Co-Morbidity and Medication Profiles of Patients with Epilepsy and Matched Controls in US and UK Electronic Health Records Systems

The global burden of epilepsy is substantial, especially in the developing regions of the world where treatments are less accessible (de Boer et al., 2008). One contribution to the overall disease burden is the higher prevalence of comorbidities among patients with epilepsy, compared to the general population. These include psychological comorbidities, such as depression, which have been associated with epilepsy, both before and after epilepsy diagnosis (Hesdorffer et al., 2005). Other neurological diseases such as migraine have also been associated with epilepsy (Ottman & Lipton, 1994). Two database studies were utilised to assess the overall comorbidity profiles of patients with epilepsy and matched controls without epilepsy. The analyses allow for comparisons between the relative prevalence estimates of comorbidities within populations captured through electronic health data sources. The US Impact National Managed Care Benchmark Database (IHCIS) is an insurance claims database provided by Ingenix, Eden Prairie, MN, and the UK General Practice Research Database (GPRD) Gold contains electronic medical records and is managed by the Medicines and Healthcare products Regulatory Agency. The IHCIS database contains medical (inpatient, outpatient, physician, and ancillary) and pharmacy claims from a national sample of 46 managed care health plans covering approximately 93 million lives over the period 1997 to 2009. The GPRD Gold is the world's largest computerised database of anonymised longitudinal medical records from primary care (Jick et al., 2003). The data are drawn from the computer systems used by general practitioners (GPs) to maintain the clinical records within their practices, and contain all records that primary care deemed relevant to patient care. Currently, data are available from 561 "research standard" general practices throughout the UK, providing information from 4.0 million currently registered patients (c. 9.0 million in total). The objectives of the current analyses were: (1) to calculate the prevalence of epilepsy diagnosis in a US and a UK electronic health record system, stratified by gender and age