The epidemiology of drug-resistant epilepsy: A systematic review and meta-analysis.

Objective: The definition of drug-resistant epilepsy (DRE) affects case identification and treatment, and impacts prevalence or incidence estimates and health burden estimation in epidemiology. The objective of this systematic review is to evaluate the consistency between definitions of DRE in the literature and the official definition in the International League Against Epilepsy (ILAE) guidelines, and to estimate the incidence, prevalence, and risk factors for DRE.

Methods: MEDLINE and EMBASE were searched for observational studies of DRE published between January 1980 and July 2015. The definitions of DRE in these studies were compared with the definition in the ILAE guidelines. Random-effect model meta-analyses were used to generate pooled estimates of prevalence or incidence and pooled odds ratios of the association with risk factors.

Results: Thirty-five studies met inclusion criteria, including 13 080 epilepsy patients and 3941 patients with DRE. The definition of DRE varied widely across studies, with only 12% meeting the requirements of the ILAE definition. The pooled prevalence proportion of DRE among epilepsy patients was 0.30 (95% confidence interval [CI] 0.19-0.42), and the pooled incidence proportion was 0.15 (95% CI 0.11-0.19). Age at onset, symptomatic epilepsy, abnormal neuroimaging findings, abnormal electroencephalography results, history of mental retardation, neuropsychiatric disorders, febrile seizure, and status epilepticus increased risk for DRE.

Significance: There are limited high-quality data available on DRE. Lack of consistency in definitions limits the ability to obtain robust estimates on the burden of DRE. More data based on the ILAE definition from well-designed epidemiologic studies are needed to generate accurate and reliable results.