Epilepsy is not a very common disease compared to some other neurological diseases (e.g. like migraine). At any one time, less than one percent of Americans suffer from epilepsy. The lifetime risk of one having a defined epilepsy is probably on the order of about 5%.

The incidence of epilepsy (the number of new cases per population per year) is relatively high during the first few years of life. Risk factors for the development of childhood seizures include infection of the central nervous system, mental retardation, and cerebral palsy. Many genetic epilepsies present during early childhood.

During later childhood years and most adult years, idiopathic seizures (i.e. no cause known) predominate. Risk factors for seizures during this age include migraine, significant head injury, and central nervous system infection.

During later adult years, neurodegenerative diseases such as Alzheimer's and certain types of strokes become the most common causes of epilepsy.

Patients with epilepsy are at increased risk of sudden death. This is known as SUDEP (Sudden Unexplained Death in Epilepsy). The cause of SUDEP is not known but the risk of sudden death is several times higher in patients with epilepsy than the general population. In general, the risk of SUDEP is thought to be correlated with the severity of the epilepsy as well as with patient noncompliance. The primary event is felt to be neurological with a secondary effect on the electrical system of the heart but the exact mechanism is unclear.

Patients with epilepsy are also at higher risk for trauma in general (burns, physical injury, etc.). Seizures are usually unpredictable and many patients are unable or unwilling to take precautions against physical injury. Many patients feel their epilepsy negatively affects their quality of life. For all of these reasons, epilepsy treatment becomes of paramount importance.