Changes in the sleep and waking EEGs of nondemented and demented elderly subjects

Sleep and waking EEGs from 11 healthy nondemented elderly men and from ten inpatients for whom the diagnosis was probable senile dementia of Alzheimer's type (SDAT), were monitored in the subjects' typical home or ward environments or in the sleep laboratory, according to their customary sleep schedules. Aged normal subjects (age range, 56-85 years) had less Stage 3 and Stage 4 sleep, less REM sleep, and more wakefulness than normally observed in young adults. Patients with SDAT (age range, 56-88 years) had even less Stage 3 sleep, no Stage 4 sleep, and very little REM sleep, and experienced fragmentation of their sleep, with frequent awakenings. These sleep variables were significantly different in the SDAT and control groups (MANOVA). Examination of the 24-hour plots of sleep/waking patterns revealed prominent fragmentation of the diurnal sleep/waking rhythm in SDAT patients, with frequent daytime napping and nighttime periods of wakefulness. In addition, significant group differences were observed for the EEG variable, dominant occipital frequency. More qualitative EEG variables (diffuse slowing, spindle activity, and paroxysmal discharges) also differed between groups. It is suggested that correlative neuropathologic data might provide an understanding of the basis for the sleep, EEG, and mental-function factors that undergo change in SDAT.