Comorbidities in patients with epilepsy: Frequency, mechanisms and effects on long-term outcome.

OBJECTIVE: To assess frequency, types, and mechanisms of comorbidities in people with epilepsy and verify their association with disease features and outcome. METHODS: This cohort study was performed in 13 Italian epilepsy centers with nationwide distribution and accurate records. Eligible patients were children and adults diagnosed before December 31, 2005, and followed for a minimum of 10 years. Two pairs of raters independently reviewed patients' records and classified each comorbidity. In case of disagreement, a third reviewer made the final decision. Comorbidities were classified according to type (organ/system) and underlying mechanism (causal, shared risk factors, chance association). Comorbidity types and mechanisms were described in the entire sample and according to epilepsy prognostic patterns (sustained remission, relapsing-remitting course, no remission). RESULTS: Of 1006 included patients, 266 (26.4%) had at least one comorbidity. The most common were developmental/perinatal (7.5% of cases), psychiatric (6.2%), cardiovascular (5.3%), and endocrine/metabolic (3.8%). Among 408 reported comorbidities, the underlying mechanisms were, in decreasing order, chance association (42.2%), shared risk factors (31.1%), and causal (26.7%). Psychiatric diseases were present in 13.3% of patients with no remission, 5.9% of patients with relapsing-remitting course, and 4.8% of patients with sustained remission (p = .016). The corresponding numbers for endocrine/metabolic diseases were respectively, 9.6%, 3.4%, and 2.9% (p = .013); for respiratory diseases were 3.6%, .3%, and .3% (p = .001), and for urogenital diseases were 3.6%, .7%, and 1.6% (p = .048). The association of endocrine/metabolic, psychiatric, and respiratory comorbidities with epilepsy prognosis was confirmed by multivariable analysis adjusted for the main demographic and clinical variables, with patients with these comorbidities showing a lower probability of achieving remission. SIGNIFICANCE: Comorbidities in epilepsy are not uncommon and reflect differing underlying mechanisms. Psychiatric, endocrine/metabolic, and respiratory disorders are associated with a worse long-term epileptological outcome.