The Comorbidities of Epilepsy

By Marco Mula

Epilepsy is one of most frequent neurological disorders affecting about 50 million people worldwide and 50% of them have at least another medical problem in comorbidity; sometimes this is a the cause of the epilepsy itself or it is due to shared neurobiological links between epilepsy and other medical conditions; other times it is a long-term consequence of the antiepileptic drug treatment.

The Comorbidities of Epilepsy offers an up-to-date, comprehensive overview of all comorbidities of epilepsy (somatic, neurological and behavioral), by international authorities in the field of clinical epileptology, with an emphasis on epidemiology, pathophysiology, diagnosis and management. This book includes also a critical appraisal of the methodological aspects and limitations of current research on this field. Pharmacological issues in the management of comorbidities are discussed, providing information on drug dosages, side effects and interactions, in order to enable the reader to manage these patients safely.

The Comorbidities of Epilepsy is aimed at all health professionals dealing with people with epilepsy including neurologists, epileptologists, psychiatrists, clinical psychologists, epilepsy specialist nurses and clinical researchers.

• Provides a comprehensive overview of somatic, neurological and behavioral co-morbidities of epilepsy
• Discusses up-to-date management of comorbidities of epilepsy
• Written by a group of international experts in the field

• Language: English
• Publisher: Academic Press
• Release date: Apr 20, 2019
• ISBN: 9780128148785

Book preview

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Preface

Marco Mula, Institute of Medical and Biomedical Education, St George’s University of London and the Atkinson Morley Regional Neuroscience Centre, St George’s University Hospitals NHS Foundation Trust, London, United Kingdom

Epilepsy is one of the most frequent neurological disorders affecting about 50 million people worldwide. In 1970, Alvin Feinstein defined as comorbidity any distinct additional clinical entity that existed during the clinical course of a patient who has the index disease. The practical definition of epilepsy issued by the International League Against Epilepsy in 2014 explicitly recognizes the neurobiological, cognitive, psychological, and social consequences of epilepsy. However, in addition to that, it is becoming evident that patients with epilepsy present with a number of medical problems as a result of the epilepsy itself or because the epilepsy shares some biological links with other medical conditions or as a long-term consequence of the antiepileptic drug treatment.

During the last 15 years, a number of studies have focused on the issue of comorbidities of epilepsy, showing that some disorders are indeed more frequently encountered among patients with epilepsy as compared to the general population. These findings have led to several hypotheses about a shared pathophysiology between epilepsy and these conditions, stimulating research in this area and emphasizing the importance of recognizing this specific group of comorbidities. In fact, although seizure freedom always remains the main goal of the treatment of epilepsy, comorbidities represent an important predictor of quality of life, especially in those patients where seizure freedom is not sustained. But even in those who are in full remission, if comorbidities are not addressed or seizure freedom is achieved at the expense of unacceptable long-term complications, adherence and quality of life remain poor.

For many years, epileptology remained a highly specialized subspecialty focusing on a limited number of technical issues like intracranial monitoring for epilepsy surgery or genetic and advanced neuroimaging techniques. Health professionals are now realizing the importance of comorbidities in patients with epilepsy and the key role of epilepsy centers in addressing these problems in the context of a holistic approach to epilepsy care. This book represents an up-to-date overview of the comorbidities of epilepsy (somatic, neurological, and behavioral), by active international authorities in the field of clinical epileptology, with an emphasis on epidemiology, pathophysiology, diagnosis and management. The book discusses also the problem of comorbidities from a public health point of view and provides the point of view of epilepsy specialist nurses whose role is invaluable in managing complex patients with multiple chronic conditions. This book has a strong clinical perspective and it has been written by clinicians for clinicians with the aim of improving epilepsy care and quality of life of our patients.

