Prevalence of epilepsy--an unknown quantity.
The incidence, prevalence, and mortality of epilepsy vary across countries with different economies. Differences can be explained by methodological problems, premature mortality, seizure remission, socioeconomic factors, and stigma. Diagnostic misclassification-one possible explanation-may result from inclusion of patients with acute symptomatic or isolated unprovoked seizures. Other sources of bias include age and ethnic origin of the target population, definitions of epilepsy, retrospective versus prospective ascertainment, sources of cases, and experienced and perceived stigma. Premature mortality is an issue in low-income countries (LICs), where treatment gap, brain infections, and traumatic brain injuries are more common than in high-income countries (HICs). Death rates may reflect untreated continued seizures or inclusion of acute symptomatic seizures. Lack of compliance with antiepileptic drugs has been associated with increased risk for death, increased hospital admissions, motor vehicle accidents, and fractures in poor communities. Epilepsy is a self-remitting clinical condition in up to 50% of cases. Studies in untreated individuals from LICs have shown that the proportion of remissions overlaps that of countries where patients receive treatment. When the identification of patients is based on spontaneous reports (e.g., door-to-door surveys), patients in remission may be less likely to disclose the disease for fear of stigmatization with no concurrent benefits. This might lead to underascertainment of cases when assessing the lifetime prevalence of epilepsy. In LICs, the proportion of people living in poverty is greater than in HICs. Poverty is associated with risk factors for epilepsy, risk for developing epilepsy, and increased mortality. The high incidence and prevalence of epilepsy found in LICs is also observed in low income individuals from HICs. Epileptogenic conditions are associated with an increased mortality. This may partly explain the difference between incidence and lifetime prevalence of epilepsy in LICs. Poverty within LICs and HICs could be a preventable cause of mortality in epilepsy.