Sleep-disordered breathing in normal and pathologic aging.

In a study of sleep-disordered breathing among 139 elderly individuals, sleep apnea (defined as 5 or more apneas per hour) occurred in 34 (41.7%) Alzheimer's subjects compared with 56 (5.4%) healthy controls, 35 (11.4%) depressive subjects, and 24 (16.7%) patients with mixed symptoms of both cognitive impairment and depression (p less than .001). Alzheimer's patients had a significantly higher proportion of NREM-related than REM-related apnea. Moreover, a significant (p less than .01) positive correlation between the apnea index and severity of dementia, as measured by the Blessed Dementia Rating Scale, was found in apnea-positive Alzheimer's patients, as well as in the entire sample of Alzheimer's patients (p less than .05). No such correlation was found in the mixed-symptoms group. Possible clinical and neuropathologic implications are discussed.