Insomnia subtypes and their relationships to daytime sleepiness in patients with obstructive sleep apnea

BACKGROUND: Insomnia and obstructive sleep apnea syndrome (OSA) are the two most common sleep disorders. Studies showed that insomnia complaints were prevalent in OSA. Relatively little is known about the causes of insomnia in OSA and whether etiological factors differ for insomnia subtypes. We hypothesized that sleep onset problem was mainly due to hyperarousal and sleep maintenance difficulty was primarily related to sleep-disordered breathing. OBJECTIVES: To determine the prevalence of insomnia subtypes in OSA, compare subjects with sleep onset insomnia, sleep maintenance insomnia and no insomnia symptom, and study the relationship of insomnia subtypes to daytime sleepiness. METHODS: We analyzed intake questionnaires and polysomnography and Multiple Sleep Latency Test results of 157 OSA patients. RESULTS: Forty-two percent of the sample had at least one problematic insomnia symptom. The prevalence of sleep onset insomnia, sleep maintenance insomnia and insomnia with early awakening was 6, 26 and 19%, respectively. Patients with sleep onset insomnia had significantly lower apnea-hypopnea (AHI) and arousal indices. There were significant inverse relationships between sleep onset insomnia and measures of daytime sleepiness. On the contrary, subjects with repeated wakening had more severe subjective sleepiness. Results were similar in patients with AHI >or=5 or >or=15. CONCLUSIONS: Insomnia symptoms were common in OSA patients. Insomnia subtypes related differently to measures of daytime sleepiness. Our findings suggest that OSA patients with sleep onset insomnia may be in a state of hyperarousal. It is clinically relevant to examine insomnia subtypes, which may influence the treatment decision in sleep-disordered breathing.