The Siesta Group

Welcome to The Siesta Group

The Siesta Group is a comprehensive service provider supporting the measurement of sleep, wakefulness and brain activity in clinical trials and research. This encompasses, among others, high quality services concerning polysomnography (PSG), pharmaco-electroencephalography (pharmaco-EEG) and event-related potentials (ERP). In a close cooperation with Philips-Respironics this also includes actigraphy. Our services range from consultation, site selection, site training, centralized data scoring and analysis, data quality control, to device rentals. 

Innovative software technology, secure data transfer, state-of-the-art scientific know-how, and flexible processes, all compliant with ICH-GCP and other regulation, ensure the best possible endpoints in measuring sleep, wake and brain activity in your trial.

The Siesta Group is the developer of Somnolyzer 24x7, the world’s most reliable and valid tool for computer-assisted sleep scoring. For clinical and diagnostic purposes, Somnolyzer 24x7 is now owned and marketed by Philips-Respironics. The use of Somnolyzer 24x7 and its related EEG analysis tools in your clinical trial ensures a quality of endpoints unsurpassed by other providers in the field.

Novel sleep endpoints reveal new details of drug action

In a recent retrospective analysis, to be presented at this year’s Congress of the European Sleep Research Society in Tallinn, Estonia, polysomnographic data from 36 insomnia patients receiving placebo and 400 mg almorexant (Actelion, Switzerland) in a random crossover fashion were subjected to a novel probabilistic sleep model. This model describes sleep in terms of probability curves, corresponding to classical sleep stages, with a 1 s resolution. Besides variables that correspond to classical sleep variables such as percentage in each sleep stage, novel types of variables were derived. These include a novel form of “sleep latency” in terms of percentiles of probability curves, and various types of “hidden states”, i.e., the extent of one probabilistic sleep stage hidden under another stage.

These novel variables revealed interesting additional information about the effects of almorexant. For instance, while the relative amount of the continuous “REM” stage increases under almorexant (19% vs. 16%, p=0.035), the percentiles of those amounts, i.e., the latencies to different amounts of “REM” – remain the same. Under probabilistic stage 2 the amount of “hidden” SWS increases by about 15% (p=0.013), pointing to interesting stabilizing effects on sleep.

The novel sleep model is available as part of Siesta Group services. We offer two pilot packages (20 or 35 recordings). Please inquire at This email address is being protected from spambots. You need JavaScript enabled to view it..


Service focus EEG: Does a compound cross the blood-brain barrier?

In most cases when a compound crosses the blood-brain barrier and thus elicits cerebral response, this can be clearly seen in the EEG, which thus becomes prime biomarker of this major compound characteristic, nicely complementing other biomarkers such as cerebral spinal fluid. In some cases, however, it is also important to prove that a compound does not cross the blood-brain barrier, e.g. to rule out potential adverse effects as a result. Potential indirect effects of a drug showing up in the EEG make the proof of non-crossing considerably more difficult, but several strategies can nevertheless lead to at least supporting evidence one way or another.
The Siesta Group helps sponsors explore any of the following paradigms that appear promising with respect to differentiating direct from indirect effects:

  • Indirect effects can be limited to certain areas of the brain – e.g. the limbic system – which can potentially be identified using EEG-based tomographic methods (e.g. LORETA)
  • Indirect effects are expected not to be dose-dependent, while direct CNS effects are
  • Indirect effects can be limited to certain spectral changes that help distinguish them from direct cerebral effects
  • Direct effects would be of the same kind that a positive control would elicit, signs of different changes would point to an indirect effect 

Please inquire at This email address is being protected from spambots. You need JavaScript enabled to view it. for more details.


Summer offer on retrospective analyses (EEG)

Electroencephalography (EEG) is often performed for safety reasons, mainly when epileptic seizures or other adverse events in the brain are expected. Research at The Siesta Group proves that such data can retrospectively also be used to reveal important EEG-based information about a drug’s efficacy. Although recorded in a different manner than classical quantitative EEG, state-of-the-art signal processing technology can still recover spectral information in the signal that provides evidence about where, when and to what extent a drug works in the brain.

We offer a pilot package (10 recordings of 10 min 19 lead EEG) for a standard retrospective analysis of your existing data, demonstrating our expertise and reporting standards. Please inquire at This email address is being protected from spambots. You need JavaScript enabled to view it..


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