Chapter 1

The comorbidities of epilepsy: A conceptual framework

Daniel Navin Olschewski⁎; Prisca R. Bauer†; Josemir W. Sander‡,§,¶    ⁎ Department of Neurology, University Hospital of Cologne, Cologne, Germany

† Lyon Neuroscience Research Center, Brain Dynamics and Cognition Team, INSERM UMRS 1028, CNRS UMR 5292, Université Claude Bernard Lyon 1, Université de Lyon, Lyon, France

‡ NIHR University College London Hospitals Biomedical Research Centre, UCL Queen Square Institute of Neurology, London, United Kingdom

§ Chalfont Centre for Epilepsy, Chalfont St Peter, United Kingdom

¶ Stichting Epilepsie Instellingen Nederland (SEIN), Heemstede, Netherlands

Abstract

Over 50% of people with epilepsy have one or more somatic or psychiatric conditions. Five mechanisms of association are identified: conditions that cause epilepsy (causative); conditions caused by epilepsy (resultant); conditions that share the same risk factors as epilepsy, conditions that link epilepsy and other conditions; conditions that can be caused by epilepsy and vice versa (bidirectional); and lastly, artifactual associations between epilepsy and other conditions. Comorbidities have consequences for the diagnosis and prognosis of epilepsy and negatively impact quality of life and health care-related costs. Epilepsy is thus not a stand-alone condition but a symptom of systemic dysfunction requiring appropriate diagnosis and treatment of all associated symptoms and conditions.

Keywords

Epilepsy; Co-morbidity; Risk factor; Genetics; Inflammation; Oxidative stress; Mitochondrial dysfunction; Glycation; Methylation

Contents

1.Mechanisms of association between epilepsy and comorbid conditions

1.1Causative

1.2Resultant

1.3Shared risk

1.4Genetics

1.5Bidirectional

1.6Chance, artifactual, or spurious association

2.The burden of comorbidity

2.1Diagnosis

2.2Treatment

2.3Quality of life

2.4Mortality

2.5Costs

3.Epilepsy as a systemic condition

References

Abbreviations

AED’s 

antiepileptic drugs

ICD 

International Classification of Diseases

ILAE 

International League Against Epilepsy

QOLIE-10 

quality of life in epilepsy questionnaire

SCN1A 

gene that codes for the alpha subunit of the voltage-gated sodium ion channel

SUDEP 

sudden unexpected death in epilepsy

Epilepsy, a relatively common neurological condition, is a complex symptom that rarely stands alone. Several large population-based studies have shown that up to 50% of people with epilepsy also have a comorbid condition [1, 2]. In epilepsy, comorbidity implies the coexistence of other medical conditions preceding, co-occurring with, or following the diagnosis of epilepsy, related or unrelated to the underlying potential or putative cause of epilepsy.

The comorbidities of epilepsy encompass somatic and psychiatric conditions, and the prevalence of some of them is up to eight times higher in people with epilepsy than in the general population [3–5]. The comorbidities may impact the diagnosis of epilepsy mainly due to issues of attributions. They can influence treatment decisions as often the choice of antiepileptic medications may positively or negatively affect the comorbid condition, thus complicating a holistic approach to the management of the individual. Comorbidities also affect quality of life and prognosis and result in more frequent visits to health professionals and higher health care-related costs [6].

This chapter provides a theoretical framework for the comorbid associations of epilepsy. It should be seen as a foreword for this topical book on the comorbidities associated with epilepsy, which are responsible for a significant part of the burden epilepsy imposes on the individual and society. It also provides a brief overview of the different potential mechanisms of association between epilepsy and comorbidities and of some recent pathophysiological evidence, which may explain some associations. Most of the comorbid associations of epilepsy mentioned in this chapter will be discussed in more detail in other chapters.

