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• Using electroencephalographic sleep data from a sample of 235 elderly subjects, discriminant function analyses of sleep alterations in depression and dementia were performed. Overall, 80% of patients were correctly classified using a backward discriminant function analysis, and 81% with a general stepwise discriminant function analysis. Four measures contributed to the separation of depressed and demented patients: rapid eye movement (REM) sleep latency (lower in depressives); REM sleep percent (higher in depressives); indeterminate non-REM sleep percent (higher in demented patients, reflecting greater loss of spindles and K complexes); and early morning awakening (more marked in depressives). When both discriminant functions were subjected to cross-validation in independent subsamples, both procedures correctly identified 78% of patients. The classification functions derived from nondemented depressed and nondepressed demented patients were applied to a mixed-symptom group (n = 42). Overall, 27 patients (64%) with either depressive pseudodementia or dementia with depressive features were correctly classified using the same four predictor variables. These findings suggest that sleep physiological alterations of depression and dementia reflect between-group differences in sleep continuity, sleep architecture, and REM sleep temporal distribution, and that the differences are statistically reliable, in both diagnostically pure and mixed clinical presentations. These findings are discussed in the context of current hypotheses of sleep regulation and its mechanisms.

• Decreased slow-wave sleep (SWS) and sleep continuity are major effects of healthy aging and of associated psychopathological states. Using sleep deprivation, we studied the extent to which age- and psychopathology-related sleep "decay" is reversible in aged normal, depressed, and demented subjects. Depression or probable Alzheimer's dementia compromised the augmentation of sleep continuity and SWS seen in healthy elderly following sleep deprivation. Rapid eye movement (REM) latency decreased during recovery sleep in the controls but increased in both patient groups. Compared with demented patients, depressed elderly had greater severity of sleep continuity disturbance both before and after sleep deprivation, a more protracted course of recovery sleep, and increased slow-wave density in the second non-REM (NREM) sleep period (during recovery). The REM sleep time was diminished in dementia compared with depression both at baseline and during recovery sleep. These differential effects of age, health, and neuropsychiatric disease on recovery from sleep loss are relevant to recovery or reversal theories of sleep and have implications for daytime well-being in the elderly.

In a retrospective study of 80 patients over 55 years old, the efficacy of lumbar puncture in evaluating elderly demented patients was examined. Despite a cost of $381 per procedure, in addition to cerebrospinal fluid (CSF) evaluation, no diagnosis was made on the basis of the information obtained in any of the patients (53 per cent) who underwent lumbar puncture. The only abnormalities found were 11 cases of nonspecific elevations in CSF protein and one case of abnormal cellularity not related to bacterial infection. An additional 422 cases of dementia from other series were reviewed, and only four patients were found whose diagnosis could have been made by lumbar puncture—one patient had neurosyphilis, and the other three were postencephalitic. In addition, the literature on complications of lumbar puncture was reviewed. There were no serious complications of lumbar puncture in the present study. The authors concluded that although it is low‐risk, lumbar puncture cannot currently be recommended for routine use in the evaluation of elderly demented patients, but should be used in evaluating demented patients under 55 years of age, patients with rapid onset or progression of dementia, patients with syphilis serology in suspected cases of viral encephalitis, and patients with signs and symptoms of fungal meningitis. J Am Geriatr Soc 33:397, 1985