesian general linear models were used to identify predictors of subjective cognitive function.

Results

331 patients met inclusion criteria. Mean age was 39.3 years and 61.9 % patients were female. Diagnoses included epilepsy, psychogenic non-epileptic seizures (PNES) or both conditions. Depression, anxiety and objective cognitive function were predictors of subjective cognitive function across all domains. Depression was the strongest predictor of subjective memory and attention, whilst objective cognition was the strongest predictor of subjective language function. Mood also mediated the relationship between objective function and subjective function across all domains to varying extents; depression exerted the strongest effect of 22 % for the memory domain; conversely, language domain was least influenced by mood, with depression mediating 11 % and anxiety mediating only 9% of the subjective-objective relationship.

Significance

Mood and objective cognitive function are both important contributors to subjective cognitive function for patients undergoing VEM. Clinicians should consider referring patients with cognitive complaints for both neurocognitive workup and neuropsychiatric evaluation. Future work may examine the effects of treating concomitant mood disorders on subjective cognitive function.

Introduction

People with epilepsy (PWE) and people with psychogenic non-epileptic seizures (pwPNES) frequently complain of cognitive difficulties, and these may affect their quality of life as least as much as the seizures themselves (Miller et al., 2016; Drane et al., 2006; Giovagnoli et al., 2014). There is often overlap between epilepsy and PNES diagnoses, and PWE and pwPNES may share similar risk factors for cognitive complaints (Turner et al., 2011). Despite this, studies that examine and compare cognitive function between these groups are limited (Willment et al., 2015). Previous work has identified that depression, anxiety, and objective cognitive function may be predictive of subjective cognitive function in both PWE and pwPNES, and the investigation and optimisation of subjective cognitive function remains an important focus for clinical research (Fargo et al., 2004; Samarasekera et al., 2015).

The high prevalence of depression and anxiety in these populations is well recognised, however these mood disorders often are under-diagnosed and thus under-treated (Shehata and Bateh, 2009; Walsh et al., 2018; Sirven, 2016; Rudzinski and Meador, 2013). This is concerning, as they are strong predictors of subjective cognitive performance, and strongly influence quality of life (Willment et al., 2015; Marino et al., 2009; Elixhauser et al., 1999; Au et al., 2006; Luoni et al., 2011; Tedrus et al., 2013). Further, impaired objective cognitive function is prevalent in PWE, with the memory domain most often affected (Marino et al., 2009). However, determining the exact influence of objective cognitive function on predicting subjective cognitive function can be difficult, and the literature at present is still greatly varied with regards to the association between the two (Marino et al., 2009; Liik et al., 2013; Tang et al., 2013; Liik et al., 2009; Karkoska et al., 2015; Giovagnoli et al., 1997). Finally, the modifying effect of mood disorders on the relationship between subjective and objective cognitive function has not yet been established.

We report the findings of a large, cross-sectional study of patients admitted for evaluation of presumed seizure disorders to an inpatient video electroencephalogram monitoring (VEM) unit to ascertain real-world data on factors predictive of subjective cognitive function. We investigate the ability of depression, anxiety, and objective cognitive function to predict subjective cognitive function, as well as describe and quantify the complex relationship and modifying effect between these factors. We also explore whether the underlying diagnosis of epilepsy or PNES affects subjective cognitive function and report other important risk factors for subjective cognitive function within this cohort.