Treatment of rest‐activity disorders in dementia and special focus on sundowning

Cognitive performance and sleep quality seem to be closely related. With increasing age qualitative as well as quantitative changes in sleep occur, and approximately 38% of over-65-year-olds report sleep disturbances according to epidemiological studies (Foley et al., 1995). Subjectively experienced sleep disturbances correlated negatively with cognitive performance in a 3-year follow-up (Jelicic et al., 2002 ). In demented patients, the extent to which night sleep is disturbed is said to correlate with severity of dementia (Bliwise et al., 1995). Apart from somatic diseases a lack of daily routine, insufficient light intensity, napping and reduced physical activity surely facilitate sleep disturbances (Shochat et al., 2000). While napping may be an expression of a disrupted sleep-night-structure, it has been shown to induce changes in the circadian rhythm when performed in the evening hours (Yoon et al., 2003). To add to complexity, other factors have to be considered in old age like restless leg syndrome, a sleep apnea syndrome or nycturia or an enuresis nocturna and are related to dementing conditions (Bassetti et al., 1996; Bliwise et al., 2004). The interface between sleep structure and cognition deserves more attention since it might deliver explanations for phenomena like sundowning and thus opens access to an adequate and successful therapy. The disturbance of sleep sequence could be a correlate of an insufficient dynamic use-independent stabilization of old memory contents in longer persisting sleep disturbances (Staedt and Stoppe, 2004). In addition, external factors gain more relevance because of the fragility of the networks. According to the literature, 34–43% of the patients with AD experience sleep disturbances (Cacabelos et al., 1996; Tractenberg et al., 2003). The most spectacular disturbance is sundowning. This term describes a delusional and often delirious state which occurs at twilight or during early night (Bliwise, 1994). Data on the prevalence are varying from 10–25% in institutionalized patients (Evans, 1987; Martin et al., 2000) and numbers are even higher in Alzheimer’s patients living at home, reaching up to 66% (Gallagher-Thompson et al., 1992). Patients with dementia develop a disturbance of the rest-activity cycles, which—usually in severe stages—can result in a total disruption of the rhythm (van Someren et al., 1996; Werth et al., 2002). Its treatment proves difficult in many cases: confusion, impaired cognition, excessive sedation with danger of falling are side effects of the application of neuroleptics and benzodiazepines (Ancoli-Israel and Kripke, 1989; Stoppe et al., 1999). It also represents a substantial burden for the spouses, who—when sharing the nights—show similar disturbances of the rest-activity pattern in actigraphically controlled studies (Pollak and Stokes, 1997). According to a large study in Germany 51% of caregivers experience disruptions of sleep continuity, on average 2.4 per night (Graessl, 2000). Rest-activity disturbances represent one of the main factors for nursing home admission of patients with dementia (Coen et al., 1997; Pollak et al., 1990). Since an Alzheimer pathology underlies approximately 70% of dementing diseases (Neuropathology Group of the MRC CFAS, 2001), the potential impact of the neurophysiological changes of Alzheimer’s dementia on the rest-activity regulation should be discussed. Neuronal degeneration in the Nucleus basalis Meynert (NBM) is one of the most prominent features (McGeer et al., 1984; Reinikainen et al., 1988). A reduction of cholinergic inputs to the suprachiasmatic nucleus (SCN) impairs the synthesis and expression of neuropeptides (Madeira et al., 2004) The reduced activity of the SCN, which is involved in the regulation of temperature, of arousal level or sleep-wake rhythm via projections to the anterior and posterior hypothalamus (Miller, 1993), leads to fragility of