[Sleep in patients of a memory clinic : Clinical characteristics of the discrepancy between subjective and objective assessment].

Background: Dementia is often accompanied by sleep disturbances, whereby the diagnostics with subjective procedures and objective methods can produce discrepant results. The frequency and clinical characteristics of patients, whose subjective sleep efficiency was unimpaired and was in contrast to an objectively conspicuous sleep efficiency in the sense of an overestimation, were investigated in a memory consultation.

Methods: On 2 consecutive days, patients underwent guideline-oriented diagnostics for dementia (including mini-mental status examination, MMSE and clinical dementia rating, CDR), supplemented by a subjective (Pittsburgh sleep quality index, PSQI) and objective (overnight actigraphy) sleep assessment. Overestimation of sleep efficiency was defined as a subjective sleep efficiency (SSE) of ≥85% with an actigraphic sleep efficiency (ASE) of <85%.

Results: Of 45 patients (74.4 ± 7.8 years; 26 f/19 m; CDR < 1: n = 16, CDR = 1: n = 28; diagnostic groups according to ICD-10: F0: n = 39, F3: n = 5, Z03.x: n = 1) 10 showed an overestimation of sleep efficiency, who showed a lower MMSE score and a higher proportion of patients with a dementia syndrome (CDR = 1) when compared with the other three groups of SSE and ASE ≥85% (n = 17), SSE and ASE <85% (n = 9) and SSE <85% with ASE ≥85% (n = 9). Binary regression showed that MMSE remained an important predictor for overestimation of sleep efficiency.

Conclusion: Cognitive deficits in memory clinic patients appear to contribute to a poorer perception and/or an underreporting of objectively disturbed sleep. This could promote false negative subjective screening results in a diagnostic process in which a comprehensive sleep assessment is not routinely considered.