1 Mechanisms of association between epilepsy and comorbid conditions

The comorbidities associated with epilepsy can be subdivided by affected organ system and the International Classification of Diseases [4, 5]. Based on the current understanding of disease mechanisms and temporal associations, epilepsy-associated comorbid conditions can also be divided into five mechanist categories. This type of categorization was initially conceptualized for the classification of migraine and associated comorbid disorders [7]. The categories are: causative mechanisms; resultant mechanisms; shared risk factors; bidirectional effects; and chance and artifactual comorbidities [4, 5]. Table 1 summarizes conditions associated with epilepsy.

Table 1

1.1 Causative

Some medical conditions can result in epilepsy. This causative relationship is the most straight-forward mechanism of association; for example, stroke, traumatic head injury, and neoplasms are included among the most common causes of symptomatic epilepsy [4]. Some conditions, such as brain tumors [8], alcohol dependence [10], multiple sclerosis [11–13], and cerebrovascular disease [9], seem to have a direct cause-and-effect association with epilepsy, whereas risk factors for cardiovascular and cerebrovascular diseases and brain metastases increase the risk of developing epilepsy indirectly [14, 15].

1.2 Resultant

Some conditions can be caused by epilepsy. This category includes the effects of antiepileptic drugs (AEDs) and other medication used in epilepsy [4]. AEDs, particularly enzyme inducers, may play a pivotal role in this mechanism of association and can lead to impaired bone health and density [16, 17]. Consequences of seizures include fractures [18], aspiration pneumonia [3], headache [19] and urinary incontinence [20].

1.3 Shared risk

A shared risk factor is one underlying factor or condition, which results in the development of two or more distinct conditions. The shared risk factor can be of environmental, genetic, neurochemical, physiological, or structural origin [4]. For example, it has been suggested that the co-occurrence of diabetes mellitus type I and some types of temporal lobe epilepsy is mediated through the presence of the anti-glutamic acid decarboxylase (GAD) antibody [23]. Other biological and structural shared risk factors have also been suggested for systematic lupus erythematosus [22] and dementia [21, 25, 26]. Different forms of migraine and epilepsy may be caused by environmental, biological or genetic shared risk factors [4, 19, 27, 28].

1.4 Genetics

Genetic factors can impact the relationship between epilepsy and comorbidities in various ways. They can be either the basis for developing epilepsy or a comorbidity or the source of a shared risk factor for epilepsy and a comorbidity. For instance, mutations in SCN1A, a gene that codes for the alpha subunit of the voltage-gated sodium ion channel, can result in the development of Dravet syndrome (severe myoclonic epilepsy in infancy), as well as a motor disorder [24]. Genetic factors also influence the association between epilepsy and comorbidities [41]. For example, carriers of the APOE e4 allele seem to be at greater risk of developing epilepsy after traumatic brain injury [29]. Genetic predisposition may therefore play an important role in the clustering of comorbid conditions and understanding of these may be of vital importance for a holistic person-centered management approach.

1.5 Bidirectional

A bidirectional, or reciprocal, association arises when one condition can cause another condition and vice versa. These two conditions do not have a strict temporal sequence, meaning that either does not have to precede the other, as could similarly be the case for a shared risk factor. Rather, it involves a complex relationship between two conditions through pathophysiology, genetics, and environment [5]. Bidirectional association with epilepsy has been suggested for depression, anxiety, psychosis, autism spectrum disorder, migraine, and attention deficit and hyperactivity disorder [30–35].

1.6 Chance, artifactual, or spurious association

For some conditions, the frequency of prevalence or incidence in people with epilepsy is the same as in the general population [42]. Information or selection bias can lead to wrongfully attributed links between epilepsy and other conditions [42].

Selection bias is a result of a false representation of the general population in the study population, leading to a misleading relationship between conditions. This includes referral, non-response, and publication bias [42–44]. For example, arthritis [36], chronic fatigue [37, 38], asthma [39, 40], peptic ulcers, and gastrointestinal bleeding [3] may have an artifactual association with epilepsy.

