Correlation between measures of sleep-disorded breathing and cognitive impairment.

Rationale:To analyse relationships between measures of sleep-disordered breathing and neuropsychological functioning in OSA patients with different parameters of hypoxic burden. Patients and methods:In 136 newly diagnosed OSA patients(mean age 60yrs,mean BMI 33)we studied apnoea hypopnoea index(AHI),oxygen desaturation index(ODI),mean and minimum nocturnal saturation(SpO2mean),mean of the minimum nocturnal saturations,time with an O2 saturation below 90%(TD90),mean decrease from mean saturation,mini-mental state examination (MMSE),the Rey auditory verbal learning test (RAVLT),the Corsi block-tapping and the digit span task exercises,the speed and capacity of language processing test(SCOLP),Multiple Features Targets Cancellation(MFTC),Raven’s matrices,Stroop test. Results:34% of patients had neuropsycological deficits.At the univariate linear regression,but not at the multivariate regression,partial pressure of oxygen in the blood during awakening and minimum nocturnal saturation during sleep represented the most number of the abnormal cognitive functions.RAVLT,SCOLP and Raven’s matrices were affected the most.At the multivariate regression SpO2mean correlated with the digit span task exercises,SCOLP test and the Stroop test,whereas AHI correlated only with RAVLT and ODI only with Stroop test.BMI correlated with RAVLT and SCOLP;TD90 with RAVLT.The mean decrease from mean saturation correlated with Corsi and MTFC tests both in severe and in mild-moderate OSA patients. Conclusion:not only the total time in hypoxia and its severity but also the amplitude of hypoxiemic swings are associated with the cognitive impairment of OSA patients, and this effect is significant also in mild to moderate cases.