0706 Clinical and Psychiatric Predictors of Objective Sleep Latency in Idiopathic Hypersomnia and Related Disorders: A Retrospective Cohort Analysis

Abstract Introduction Idiopathic hypersomnia (IH) and other central hypersomnolence disorders present diagnostic challenges due to heterogeneous symptoms, psychiatric comorbidities, and wide variability in patients’ sleep patterns. Understanding predictors of sleep latency may improve diagnostic precision and help distinguish hypersomnolence from circadian or psychiatric contributors. This study examined demographic, psychiatric, behavioral, and sleep-related factors associated with mean sleep latency in a real-world clinical cohort. Methods We conducted a retrospective analysis of adult patients who underwent multiple sleep latency testing (MSLT) for hypersomnolence evaluation between January 2000 and May 2025 at a tertiary sleep center in Lansing, Michigan. We excluded patients with untreated or inadequately treated obstructive sleep apnea (residual apnea-hypopnea index (AHI) >5/hours)) and those with total sleep time < 6 hours on the preceding night. The study was approved by the Michigan State University Institutional Review Board. Descriptive statistics were generated for demographic, clinical, and polysomnographic variables. Multivariable linear regression was used to identify predictors of mean sleep latency. Results Participants were predominantly female (76.7%), Caucasian (83.7%), and employed (67.4%). Mean age was 36.4 ± 14.2 years, BMI 28.3 ± 6.9 kg/m², sleep latency 8.7 ± 4.2 minutes, and total sleep time 402 ± 28 minutes. Idiopathic hypersomnia was present in 95.4% of the cohort, and 4.7% had narcolepsy. Psychiatric comorbidities were common, including major depression (52%), anxiety (53.5%), and dysthymia (23.3%). Circadian rhythm disorder was associated with an average 6.8-minute increase in sleep latency (95% CI: 2.68–10.94; p = 0.02). Central hypersomnolence disorders showed a non-significant trend toward shorter latency (–6 minutes; p = 0.13), consistent with expected patterns in narcolepsy-spectrum presentations. No meaningful associations were found for age, sex, BMI, depression, anxiety, attention deficit hyperactivity disorder, cataplexy, or alcohol/drug use. Conclusion Circadian rhythm disorder was the strongest predictor of prolonged sleep latency, underscoring the importance of evaluating circadian misalignment when interpreting MSLT results in suspected IH. The substantial psychiatric burden observed underscores the importance of concurrent mental health assessment. Overall, the results point to specific clinical characteristics that may help clinicians differentiate sleepiness related to IH, narcolepsy-spectrum symptoms, and circadian rhythm problems. Support (if any)