A high prevalence of mild cognitive impairment has been reported in patients referred to sleep clinics for suspected obstructive sleep apnea (OSA), according to results of an analysis published in the Annals of the American Thoracic Society.
Investigators sought to establish the prevalence of mild cognitive impairment in a population of individuals referred to 1 of 3 academic sleep centers for suspected OSA and to determine who may be at the highest risk for development of mild cognitive impairment. A total of 1084 participants (age range, 18-80) who were recruited from July 2016 to February 2019 were enrolled in the multicenter Canadian Sleep and Circadian Network adult OSA database. These individuals had been referred for suspected OSA, or had a known diagnosis of OSA without having received any treatment for at least 6 months. The presence of OSA had been diagnosed by unattended, home sleep apnea testing or in-laboratory polysomnography. All participants completed sleep and medical history questionnaires, the Montreal Cognitive Assessment Test (MoCA) of Global Cognition, the Rey Auditory Verbal Learning Test of Memory, and the Wechsler Adult Intelligence Scale-Fourth Edition (WAIS-IV) Digit-Symbol Coding (DSC) subtest of information processing speed.
A MoCA score of less than 26 (range, 0-30) was defined as having mild cognitive impairment. Overall, the presence of mild cognitive impairment was reported in 47.9% of the entire patient cohort, which increased to more than 55.3% in those with moderate and severe OSA. Findings showed that patients with a MoCA score of less than 26 were mainly older men who had more severe OSA, hypoxemia, and vascular comorbidities.
Compared with patients with no OSA, the presence of moderate and severe OSA was independently associated with a more than 70% higher likelihood for mild cognitive impairment (P =.003). Additionally, the memory and information processing speed was significantly lower in the entire patient cohort compared with age-matched normal values (P <.001). In fact, lower DSC and MoCA scores were linked to a higher oxygen desaturation index and nocturnal hypoxemia.
The investigators concluded that moderate to severe OSA is an independent risk factor for mild cognitive impairment. Based on the study findings, it has been suggested that older patients with more severe OSA, nocturnal hypoxemia, and vascular comorbidities who are at the highest risk for mild cognitive impairment should be triaged to receive more definitive OSA therapy, with greater attention to and support for continuous airway pressure (CPAP) adherence. Additional research is warranted, however, to determine whether such an approach will be feasible and effective for decreasing the number of patients with OSA who progress from mild cognitive impairment to dementia.
Beaudin AE, Raneri JK, Ayas NT, et al; on behalf of the Canadian Sleep and Circadian Network (CSCN). Cognitive function in a sleep clinic cohort of patients with obstructive sleep apnea. Ann Am Thorac Soc. Published online November 4, 2020. doi:10.1513/AnnalsATS.202004-313OC