Obstructive Sleep Apnea Might Contribute to Early Cognitive Decline, Study Finds

Distinct processes driven by obstructive sleep apnea might contribute to the occurrence of cognitive changes as early as middle age in otherwise healthy individuals in the United Kingdom, according to a study published in Frontiers in Sleep.

This study was conducted because OSA is a debilitating, chronic breathing disorder that occurs during sleep and results in a consistent pattern of cognitive deficits. According to the researchers, recent findings have indicated that these deficits, especially in middle-aged patients, might be provoked by cardiovascular and metabolic comorbidities, rather than specific OSA processes like oxidative stress and sleep fragmentation.¹

OSA’s established bidirectional connection to neurodegenerative disorders like Alzheimer disorder has emphasized the importance of disentangling some of the major cognitive neuromechanisms involved. The links between OSA and diseases like Alzheimer disorder are not well understood.

In this study, 27 middle-aged men with untreated OSA with no concomitant comorbidities were compared with 7 matched controls. Of the 27 patients, 16 had mild OSA, with a mean (SD) apnea-hypopnea index (AHI) of 11.7 (4.0) events/hour, mean (SD) age of 42.6 (8.2) years, and mean (SD) body mass index (BMI) of 26.7 (4.1) kg/m2, and 11 had severe OSA, with a mean (SD) AHI of 41.8 (20.7) events/hour; mean (SD) age of 46.9 (10.9) years, and mean (SD) BMI of 28.0 (3.2) kg/m2. The control patients had a mean (SD) AHI of 1.9 (1.4) events per hour, a mean (SD) age of 34.0 (9.3) years, and a mean (SD) BMI of 23.8 (2.3) kg/m2.

Following comparison, the researchers showed that the patients with OSA demonstrated poorer executive functioning and visuospatial memory and deficits in vigilance sustained attention and psychomotor and impulse control. They wrote that these findings largely align with previous studies of patients with OSA with associated multiple comorbidities, which similarly demonstrated aberrant executive functioning, visuospatial short-term memory, and deficits in vigilance and psychomotor control.

Upon review of results, the researchers saw for the first time decreased social cognition in the group of middle-aged patients with severe OSA. Past studies have shown that sleep deprivation has been shown to selectively impair accurate human facial emotion judgement, sleep fragmentation has been shown to result in deficits in recognizing emotional facial recognition, and there is evidence to suggest that emotional facial recognition can be dependent on sleep stage.

As a result of this knowledge, the researchers wrote, “it is likely that sleep fragmentation and associated sleep loss in our OSA patients, particularly REM-related fragmentation, may act to impair discrete affective neural systems, disrupting the identification of salient affective social cues.”

Other studies have also linked diminished quality and quantity of sleep to reduced altruism. The researchers noted that following this knowledge, their current research, and that approximately 1 billion people are estimated to have OSA, the clinical and societal impact of OSA’s effects on cognition needs urgent attention and a united multidisciplinary effort.

“It is increasingly evident that OSA’s functional neuropsychiatric impact may go well beyond OSA’s currently best recognized role in increasing driving and occupational accidents risks,” they said.

Furthermore, the authors highlight that their data reveal a threshold effect in the cognitive domain of executive functioning, and that it seems that cognitive deficits in this age groups are most apparent in male patients with severe OSA. These observations suggest the presence of widespread, intricate physiologic central nervous changes, and they support the importance of early treatment for this patient group, according to the researchers.

In a press release, Ivana Rosenzweig, PhD, lead study author and neuropsychiatrist, said, “This complex interplay is still poorly understood, but it’s likely that these lead to widespread neuroanatomical and structural changes in the brain and associated functional cognitive and emotional deficits.”²

Some limitations of this study include the small control group, multiple comparisons, and a cross-sectional design. The authors emphasized that an important limitation to any direct translational generalization of the findings lies in their inclusion of only male participants.

“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 researchers wrote.

References

1. Gnoni V, Mesquita M, O’Regan D, et al. Distinct cognitive changes in male patients with obstructive sleep apneoa without co-morbidities. Front Sleep. Published online April 6, 2023. doi: 10.3389/frsle.2023.1097946

2. Obstructive sleep apnea may directly cause early cognitive decline. News release. FRONTIERS; April 6, 2023. Accessed April 14, 2023. https://www.eurekalert.org/news-releases/985009