2 The burden of comorbidity

2.1 Diagnosis

Understanding the association between epilepsy and other conditions is necessary to improve care for people with epilepsy [39, 45]. A positive diagnosis of epilepsy should always increase the suspicion that other disorders, either psychiatric or somatic, may be present as it often causes conditions in both domains. Cognitive, psychiatric, and somatic comorbidities are frequently underdiagnosed and undertreated in people with epilepsy [17, 46, 47]. It is important to diagnose and treat comorbidities as early as possible [48]. Regular screening of people with epilepsy for comorbidities, similar to screening for conditions such as depression and osteoporosis in the general population, is therefore important [5, 48].

An important driver for holistic epilepsy care should be the identification and appropriate diagnosis of comorbidities as often assessments in the epilepsy clinic are mostly about seizure control. Screening tools specifically for comorbidities in epilepsy are yet to be developed and implemented.

2.2 Treatment

Comorbidities can strongly influence treatment and outcomes. When treating epilepsy and comorbidities, ideally, a treatment targeting both should be selected. For example, people with migraine and epilepsy might benefit from treatment with topiramate whereas lamotrigine may be the preferred choice for people with epilepsy and a mood disorder [49, 50]. Conversely, some AEDs have a negative effect on certain conditions. The AED perampanel was shown to induce psychiatric adverse reactions in individuals with epilepsy and psychiatric comorbidities [51]. The presence of conditions such as migraine or psychiatric conditions was shown to be associated with a higher risk of pharmacoresistance in people with epilepsy [52].

2.3 Quality of life

The presence of comorbid conditions in people with epilepsy is associated with reduced quality of life [39]. More than half of people with epilepsy and comorbid depression had a reduction in quality of life as measured with the Quality of Life in Epilepsy-10 questionnaire [53]. Depression and attention deficit hyperactivity disorder are important predictors of quality of life, independently from epilepsy and its severity [54]. The primary goal should be seizure freedom, as people who are seizure-free have the same quality of life as the general population, but the prevention and targeted treatment of comorbidities is also necessary to restore quality of life [39, 55].

2.4 Mortality

People with epilepsy have a two- to threefold overall increase in premature mortality rates compared with the general population [56, 57]. Premature mortality risk is highest soon after the first seizures, and it remains elevated even after seizure freedom and off antiepileptic medication [58, 59]. This continuing risk of increased mortality, which seems independent of seizure and drug treatment, is most likely multifactorial, but it is likely that comorbidities play an important role on this. This requires further investigations.

Sudden unexpected death in epilepsy (SUDEP) is the most common cause of epilepsy-related death, it accounts for an estimated 4% of deaths in low-risk groups of people with epilepsy [37, 60]. People who have had a single seizure are attributed to the low-risk group [61]. It is possible that SUDEP shares some commonality with the so-called sudden adult death, and this also requires further investigation.

In people with symptomatic seizures, the majority of deaths within the first year of epilepsy onset are due to the underlying condition rather than the seizures themselves [62]. Most deaths are due to somatic comorbidities, such as cardiovascular or cerebrovascular disease, malignancies, or pneumonia, which are more likely to occur in people with epilepsy than in the general population [58]. Underlying depression and substance abuse in people with epilepsy also lead to increased mortality through suicide [63]. Whether AEDs also have an impact on suicidal behavior in people with epilepsy remains a matter of debate [64].

2.5 Costs

Direct medical costs in people with epilepsy are largely (80%) related to comorbidities rather than to epilepsy [65]. The risk of admission to a hospital is increased, and the medical costs are almost 50% higher than for people with epilepsy without comorbidities [66].

Consequently, early detection and intervention may also result in lower medical costs for those affected.

3 Epilepsy as a systemic condition

The increased prevalence of comorbidities and lifelong elevated risk of premature mortality in people with epilepsy suggest that there might be an underlying systemic dysfunction in some cases [67]. Systemic dysfunction may be a shared risk factor, resulting in the observed associations with other conditions [67].

