Clinical significance of sleep-disordered breathing in Alzheimer's disease. Preliminary data.

In a study of 15 probable Alzheimer's patients and 12 healthy elderly control subjects, Alzheimer's patients had a significantly higher apnea index (patients versus controls, mean +/- SD: 6.3 +/- 6.6 vs 1.8 +/- 2.7, P less than .05) and greater maximal duration of apnea (patients versus controls, median: 50.0 vs 28.5 seconds, P less than .001), but no significant increase in oxyhemoglobin desaturation compared with controls. (The accepted normal threshold for abnormality is an apnea index more than 5.) Although three of seven psychometric tests (odd-even, category retrieval, face-hand test) showed diurnal effects on one or more of their subscores, with Alzheimer's patients having significantly poorer scores at the AM than at PM testing, overnight change scores in the psychometric tests were not significantly correlated with severity of sleep-disordered breathing. Further, only 18.1% of the disruptive (ie, requiring intervention) nocturnal behaviors of the Alzheimer's patients were temporally linked to sleep-disordered breathing. The current data suggest that sleep-disordered breathing in nonmedicated Alzheimer's patients is relatively mild and is not a predictor of either overnight mental status changes, of disruptive nocturnal behaviors, or of daytime behavioral fluctuations. Additional studies of more severely demented patients and possibly of sleeping pill effects would be useful in further evaluating the role of sleep apnea in Alzheimer behavioral changes.