Study of cognitive impairment in subjects with obstructive sleep apnoea using Addenbrooke’s Cognitive examination(ACE-R)

Introduction: Obstructive sleep apnoea (OSA) is known to cause cognitive impairment. ACE-R is an accepted short cognitive test to screen for cognitive impairment but not studied in subjects with OSA. Hence this study was undertaken to evaluate the pattern of cognitive impairment in subjects with OSA and compare with normal individuals. Material and Methods: 36 patients diagnosed with OSA aged between18-59 years, who had not been initiated on treatment with a minimum education of high school level and 36 matched controls without OSA were studied. Subjects and controls with known cognitive impairment, psychiatric illness, alcohol abuse or other significant systemic illness were excluded. The subjects and controls were evaluated for cognitive function by using ACE-R along with time to response test using Harvard designed car simulator driving test. Results: The mean ACE-R score in subjects with OSA was 75 in cases whereas in controls it was 87. The reaction time was 0.4 seconds in the cases whereas in controls it was 0.34. The difference was statistically significant in both. ACE-R negatively correlated with Apnoea hypopnea index(AHI), Oxygen Desaturation Index(ODI), Lowest Oxygen saturation, and Epworth sleepiness score(ESS). Of the domains of ACE-R memory had a strong (-0.3) correlation with the lowest saturation recorded. Conclusion: ACE-R is a valid tool that can be used in subjects with OSA to screen for cognitive dysfunction since it's significantly lower in subjects with OSA as compared with subjects without OSA. Simulated reaction time is higher in subjects with OSA. Low oxygen saturation during the obstructive events causes an effect on memory.