Clinical significance of ADHD traits in central disorders of hypersomnolence

Attention-deficit/hyperactivity disorder (ADHD) is increasingly recognized as a potential comorbidity in central disorders of hypersomnolence (CDHs), including narcolepsy type 1 (NT1), narcolepsy type 2 (NT2), and idiopathic hypersomnia (IH). This study aimed to characterize ADHD traits within these CDH populations and evaluate their association with daily functioning. Adult participants (≥ 18 years old) with a clinical diagnosis of NT1, NT2, or IH were enrolled. Matched controls were recruited through an online platform. All participants completed validated self-report questionnaires: the Adult ADHD Self-Report Scale (ASRS), Epworth Sleepiness Scale (ESS), EuroQol 5-Dimension (EQ-5D), Kessler Psychological Distress Scale (K6), and the World Health Organization Health and Work Performance Questionnaire (WHO-HPQ). The study included 175 patients (NT1: n = 58; NT2: n = 46; IH: n = 71) and 350 controls. ADHD traits were significantly more prevalent among patients with CDH (24%) than among controls (7%), with odds ratios of 5.11 for NT1, 5.08 for NT2, and 3.87 for IH. The ADHD prevalence was not significantly different across CDH types and was predominantly inattentive. Elevated ASRS scores in CDH were not associated with increased ESS score. Among CDH patients, not ASRS but K6 was correlated with the EQ-5D score. Although ADHD traits were commonly seen in CDH, their impact on functional outcomes looked to be limited. Psychological distress driven by sleepiness in CDH is more closely related to daytime dysfunctions than ADHD traits. This may suggest the importance of prioritizing hypersomnolence management, even in patients exhibiting ADHD characteristics.