Delayed Diagnosis of Narcolepsy: Family History and Clinical Features as Predictive Factors

Narcolepsy often begins in adolescence, yet diagnosis is frequently delayed. This study aimed to identify factors associated with delayed diagnosis of narcolepsy, defined as more than 1 year between symptom onset and diagnosis, focusing on age at onset, clinical symptoms, and family history.

We recruited 235 patients with clinically diagnosed narcolepsy from St.Vincent's Hospital in South Korea. Participants completed an online survey assessing age at symptom onset, diagnostic timing, clinical features, and family history of sleep disorders. Patients were classified into a non-delay group (diagnosis within 1 year, n=53) and a delay group (diagnosis after 1 year, n=182). Group differences were analyzed using independent t-tests and chi-square tests.

The mean diagnostic delay was 0.49±0.50 years in the non-delay group and 10.96±8.37 years in the delay group. The delay group had a significantly younger age at symptom onset than the non-delay group (15.13±4.88 vs. 17.89±7.91 years, p=0.002). Diagnosis in the delay group typically occurred only after marked functional impairment due to excessive daytime sleepiness. Cataplexy showed a nonsignificant trend toward earlier diagnosis, while other narcolepsy symptoms and family history were not associated with diagnostic timing.

Earlier age at onset is the strongest risk factor for delayed diagnosis of narcolepsy. Neither symptom profile nor family history reliably facilitates early recognition. Proactive screening and improved awareness among clinicians and families are needed to reduce diagnostic delay and its psychosocial burden.