The incidence of first seizures, new diagnosis of epilepsy and seizure mimics in Cork city and county during the calendar year 2017

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Maloney, Eimer M.
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University College Cork
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Introduction: Epidemiologic studies of epilepsy are necessary to define the full public health burden of epilepsy within a population and to set public health and health care priorities. Standardisation of epidemiologic methodology, detailed reporting of results and further studies from geographic regions lacking data have been called for. Furthermore, recently updated International League Against Epilepsy (ILAE) definitions of seizures and epilepsy have not been incorporated into any whole population study. Finally, no study has systematically investigated the occurrence of ‘seizure mimics’ within any population. Methods: Using multiple overlapping methods of case ascertainment, all first seizures, new diagnosis of epilepsy, and seizure mimics occuring in the defined geographical area (population 542,868 adults and children) between 1st January 2017 and 31st December 2017 were identified. Seizures and epilepsy were defined and classified according to the most recent ILAE definitions. Seizure mimics were defined as patients in whom a working diagnosis of seizure was considered, but where an alternate diagnosis was subsequently reached. An area-level relative deprivation index based on 10 indicators from census data was assigned to each patient according to address on record for the purpose of investigating the association between the incidence of each of the four diagnostic categories and relative socioeconomic deprivation. Results: The incidence of all first seizures and of seizure mimics was 102 per 100,000 (age-standardised 123) and 94 per 100,000 (age-standardised 111), respectively. When applying the 2014 ILAE definition of epilepsy, the incidence of new diagnosis of epilepsy was 62 per 100,000 (age-standardised 74) compared to 41 per 100,000 (age-standardised 48) when applying the 1993 definition, and the difference was more pronounced at older ages. The most frequently diagnosed aetiology of epilepsy was structural (54%, n=182). Almost half (n =71, 45%) of all recorded acute symptomatic seizures were related to alcohol (38%) and/or illicit drug use (n=13, 7%). The most frequently encountered seizure mimic was syncope. With regard to socioeconomic deprivation, the annual incidence of first unprovoked seizures, first provoked seizures, new diagnosis of epilepsy and seizure mimics was highest in the most deprived areas compared to the least deprived areas (incidence ratios of 1.79 (95%CI 1.26, 2.52), 1.55 (95%CI 1.04, 2.32), 1.83 (95%CI 1.28, 2.62) and 1.30 (95%CI 1.00, 1.69), respectively). Conclusions: This thesis presents the first epidemiologic study in Ireland investigating the incidence of first seizures, epilepsy and seizure mimics within the geographically defined area of Cork city and county, in accordance with international guidelines for epidemiologic studies and up-to-date international definitions and classifications of epilepsy, in order to address gaps in knowledge and to investigate the effect of updated international definitions on the epidemiologic study of epilepsy. The published results present the first international data on the effect of the updated 2014 ILAE definition of epilepsy on whole population incidence of epilepsy. Furthermore, by applying ILAE classifications to individual cases, this thesis presents detailed data on the aetiology and classification of seizures and epilepsy within the studied population. Finally, this thesis provides further support to international evidence that relatively higher socioeconomic deprivation is associated with an increased incidence of seizures and epilepsy, and presents novel data regarding the association with specific aetiologies of epilepsy and relative socioeconomic deprivation.
Epilepsy , Seizures , Incidence , Socioeconomic deprivation , Epidemiology
Maloney, E. M. 2020. The incidence of first seizures, new diagnosis of epilepsy and seizure mimics in Cork city and county during the calendar year 2017. PhD Thesis, University College Cork.
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