**4.1 State of research**

134 Sleep Disorders

nearly accidents could be reduced with nCPAP therapy. A test for assessment of accident

Findley was found a correlation between the number of accidents and the error rate in a driving simulator test using *Steer Clear* and data's of *Accidents Authority* Virginia/USA. He also had verified a certain connection between accident rate and Sleep Apnea Syndrome and a dependence on the severity of the disease (Findley et al. 1989, 1995, 1999, 2000). Tests of this kind should be used only with great caution on the question of driving ability, because

Due to the simple construction *Steer Clear* and *Carda* offer also some advantages, because the technical effort is relatively low and even restricted patients can understand the task very well. However, the tests can only evaluate the response to nCPAP treatment in cases with

The severity of sleepiness, as assessed by the ESS, didn't correlate with the results of driving simulators. Sleepiness/drowsiness describes the degree of alertnes and will be influenced by central nervous system activation (Weeß et al. 2000). Because the test situation, the sleepiness is often compensated in moderate limitations (ESS < 13) – in our patients, the ESS score was on average = 11.0 – so that the error rate or track deviation showed no relevant dependence. However, in OSAS patients with profound sleepiness (ESS score > 13) a higher number of errors were found in *Carda* reached a higher (Randerath et al. 2000). Under the testing with *Carsim*, the number of patients who have had a pathological deviation is much higher. The complex task of interactive driving simulation recorded thus patients with reduced performance, special with difficulties in the divided attention and interactive activities. This could be proven, to persons whose driving performance was checked after alcohol administration with a driving simulator. In OSAS capacity was similar

Studies, which correlate the laboratory results of tracking tests with the real frequency of accidents, are still missing. It would be therefore desirable to obtain objective data on road authorities to characterize better any risk patients with this sensitive instrument. A trackingdriving simulator has a higher reality character than a reaction test, because it realized better the task, i.e. the reflection of driving situation (George 2000). Yet here, too, it is important to be sceptical about its evidence power, because the driving performance is dependent of many factors (e.g. responsible acting), which cannot be detected alone by simulation tests. A driving simulator test should be used only as one of several components in the complex

The interactive driving simulator test *Carsim*, designed by the Ambrock task force, can also be used for further questions: In OSAS patients may be improve due to different treatment modalities several sub-components of attention (such as selective attention, divided

Monotony **(+) +++**  Continuity **- ++**  Interactivity **- +++**  Usability **+++ ++** 

limited to persons with a blood alcohol of 95 25 mg/dl (George et al. 1996a).

Table 3. Design and properties of the two simulation programs

**Carda Carsim** 

risk would therefore be helpful.

it detected only a few aspects.

assessment of driving ability.

much higher error rate and can control it course.

Jenkins & Dallenbach (1924) could show for the first time that learning tasks which are presented before sleep could be keep better than tasks that are presented before wakefulness. This was confirmed in other studies (Hennevin et al. 1995, Smith 1996). The discovery of REM sleep (Dement & Kleitman 1957) was the start for a more specific research program in which certain stages of sleep each were assigned specific roles for the memory processes. As follow on one hand, REM sleep, was attributed partly memory-favouring effects because of its particular physiological changes, on the other hand, as well as the Slow Wave Sleep (SWS) was attributed the same effects (Hobson & McCarley 1977, Crick 1983, Wilson & McNaughton, 1994, Karni et al. 1994, Squire & Alvarez 1995).

One of the studies on cognitive deficits in the thinking, memory, communication and the ability to learn new information in OSAS patients comes from Kales (1985). In this study 76% of OSAS patients show cognitive deficits in all these areas. A study by Naëgelé et al. (1995) showed that the executive functions, which are important for the acquisition of information during memory processing in OSAS patients, were impaired.

It is assumed that in sleep disorders the often found reduced sleep quality leads, as a result of Slow Wave Sleep or REM suppression, increased nocturnal arousal responses or prolonged awakenings to a reduced recovery function of night sleep (Weeß et al. 1998a/b). According to Jennum et al. (1993), Insomnia and sleepiness affect cognitive functions. Patients with excessive daytime sleepiness complaints have special problems in situations of physical relaxation and during long monotonous concentration tasks (Schwarzenberger-Kesper et al. 1987).

Cassel et al. (1989) were able to detect in Sleep Apnea patients a reduced cognitive performance and a decreased non-verbal processing speed. In this connection they were able to detect a reduced cognitive processing speed on ZVT in OSAS patients. Also Kotterba et al. (1997) detect in 32 of 40 OSAS patients abnormal results on the ZVT. In another study of Kotterba et al. (1998), they found in OSAS patients an impairment of the central nervous system activation (*alertness*), of the selective attention and of the sustained attention. Barbé et al. (1998) verified in Sleep Apnea patients a decreased vigilance.
