Characterization of asthma comorbidity in patients with functional/dissociative seizures

INTRODUCTION: Epidemiological studies have suggested an association between asthma and functional/dissociative seizures (FDS). We compared demographic characteristics and pulmonary function test (PFT) findings in patients with FDS and comorbid asthma versus patients with asthma alone. METHOD: Patients with FDS and comorbid asthma and patients with asthma alone who had undergone PFTs were identified using ICD and CPT codes. Demographics, spirometry measures, and objective measures of asthma (bronchodilator reversibility, exhaled nitic oxide and methacholine challenge) were collected. Groups were compared using univariate and multivariate analysis. RESULTS: Patients with FDS and comorbid asthma had significantly lower FVC % predicted (p = 0.006) and fewer objective findings supportive of asthma (p = 0.017) compared with patients with asthma alone. In the multivariate analysis, the trend towards fewer objective asthma measures in patients with FDS persisted but was no longer statistically significant (OR: 0.885, 95% CI 0.755-1.037, p = 0.130), largely mediated by differences in baseline FEV1% predicted. Patients with FDS demonstrated restrictive-like findings on PFTs, potentially related to obesity and functional mechanisms such as hyperventilation. CONCLUSIONS: The association between asthma and FDS may be partially explained by overdiagnosis and symptom misattribution driven by functional respiratory mechanisms, although shared risk factors such as stressful life experiences may also contribute.