Through the implementation of validated screening instruments, comorbidities might serve as indicators and prognostic factors for the course of the disease. Developments in this direction are already apparent: comorbidities, such as learning difficulties and psychiatric conditions, were included in the revised classification scheme of epilepsy by the International League Against Epilepsy in 2017 in order to ensure a holistic approach to patient care [68].

In the future, a better understanding of the association between epilepsy and other conditions might make targeted person-centered therapy possible. Therefore, more research in the pathophysiological mechanisms described in this chapter is warranted. Indeed, it could be argued that an important part of all future phenotypic stratification in epilepsy should be the identification of comorbidities as clustering of these could provide insight into common mechanisms, particularly common genetic predispositions.

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Chapter 2

Costs of epilepsy: The impact of comorbidities

Churl-Su Kwon⁎,†; Charles E. Begley‡; Nathalie Jetté⁎,†    ⁎ Department of Neurology, Icahn School of Medicine at Mount Sinai, New York, NY, United States

† Department of Population Health Science and Policy, Icahn School of Medicine at Mount Sinai, New York, NY, United States

‡ Center for Health Services Research, School of Public Health, University of Texas Sciences Center, Houston, TX, United States

Abstract

Although there have been many studies looking into the cost of epilepsy in the general epilepsy population, studies examining the impact of comorbidities on epilepsy costs are scarce. Further, there have not been any studies evaluating the potential impact of preventing or treating comorbidity in epilepsy (e.g., medical, neurological, or psychiatric) from a public health perspective. This chapter will review basic concepts of cost of illness in epilepsy and the impact of comorbidities on the cost of epilepsy.

Keywords

Epilepsy; Comorbidities; Cost and cost analysis; Cost of illness; Economic burden

Contents

1.Introduction

2.How is cost measured?

2.1Direct cost

2.2Indirect and social service cost

3.Existing cost estimates

3.1Direct costs of epilepsy

3.2Indirect costs of epilepsy

3.3Intangible costs of epilepsy

4.How do comorbidities influence the cost of epilepsy?

5.Gaps in care and knowledge

References

Abbreviations

AED 

antiepileptic drug

COI 

cost of illness

ILAE 

International League Against Epilepsy

PPP-US$ 

United States Dollar purchasing power parities

QOLIE-10 

quality of life in epilepsy inventory-10

1 Introduction

Epilepsy is the second most common neurological disorder estimated to affect 50 million people worldwide [1]. A recent systematic review and meta-analysis of international studies reported a lifetime epilepsy prevalence of 7.60 per 1000 persons (95% CI 6.17–9.38) and an incidence rate of 61.44 per 100,000 person-years (95% CI 50.75–74.38) [2]. Epilepsy has serious health consequences and is associated with increased medical and social service costs and decreased productivity in patients globally [3]. Previous research has recognized the global burden of epilepsy in low- and high-resource countries, enhancing our understanding of the relationship between the economic burden of epilepsy and its epidemiology, somatic/psychiatric comorbidities, stigma, and health policy [3–9].

In the United States total direct and indirect epilepsy cost estimates have ranged from $9.6 billion (2004 dollar) to $12.5 billion (1995 dollar) annually [10]. The estimated cost of epilepsy in Europe in 2004 was €15.5 billion [11]. A recent systematic review of cost of illness (COI) epilepsy studies noted that the direct average annual medical costs related to epilepsy ranged from 40 international United States Dollar purchasing power parities (PPP-US$) in a low-resource country to PPP-US$4748 in a high-resource country [12]. This estimate does not account for all direct expenses in epilepsy nor the indirect costs that can represent up to 85% of the overall cost [12]. The drivers of the direct costs of epilepsy care are multifaceted. Making a diagnosis of epilepsy can involve multiple tests and procedures, medical management, and multiple drugs, and the work-up for and provision of surgery and/or other alternative therapies for more severe epilepsy are cost-intensive [13]. Mean direct medical costs are seen to decrease nearly eightfold within a four-year period from diagnosis, once seizure control is achieved [13]. Health care costs have been shown to decline after successful epilepsy surgery [14].

