Sleep polygraphy: diagnostic value in depressive pseudo-dementia. Attempt to improve visual scoring by digital periodic analysis]

Pseudo depressive dementia is a common pathology for elderly patients. Classically, it is said that depression is taking the mask of dementia, but very often deterioration and depression are present at the same time. Sleep EEG can help the clinician to differentiate dementia and depression in pseudo depressive dementia. Slow Wave Sleep (SWS) is a good indicator of deterioration process. We tried to improve the sleep recording and analysis and our ability to differentiate SWS in this indication. We use a portable digital recording material (Hypnotrace). The signal is analysed by the association of a visual standard method to Digital Periodic Analysis (DPA) which is very sensitive to SWS. The visual analysis gives informations about the macroarchitecture of the night. The Digital Periodic Analysis gives at any moment the value of the wave frequency and thus informations about the microarchitecture. Our hypothesis is that this association helps to better recognise SWS and thus improves sleep EEG as a diagnostic tool in this indication.23 inpatients meeting both the criteria for major depression and dementia (DSM IV) have been recorded during two nights after 15 days of wash out and before antidepressant treatment. The recordings are analysed with the visual standard method and with the help of DPA. The patients are evaluated every 15 days during two months in order to define three groups based on the clinical evolution.The scoring with DPA is more sensitive to Slow Wave Sleep, particularly for the patients with good clinical evolution (with the strongest depressive component). Thus, this method could be a good diagnostic tool to differentiate dementia and depression in pseudo depressive dementia.