The dirty (not-so-little) secret about “clean” insomnia

Medalie et al provide an important service to the sleep community, professionals and patients alike, by reinvigorating the dialogue on the nature of chronic insomnia.¹ This vexing sleep disorder does not, probably never did, and most likely never will present without relevant comorbidities. Thinking otherwise, in our clinical experience, proves counterproductive and harmful to patients.

In our recent randomized controlled trial, substantiating the superior efficacy of adaptive servo-ventilation over continuous positive airway pressure in people with chronic insomnia with co-occurring obstructive sleep apnea/upper airway resistance syndrome (aka “complex insomnia”²), similar albeit paradoxical recruitment issues arose.³ We looked for “clean” people with insomnia who “echoed common presentations of chronic insomnia observed at mental health, primary care, and sleep clinics; none believed sleep breathing symptoms or disorders caused or contributed to their insomnia.” Further, these people with insomnia were without “obvious risks for a sleep breathing disorder: obesity, excessive daytime sleepiness, witnessed apneas, and past evaluations at sleep centers.” Yet, because so many of 660 presenting adults meeting diagnostic criteria for chronic insomnia disorder actually exhibited sleep-disordered breathing (SDB) signs or symptoms, we enrolled only 61 “clean” participants, all objectively diagnosed with obstructive sleep apnea/upper airway resistance syndrome despite the absence of SDB indicators.³

To summarize, we sought “clean” people with chronic insomnia who confidently believed they could not possibly have a sleep breathing disorder; yet, prior to randomization we excluded a huge proportion experiencing conventional SDB indicators. This pattern of presentation had been described 10 years earlier.⁴

We were surprised Medalie et al do not mention SDB as a highly relevant comorbidity.¹ The redefining of exclusion criteria, raising apnea-hypopnea index from > 10 to > 30 events/h, suggests many mild to moderate obstructive sleep apnea cases were diagnosed. With accurate upper airway resistance syndrome testing, comorbidity would be more prevalent.

More puzzling is the absence of discussion about SDB pathophysiology, given their emphasis on hyperarousal. As investigated 50 years ago by Guilleminault et al,⁵ then again more than 20 years ago^2,6 and repeatedly thereafter,⁷ SDB in insomnia is a sizeable, detectable, and treatable cause of sleep fragmentation and arousals⁸; therefore, one may ask: Why would sleep clinicians or researchers disregard this parsimonious explanation for hyperarousal? Moreover, with proper therapy, arousal activity is largely eliminated, sometimes achieving a “cure.” In our adaptive servo-ventilation wing, 68% attained “cure” status, and mean Insomnia Severity Index < 6 at endpoint (14 weeks), significantly better than continuous positive airway pressure (mean exit Insomnia Severity Index 10.19; “cure” rate 24%).³

“Guilty until proven otherwise” is the more reliable approach to SDB management among people with chronic insomnia. Regrettably, most medical and mental health clinics routinely overlook SDB in the differential diagnosis, leading to 10- to 20-year lapses prior to sleep testing,⁹ notwithstanding 50% comorbidity rates or greater.¹⁰ This substandard care causes patients unnecessary and prolonged harm from undiagnosed and untreated obstructive sleep apnea/upper airway resistance syndrome as well as creating a risk for medical malpractice among tunnel-visioned health care professionals who fail to test and diagnose complex insomnia.

I encourage Medalie et al to analyze outcomes using the essential covariate of an accurately measured respiratory disturbance index (“beyond apnea-hypopnea index”) and recommend a randomized controlled trial comparing adaptive servo-ventilation to suvorexant in light of strong directives to offer nondrug options to people with chronic insomnia.

DISCLOSURE STATEMENT

Funding source: nonprofit 501(c)(3) organization, the Sleep & Human Health Institute. Dr. Krakow reports owning websites that provide products and services for the treatment of sleep disorders and writing books describing the treatment of sleep disorders. He also provides sleep health coaching services.