International cost comparisons are difficult due to disparities in the treatment gap, which has been estimated to result in no treatment or undertreatment of 90% of individuals with epilepsy in some countries [12, 15, 16]. In 2002, as a result of the incongruity between COI studies, the International League Against Epilepsy Commission on the Burden of Epilepsy, Subcommission on the Economic Burden of Epilepsy, published a report providing methodological recommendations for economic analyses in epilepsy [17]. The following were suggested: (1) COI studies should be population-based; (2) studies need to be conducted prospectively; (3) retrospective studies are of value, and need to be population-based rather than focused on subsets of these cohorts; (4) economic analyses studies must be comprehensive, including both direct and indirect costs that can be attributed to epilepsy.

The emphasis on cost control and managed care in health care delivery has increased our awareness of the importance of economic evaluations in epilepsy. COI analysis encompasses various aspects of disease impact on health outcomes for the individual patient, the health care system, and the country as a whole. COI may focus on the longitudinal effects of the disease on morbidity, mortality, and quality of life from onset, or the annual effects of the disease across prevalent cases. Estimating COI is important to help prioritize medical and social service decisions of patients and providers and inform health policymakers in determining appropriate allocation of funds. It has been consistently found that patients with epilepsy have a higher prevalence of somatic and psychiatric comorbidities as compared to those without epilepsy and that they often experience health and social disparities, reduced quality of life, and poorer socioeconomic status [18–21].

Comorbidities associated with epilepsy and their inclusion/exclusion in cost of epilepsy studies explain some of the discrepancies between cost studies due to their influence on the need for services and functioning of people living with epilepsy. Although there have been many studies examining the cost of epilepsy, there are only a few evaluating the impact of comorbidities (medical, neurological, and psychiatric) and the potential impact of prevention strategies from a public health perspective on the cost of epilepsy. In this chapter, we review some basic concepts of COI in epilepsy and the impact of comorbidities on the cost of epilepsy.

2 How is cost measured?

Epilepsy COI studies are challenging as ideally they should consider the direct, indirect, and intangible costs from various perspectives (i.e., the individual, caregivers, third-party payers, and societal perspective) [22]. COI studies that incorporate direct, indirect, and intangible costs are rare. Most research has focused on direct costs and even when indirect and intangible costs are addressed, the components analyzed within studies vary. COI studies are also heterogeneous due to differing geographic regions and health care systems, which subsequently leads to contrasting health care costs between studies. Even studies that are performed in the same country report widely varied epilepsy cost estimates [4, 23, 24]. For example, in the United Kingdom, Swingler et al. [23] looked at patients attending a specialist epilepsy service while Cockerall et al. [4] and Jacoby et al. [24] focused on community-based studies. Thus, comparisons across studies are incredibly difficult, especially when there is a gap in knowledge about overall health resource utilization. Also, most lifetime COI studies are based on statistical modeling since rigorous prospective cohort studies are challenging and costly to perform.

2.1 Direct cost

Direct cost of epilepsy care refers to spending on medical and social services utilized in diagnosing, treating, rehabilitating, and preventing disability. This encompasses outpatient visits, hospitalizations, investigations, medical, surgical, and other alternative therapies, residential care, and so forth. The costs of medical services are typically reported as the average payments made to health care providers and/or facilities. Estimates of direct cost may vary if reported from the patient's (out-of-pocket payments at point of service) or insurance company's (payment for services covered by the plan) point of view. In the United States, patients enrolled in government-funded plans (Medicare for the elderly and disabled, and Medicaid for low-income and disabled) generally incur less out-of-pocket costs than those with private insurance. Most COI studies investigate cost using a payer's point of view because of the availability of