Is insomnia a breathing disorder?

1589 Editorial—Pigeon and Sateia Increased frequency of awakening is a well-documented component of chronic insomnia, but the etiology of nocturnal awakenings in these patients has received surprisingly sparse attention in sleep research. Both behavioral therapy and pharmacotherapy for insomnia are associated with self-reported decreases in number of awakenings.1 In this issue of SLEEP, Krakow and colleagues2 provide intriguing polysomnography (PSG) data about such awakenings in a group of patients whose chief complaint was chronic insomnia. The study was reported as “preliminary”; as such it involved a relatively small sample size (N = 20) and it was uncontrolled, yet the findings certainly raise important questions regarding the nature of awakenings in this population. Despite the fact that patients with clinical indicators of obstructive sleep apnea (OSA) were specifically excluded from the study sample, approximately 90% of awakenings were preceded by respiratory-related events. Most striking is that 11 of 20 participants met clinical criteria for OSA and they had a mean apnea-hypopnea index (AHI) of 14.4 (SD = 16.3); 7 others had upper airway resistance syndrome (UARS).2 Taken at face value, this suggests a sizable prevalence of occult sleep disordered breathing (SDB) among these patients who had treatment-resistant chronic insomnia. The sample studied by Krakow et al.2 was typical of chronic insomnia populations, endorsing high subjective ratings of insomnia severity, long duration of insomnia, normal BMI, high levels of comorbidity, and being predominantly female. However, three quarters of the sample was also taking sleep medications nightly, half had a trauma history, and 55% snored (the precise basis for exclusion on the basis of breathing-related symptoms is not specified). One or more of these characteristics could contribute to the observed occurrence of SDB or to awakenings. Moreover, since arousal can predispose individuals to ventilatory instability including upper airway instability,3-5 a testable question arises about the sequencing of arousal and respiratory events. Namely, does heightened tonic arousal/sympathetic activation or phasic cortical/subcortical arousal result in destabiEDITORIAL