UC Berkeley

Context: Hypersomnia is poorly defined, though evidence suggests it is associated with a range of negative health outcomes, poorer quality of life, and increased new-onset and recurrence of psychiatric illness. Lack of definition impedes generalizability across research studies.

Objective: To clarify hypersomnia diagnoses by exploring the possibility of subgroups, along with their relationship to prospective sleep data and relapse into psychiatric illness, in a sample of individuals with bipolar disorder.

Design: Prospective longitudinal analysis of a community psychiatric sample

Participants: The final sample included 159 adults (ages 18-70) with bipolar spectrum disorder diagnoses (I, II and NOS) who were euthymic at study entry.

Main Outcome Measures: Self-reports and clinician-administered interviews were used to determine features of hypersomnia, including habitual sleep duration, extent of excessive sleepiness, and napping. Participants completed sleep diaries and wore wrist actigraphy at home to obtain prospective sleep data in the home environment. Follow-up interviews were completed approximately seven months later and psychiatric status was assessed using the Structured Clinical Interview for the DSM-IV (SCID).

Results: Factor analyses confirmed two separate subtypes of hypersomnia - a group characterized by long sleep time and a group characterized by excessive daytime sleepiness - that were uncorrelated (r=-0.09). Latent profile analyses suggested a four-class solution best characterized the data, with long sleep and excessive sleepiness representing two separate classes. Prospective sleep data suggested that the sleep of `long sleepers' is characterized by long time in bed, not long sleep duration. Finally, longitudinal assessment of psychiatric illness suggested that excessive sleepiness at baseline predicted mania/hypomania relapse at follow-up.

Conclusions: This study is the largest investigation of hypersomnia to include objective measurement of sleep, and refines our understanding of classification, characterization and associated morbidity. Hypersomnia appears to be comprised of two separate subgroups, long sleep and excessive sleepiness. Long sleep is characterized primarily by long bedrest duration. Excessive sleepiness is not associated with longer sleep or bedrest, but predicts relapse to mania/hypomania. Understanding these entities has important research and treatment implications.