Psychiatric and neurologic risk factors for incident cases of new-onset epilepsy in older adults: Data from US Medicare beneficiaries

Objective: Neurologic diseases such as stroke are risk factors for new-onset epilepsy in older adults. Recent evidence suggests that psychiatric disorders independently predict epilepsy in older male veterans. Our aim was to examine the relationship between these disorders in a population-based study of older adults that also included women and minorities. Methods: Weused a national 5% random sample of 2005 Medicare beneficiaries including all 50 US states and Washington, DC. Beneficiaries were 65 years of age or older, with continuous Medicare Part A and Part B coverage and not in managed care plans. Epilepsy cases were identified from claims for physician visits, hospitalizations, and outpatient procedures. We used logistic regressions for the overall sample and stratified by gender to determine whether risk of new-onset epilepsy was associated with prior history of psychiatric (i.e., depression, psychosis, bipolar disorder, schizophrenia, posttraumatic stress disorder (PTSD), adjustment disorder, and substance abuse/dependence) and neurologic conditions (i.e., cerebrovascular disease, dementia, traumatic brain injury, brain tumor, metastatic cancer). Results: Preexisting psychiatric disorders were significantly associated with new-onset epilepsy in the study population as were the neurologic conditions evaluated. Five of the seven psychiatric disorders examined were independently associated with new-onset epilepsy; substance abuse, psychosis, bipolar disorder, schizophrenia, and depression. Gender interaction effects were found for substance abuse/dependence and brain tumors. Significance: Both neurologic and psychiatric factors significantly predicted new-onset epilepsy in a population-based sample of male and female older adults. These results support earlier findings and extend the understanding of risk models for new-onset epilepsy in broader older adult populations.