But a new retrospective population-based study finds higher-than-expected frequencies of death, dementia, and arrhythmias. By Sree Roy Primary or idiopathic central sleep apnea is a disorder of unknown etiology. "Unlike other forms of central sleep apnea, our knowledge about prevalence and long-term outcomes of primary central sleep apnea is limited," says sleep specialist Ioanna Kouri, MD. Kouri, together with several Mayo Clinic colleagues, undertook a retrospective population-based study using the Rochester (Minn) Epidemiology Project resources to study patients with polysomnography-confirmed diagnosis of central sleep apnea. The journal Sleep Medicine recently published the findings. With a median followup of 4.4 years, these primary central sleep apnea patients experienced a higher-than-expected frequency of death (24%), mild cognitive impairment/dementia (20%), and cardiac arrhythmias other than heart failure with preserved ejection fraction (12%). As a retrospective look, the study may have missed existing clinical conditions not recorded at diagnosis or that were part of generalized illness not diagnosed at the time, but "it is also possible that primary central sleep apnea is having these deleterious health implications," says first author Kouri. "Sleep disturbances in patients with dementia are common and perhaps central sleep apnea can be a result of brain stem involvement. Perhaps primary central sleep apnea could be a prodromal feature of cognitive impairment or untreated central sleep apnea could have contributed to arrhythmias." Since knowledge on pathophysiology of primary central sleep apnea is limited, it's hard to explain the adverse outcomes, Kouri says. "Nevertheless this finding highlights the importance of health surveillance and bringing up any sleep concerns to the primary health provider and referring to a specialist when necessary," she says. Twenty-three of the 25 patients were started on either CPAP or adaptive servoventilation (ASV) therapy. One was on nocturnal oxygen supplementation and one declined therapy. But the frequency of adverse outcomes did not correlate with patient adherence or efficacy to positive airway pressure treatments. "However, the rarity of the disease, the study's small sample size, and its retrospective character may have contributed to this finding," Kouri says. "More studies are necessary and we should emphasize that patients should be encouraged to follow their physician’s recommendation for positive airway treatment according to the current practice parameters." In Kouri's view, firm conclusions regarding clinical significance cannot be made because of incomplete followup and the possibility of outcomes present but not reported at diagnosis. "We believe that large-scale prospective multicenter studies should be conducted in order to shed light into the clinical significance of primary central sleep apnea," Kouri says. The Mayo Clinic researchers are now studying data about opioid-induced central sleep apnea in the Rochester registry. Sree Roy is editor of Sleep Review. Reference. Kouri I, Kolla BP, Morgenthaler TI, Mansukhani MP. Frequency and outcomes of primary central sleep apnea in a population-based study. Sleep Med. April 2020;68:177-83.