Recent debates have surrounded whether cognitive deficits, specifically in middle-aged patients, may be driven by cardiovascular and metabolic comorbidities instead of distinct obstructive sleep apnea processes.
Obstructive sleep apnea (OSA) may lead to cognitive changes occurring as early as middle ages in otherwise healthy individuals, according to a study published by Frontiers in Sleep. The study noted that OSA is a multisystem, debilitating, and chronic breathing disorder that may cause a relatively consistent pattern of cognitive deficits.
The investigators added that recent arguments have surrounded whether cognitive deficits, specifically in middle-aged patients, may be driven by cardiovascular and metabolic comorbidities instead of distinct OSA-processes.
“Cognitive functions traditionally comprise broad domains of attention and memory, as well as those of higher order cognitive skills such as planning, problem-solving, and mental flexibility (grouped together as executive function), visuospatial abilities, processing speed, and both expressive and receptive language,” the study authors wrote. “Historically, a body of work has suggested significant impact of OSA on: attention and vigilance, long-term verbal and visual memory, expressive and receptive language, and visuo-spatial and constructional abilities.”
According to the study, the link between cognition, OSA, and aging is challenging to fully discern, noting that aging has been shown to be independently linked with physiological changes that may predispose individuals to OSA. This link may be attributed, in part, to changes in upper airway morphology that may cause a decrease in upper airway dilator muscle function at sleep onset, which contributes to age-related propensity for upper airway collapse as a result of negative pressure independent of body mass index, the investigators said.
For the study, the authors sought to define cognitive performance in a group of 27 middle-aged male patients with untreated OSA and no concomitant comorbidities to compare with 7 matched controls (AHI mean ± S.D.: 1.9 ± 1.4 events/h; mean age 34.0 ± 9.3 years; mean BMI 23.8 ± 2.3 kg/m2). Among the 27 patients enrolled, 16 had mild OSA (AHI mean ± S.D.:11.7 ± 4.0 events/h; mean age 42.6 ± 8.2 years; mean BMI 26.7 ± 4.1 kg/m2), and 11 had severe OSA (AHI 41.8 ± 20.7 events/h; age: 46.9 ± 10.9 years, BMI: 28.0 ± 3.2 kg/m2).
Participants received domiciliary respiratory testing via WatchPAT system as well as a video-polysomnography (vPSG) in the sleep center. Full night vPSG recordings were based on the international 10:20 system and for purposes of the PSG scoring, 6 EEG channels were referenced to the mastoid. This was used with electrooculography, submental-electromyography, respiratory inductance plethysmography, nasal pressure sensor, oronasal thermistor, pulse-oximeter, 2-lead electrocardiogram, body position detector, and synchronized audio-visual recording.
The results show that in the patient cohort, there was poorer executive-functioning, visuospatial memory, and deficits in vigilance sustained attention, psychomotor, and impulse control. The investigators also observed, for the first time, effects on social cognition in the study group of male, middle-aged OSA patients.
“Distinct deficits were observed in the tests investigating cognitive domains of vigilance, executive functioning, short-term visual recognition memory and social and emotion recognition, with the greatest number of differences between controls and those with severe OSA,” the study authors wrote. “Whilst subjects with mild OSA performed better than those with severe OSA on most of those same tasks, they were rarely worse than controls.”
The investigators concluded it is likely that sleep fragmentation and associated sleep loss in OSA patients, and particularly REM-related fragmentation, may impair discrete affective neural systems and disrupt the identification of salient affective social cues.
“In conclusion, future multi-center multi-modal longitudinal studies should confirm these findings, as well as decipher how these cognitive deficits may interplay in men and women with other comorbidity-driven impairments over time,” the authors wrote.
Gnoni V. et al. Distinct cognitive changes in male patients with obstructive sleep apnoea without co-morbidities. Frontiers in Sleep. DOI=10.3389/frsle.2023.1097946 https://www.frontiersin.org/articles/10.3389/frsle.2023.1097946. ISSN=2813-2890. Accessed June 6, 2023.