CHICAGO – Roughly 80% of patients with newly diagnosed and as-yet untreated acromegaly already have obstructive sleep apnea, according to the findings of what’s believed to be the largest-ever polysomnography study in such subjects.
Importantly, this study showed that the common practice of screening for sleep-disordered breathing with the Epworth Sleepiness Scale (ESS) and overnight oximetry to measure the desaturation index will greatly underdiagnose this important condition in patients with acromegaly. These are poor screening tools in this setting. They need to be supplemented by polysomnography, with the diagnosis of obstructive sleep apnea (OSA) hinging upon the finding of an abnormal apnea-hypopnea index, Dr. Andrew S. Powlson asserted at the joint meeting of the International Congress of Endocrinology and the Endocrine Society.
Dr. Powlson of the University of Cambridge (U.K.), reported on 40 consecutive patients with newly diagnosed, treatment-naive acromegaly who were evaluated by the ESS, desaturation index, and polysomnography. The study’s purpose was to shed light on a controversy: Is sleep-disordered breathing an inherent feature of acromegaly or a secondary side effect of its treatment? The question takes on added clinical relevance in light of OSA’s known predisposition to premature cardiovascular and metabolic disease, motor vehicle accidents, and impaired quality of life.
Of the 40 patients, 31 (78%) met diagnostic criteria for OSA by polysomnography. The OSA was defined on the basis of the apnea-hypopnea index as mild in 12, moderate in 5, and severe in 14.
In contrast, the ESS performed dismally as a screening instrument: Only 12 of the 31 patients with OSA had an ESS score greater than 11, which is the standard threshold for further investigation. Moreover, measurement of the diffusion index during overnight oximetry identified only 21 patients as having OSA: 11 rated mild, 7 moderate, and 3 severe, as compared to 14 patients classified as having severe OSA by polysomnography.
Patients with acromegaly displayed an increased sleep arousal index and more periodic limb movements during sleep than in reference norms, which translates into marked disruption of the normal sleep cycle. Of note, however, polysomnography showed that sleep latency – that is, the time it takes to fall asleep – and total sleep time were normal in the acromegaly patients with OSA.
Instead, the predominant pattern was one of disrupted sleep architecture. Twenty-seven acromegaly patients spent longer than expected in stage-1 sleep, while the deeper sleep stages were dramatically diminished. Indeed, 26 patients had reduced stage-2 sleep, 31 had reduced REM sleep, and 26 had shortened slow wave sleep.
Dr. Powlson reported having no financial disclosures in connection with this study, conducted with institutional funds.