Action-Monitoring Dysfunction in Obstructive Sleep Apnea - A Pilot Study

The effects of an exercise intervention on executive function among overweight adults with obstructive sleep apnea

PURPOSE

Obstructive sleep apnea (OSA) is associated with poorer executive function. This study examined the effects of a comprehensive exercise intervention on executive function in overweight adults with mild and moderate-to-severe OSA.

METHODS

Participants aged between 30 and 65 years, with a body mass index (BMI) ranging from 27 to 42 kg/m^2, participated in a 6-week exercise program. Standardized polysomnographic recording methods provided total Apnea-Hypopnea Index (AHI) and level of hypoxemia. Executive function was assessed using the NIH Toolbox Flanker Inhibitory Control Test. A submaximal treadmill exercise test evaluated cardiorespiratory fitness. Participants with baseline total AHI between 5 and 14.9 events/h were classified as mild OSA and participants with baseline total AHI 15 ≥ events/h were classified as moderate-to-severe OSA.

RESULTS

Fifteen participants completed 18 exercise sessions. Significant differences between OSA categories at baseline were observed for sleep characteristics, but not for fitness or executive function. Wilcoxon Signed Rank Tests showed significant increases in median values for the Flanker Test in the moderate-to-severe category only, z = 2.429, p < .015, η² = .737.

CONCLUSION

Six weeks of exercise improved executive function in overweight individuals with moderate-to-severe OSA, but not in those with mild OSA.

Cognitive impairment in obstructive sleep apnea syndrome: a descriptive review

PURPOSE

Obstructive sleep apnea syndrome is a clinical sleep disorder defined by total or partial airflow restraint during sleep that results in fragmented sleep and hypoxemia, impacting negatively with cognitive functioning. This review was conducted on studies investigating structural brain alteration and cognitive impairment in obstructive sleep apnea syndrome.

METHOD

We searched on PubMed databases and screening references of included studies and review articles for additional citations. From initial 190 publications, only 17 met search criteria and described the cognitive impairment in obstructive sleep apnea syndrome.

RESULTS

Findings showed that patients with this syndrome had worse performance than healthy controls in attention, memory, and executive functions, showing specific neuroanathomical features. Cognitive impairment is also related to the severity of pathology. Treatment could improve certain cognitive aspects.

CONCLUSIONS

Cognitive deficits seem to be mainly attributable to decreased daytime vigilance and nocturnal hypoxemia.

Compensatory Neural Recruitment for Error-Related Cerebral Activity in Patients with Moderate-To-Severe Obstructive Sleep Apnea

(1) Background: Although it is known that obstructive sleep apnea (OSA) impairs action-monitoring function, there is only limited information regarding the associated cerebral substrate underlying this phenomenon. (2) Methods: The modified Flanker task, error-related event-related potentials (ERPs), namely, error-related negativity (ERN) and error positivity (Pe), and functional magnetic resonance imaging (fMRI) were used to evaluate neural activities and the functional connectivity underlying action-monitoring dysfunction in patients with different severities of OSA. (3) Results: A total of 14 control (Cont) subjects, 17 patients with moderate OSA (mOSA), and 10 patients with severe OSA (sOSA) were enrolled. A significant decline in posterror correction rate was observed in the modified Flanker task when patients with mOSA were compared with Cont subjects. Comparison between patients with mOSA and sOSA did not reveal any significant difference. In the analysis of ERPs, ERN and Pe exhibited declined amplitudes in patients with mOSA compared with Cont subjects, which were found to increase in patients with sOSA. Results of fMRI revealed a decreased correlation in multiple anterior cingulate cortex functional-connected areas in patients with mOSA compared with Cont subjects. However, these areas appeared to be reconnected in patients with sOSA. (4) Conclusions: The behavioral, neurophysiological, and functional image findings obtained in this study suggest that mOSA leads to action-monitoring dysfunction; however, compensatory neural recruitment might have contributed to the maintenance of the action-monitoring function in patients with sOSA.

Impaired conflict monitoring in cognitive decline

Resolving conflicts is an important cognitive ability of executive function, and it may decrease with cognitive decline. The flanker task is a practical test used to assess the ability to suppress responses that are inappropriate in a particular context. The aims of the present study were to investigate conflict monitoring of cognitive control in subjects with different levels of cognitive impairment, and clarify the usefulness of the flanker task in screening cognitive decline. We recruited 50 subjects with mild cognitive impairment (MCI) and 34 patients with Alzheimer's disease (AD), and 44 mentally healthy elderly subjects as a control group. To evaluate cognitive performance, each participant underwent a neuropsychological assessment using the Cognitive Abilities Screening Instrument and a modified flanker task. Compared with the normal controls and those with MCI, the patients with AD had a significantly lower accuracy rate and longer reaction time in both congruent and incongruent trials. The diagnosis of AD predicted significantly poorer performances on the flanker tasks. Furthermore, behavioral data of the patients with AD were significantly correlated with the results of neuropsychological tests. Our results indicated that executive cognitive deficits in conflict monitoring as detected by the flanker task were significantly impaired in the patients with AD. The flanker task could be a quick and easier alternative tool for screening AD among elderly people with suspicious cognitive impairment.

The impact of obesity in cognitive and memory dysfunction in obstructive sleep apnea syndrome

OBJECTIVE

Obstructive sleep apnea (OSA), a sleep disorder, results in decreased daytime alertness and neurocognitive dysfunction. Obesity is considered a major risk factor for the development and progression of OSA and the resulting cognitive dysfunction. However, the effect of obesity on neurocognitive dysfunction in OSA has been rarely investigated.

METHODS

Eighty-three patients with moderate to severe OSA syndrome were recruited in our study. After matching for education, age, and body mass index (BMI), 40 patients were enrolled into our study with matched obese (BMI ≧ 30) and non-obese (BMI < 30) groups. All enrolled patients completed a polysomnographic study, sleepiness questionnaires, and attention, cognitive, and memory function tests.

RESULTS

Compared to obese OSA patients, non-obese OSA patients had shorter reaction times in the psychomotor vigilance task but not the Flanker or Stroop cognitive tasks. Additionally, obese OSA patients had a reduced capacity for working memory relative to non-obese OSA patients.

CONCLUSIONS

Obesity had a significant effect on OSA patients in our study, including delayed reaction times in the psychomotor vigilance task and a decrease in working memory.