Sleep apnea changes associated with cognitive impairment, brain structure alterations

Changes in obstructive sleep apnea status were linked with white matter integrity and cognitive performance, suggesting that timely intervention of OSA could help preserve brain health, researchers reported in JAMA Network Open.

“Impaired sleep function underlies cognitive dysfunction in OSA, from impairment of the precise temporal coordination of slow oscillations, sleep spindles and hippocampal ripples and glymphatic flow. These processes correlate with slow-wave activity and continuity, disrupted by OSA,” Min-Hee Lee, PhD, from the Institute of Human Genomic Study at the College of Medicine at Korea University Ansan Hospital, and colleagues wrote. “Direct neural injury also contributes to cognitive impairment in OSA, such as reduced gray matter volume or thickness and altered white matter integrity.”

The prospective cohort study included 1,110 adults (mean age, 58 years; 46.6% men) with both baseline (2011-2014) and 4-year follow-up (2015-2018) polysomnography, diffusion tensor imaging and cognitive assessment data. The neuropsychological assessment battery included verbal and visual memory, verbal fluency, Digit Symbol-coding, Trail Making Test-A and Stroop Test. Researchers assessed white matter integrity via fractional anisotropy and axial and radial diffusivity.

The primary outcomes were change over 4 years in neuropsychological performance and white matter integrity.

Participants were classified by OSA status: 458 were OSA-free, 72 had resolved OSA, 13 had incident OSA and 417 had persistent OSA.

Compared with the OSA-free group, incident OSA was associated with altered white matter integrity and concomitant changes in sustained attention as measured by the Digit Symbol-coding test score (difference = –3.2%; 95% CI, –5.2 to –1.2).

Individuals with resolved OSA demonstrated better visual recall during follow-up, measured by the Visual Reproduction-immediate recall test (difference = 17.5%; 95% CI, 8.9-26.1) and the Visual Reproduction-delayed recall test (difference = 33.1%; 95% CI, 11.3-54.9).

Among individuals aged older than 60 years, persistent OSA was associated with altered white matter integrity and cognition, measured by the Visual Reproduction-recognition test ( = –24.2; 95% CI, –40.7 to –7.7). In addition, sex was also associated with modifying OSA association with white matter integrity in men and with cognition in women.

“This cohort study found that OSA was associated with differences in cognitive performance and [white matter] integrity over time, especially in the older subgroup,” the researchers wrote. “These findings could provide potential targets for intervention to preserve brain health.”