Obstructive Sleep Apnea Status Tied to White Matter Integrity, Cognition

Dynamic changes in the status of obstructive sleep apnea (OSA) have been shown to be significantly associated with white matter integrity and cognition, which varies according to sex and age. These are the findings of a prospective cohort study published in JAMA Network Open.

Researchers sought to evaluate the association of OSA with white matter integrity and cognition over a 4-year period in a community-based, middle-aged and older adult population of South Korean participants. The participants had both baseline (2011 to 2014) and 4-year follow-up (2015 to 2018) polysomnography (PSG), diffusion tensor imaging (DTI), and neuropsychological assessment data available for interpretation. Individuals with neurologic disorders, anomalous findings on brain magnetic resonance imaging (MRI), or inadequate quality of the assessments were excluded from the study. All of the data were analyzed between March 2021 and November 2021.

All study participants underwent PSG at home with the use of portable devices. The presence and severity of OSA were based on the apnea-hypopnea index, in which individuals classified as OSA-free experienced 5.0 or fewer events per hour, those with mild OSA experienced 5.0 to 14.9 events per hour, participants with moderate OSA experienced 15.0 to 29.9 events per hour, and individuals with severe OSA experienced 30.0 events per hour.

Changes in OSA status over 4 years were established by comparing the results of PSG at baseline and at follow-up, and dividing the individuals into the following 4 groups:

• OSA-free;
• Resolved OSA;
• Incident OSA; and
• Persistent OSA.

To explore the interactions with age and sex, all participants were subgrouped as aged older than 60 years vs aged 60 years or younger, as well as men vs women.

The neuropsychological assessment battery comprised:

• Story Recall (SR),
• Visual Reproduction (VR),
• Phonemic verbal fluency (VF1) and categorical verbal fluency (VF2),
• Digit Symbol-coding (DS),
• Trail Making Test-A (TMA), and
• Stroop Test-Word Reading (STROOP1) and Stroop Test-Color Reading (STROOP2) tests.

Immediate recall (IR), delayed recall (DR), and recognition (RECOG) were included in the SR and VR tests. For all of the tests other than TMA, higher scores were indicative of better performance.

Overall, 1998 individuals were evaluated for study eligibility, with 888 excluded according to enrollment criteria. Thus, a total of 1110 participants were included in the study (mean age, 58 years; 46.6% men). Of the 1110 participants, 458 were classified as OSA-free, 72 with resolved OSA, 163 with incident OSA, and 417 with persistent OSA.

Study findings revealed that incident OSA was associated with altered white matter integrity and with concomitant changes in sustained attention compared with OSA-free participants (eg, change in DS score: –3.2%; 95% CI, –5.2% to –1.2%). Individuals with resolved OSA demonstrated better visual recall at follow-up (change in VR-IR test: 17.5%; 95% CI, 8.9%-26.1% and change in VR-DR test: 33.1%; 95% CI, 11.3%-54.9%).

Among participants in the older age-group only, persistent OSA was associated with altered white matter integrity and cognition (eg, VR-RECOG test: β= –24.2; 95% CI, –40.7 to –7.7). Sex also was associated with modifying the association of OSA with white matter integrity of the left genu of corpus callosum, the left posterior internal capsule, and the right middle cerebellar peduncle in men only, as well as with cognition in women only (eg, VR-ER test: β=33.4; 95% CI, 19.1-47.7).

The present study has several limitations. The study results are not readily generalizable to the symptomatic clinical or severe OSA populations, since the participants were not a clinical population, they mainly had mild OSA, and they were not particularly sleepy at the time of the testing. Additionally, the sample sizes of the resolved OSA and incident OSA groups were relatively small.

The researchers concluded that “It is possible that adequate interventions for OSA could better preserve brain health in middle to late adulthood.”

Disclosure: Some of the study authors have declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of authors’ disclosures.