Maturitas 77 (2014) 305–310

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Maturitas journal homepage: www.elsevier.com/locate/maturitas

Review

Considering the senses in the diagnosis and management of dementia Sophie Behrman, Leonidas Chouliaras, Klaus P. Ebmeier ∗ Department of Psychiatry, University of Oxford, Warneford Hospital, Oxford OX3 7JX, UK

a r t i c l e

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Article history: Received 3 January 2014 Accepted 7 January 2014 Keywords: Vision Hearing Smell Touch Behaviour Ageing

a b s t r a c t Associations between dementia and impairments in hearing, vision, olfaction and (to a lesser degree) taste have been identified. Hearing impairment has been shown to precede cognitive decline, but it is not clear if the hearing loss is an early marker of dementia or a modifiable risk factor. Olfactory impairment is seen in many neurodegenerative conditions, but it has been shown that those with dementia have particular difficulties with the recognition and identification of odours rather than the detection, suggesting a link to impairment of higher cognitive function. Olfactory impairment has been shown to be predictive of conversion from mild cognitive impairment to Alzheimer’s disease with 85.2% sensitivity. As cognitive function deteriorates, the world is experienced at a sensory level, with reduced ability to integrate the sensory experiences to understand the context. Thus, people with dementia are very sensitive to sensory experiences and their environment needs to be managed carefully to make it understandable, comfortable, and (if possible) therapeutic. Light can be used to stabilise the circadian rhythm, which may be disturbed in dementia. Music therapy, aromatherapy, massage and multisensory stimulation are recommended by NICE for the management of behavioural and psychological symptoms of dementia (BPSD), although the mechanisms behind such interventions are poorly understood and evidence is limited. Sensory considerations are likely to play a greater role in dementia care in the future, with the development of purpose-built dementia care facilities and the focus on non-pharmacological management strategies for BPSD. © 2014 Elsevier Ireland Ltd. All rights reserved.

Contents 1. 2.

3.

4.

5. 6. 7.

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hearing impairment and dementia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.1. Hearing loss and cognitive testing performance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2.2. Underlying mechanisms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Other sensory impairments and dementia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.1. Olfactory impairment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.2. Taste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3.3. Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sensory considerations in the management of dementia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. Vision . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.2. Hearing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.3. Smell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.4. Touch . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.5. Taste . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multisensory stimulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Technology and building for the sensory experience of dementia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

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Abbreviations: NICE, National Institute for Health and Care Excellence; BPSD, behavioral and psychological symptoms of dementia; MMSE, mini mental state examination; AD, Alzheimer’s disease; PD, Parkinson’s disease; UPSIT, University of Pennsylvania smell identification test; MCI, mild cognitive impairment; OR, odds ratio; DLB, dementia with Lewy bodies; AMD, age-related macular degeneration; CBS, Charles-Bonnet syndrome; ADL(s), activities of daily living; CGI, Clinical Global Impression of Change. ∗ Corresponding author. Tel.: +44 1865 226469; fax: +44 1865 793101. E-mail address: [email protected] (K.P. Ebmeier). 0378-5122/$ – see front matter © 2014 Elsevier Ireland Ltd. All rights reserved. http://dx.doi.org/10.1016/j.maturitas.2014.01.003

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Contributors and their role . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Competing interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Funding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Provenance and peer review . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

1. Introduction

3. Other sensory impairments and dementia

Hearing loss and other sensory deficits, such as olfactory and visual disturbances have been linked with cognitive decline and the onset of dementia. It is unclear whether hearing loss and other sensory deficits are risk factors for the development of dementia, early stages or part of a continuum of age-related degeneration [1]. Studies have suggested that hearing loss can be an early sign of dementia onset and suggested that hearing studies should be incorporated in routine dementia screening. In the first part of this review we summarise the evidence providing links between hearing loss and other sensory impairments with cognitive dysfunction and onset of dementia. In the second part we examine the management of behavioural and psychological symptoms of dementia using a sensory framework.

3.1. Olfactory impairment

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It has been suggested that hearing loss may impair the performance on cognitive tests without an underlying cognitive decline. However, a study by Uhlmann et al. showed that hearing-impaired patients with dementia scored lower on both written and standard MMSE tests, when compared with hearing-unimpaired patients, suggesting that cognitive dysfunction in hearing-impaired patients is not just an artefact of the testing procedure [11].

A meta-analysis by Mesholam et al. has found an association between olfactory impairment and Alzheimer’s disease (AD), as well as Parkinson’s disease (PD) [14]. In this study, there were no differences between the diseases, suggesting that olfactory impairment may just be a marker for any of the neurodegenerative conditions. On the other hand, in a meta-analysis of 81 published studies, Rahayel et al. found that olfactory impairments are present both in AD and PD patients, but AD patients perform worse in odour identification and odour recognition tasks, while PD patients perform worse in odour detection tests. Such data suggests that AD patients are impaired in higher-level olfactory cognition tests, while PD patients are more impaired in lower-level perceptual tests [15]. Moreover, olfactory impairment, especially severe anosmia, has been linked with the risk of developing dementia in PD [16]. Yet, in a prospective cohort study, Swan et al. showed that olfactory impairment may also predict specific decline of verbal memory in non-demented elderly [17]. Olfactory impairment in the elderly was further found to correlate with neurocognitive tests of immediate and delayed recall, category fluency and naming objects as well as with MRI hippocampal volumes [18]. Olfactory impairment, using the University of Pennsylvania smell identification test (UPSIT), along with measures of verbal memory, functional activities scale, MRI hippocampal volumes and MRI entorhinal cortex volumes have been part of the combination of early markers in a study predicting the conversion of mild-cognitive impairment (MCI) to AD with 85.2% sensitivity [19]. Djordjevic et al. showed in a cohort study that patients with MCI have deficits in all domains of olfactory function, i.e. detection threshold, discrimination and identification, and those functions deteriorate further with the progression to AD [20]. In a five year prospective cohort study, Schubert et al. noted that olfactory impairment at baseline can predict onset of cognitive decline, measured by MMSE, with an odds-ratio (OR) of 6.6 [21]. Similarly, Conti et al. found that, in a two year longitudinal cohort study, olfactory deficits in MCI subjects may be associated with an increased risk of conversion to AD, with an OR of 5.1 [22], while Sohrabi et al. showed that in a three year prospective follow up study olfactory impairment can predict cognitive decline in elderly individuals [23]. Seligman et al. showed that olfactory impairment in demented patients correlated with the levels of apathy [24]. Finally, anosmia in dementia has been strongly associated with dementia with Lewy bodies (DLB), and it has been suggested that olfactory function tests may be used for the identification of patients with DLB [25–27].

2.2. Underlying mechanisms

3.2. Taste

A common mechanism of hearing impairment and the development of age-related cognitive decline and dementia has been proposed, involving mitochondrial dysfunction and increased oxidative stress. Treatment strategies like caloric restriction and their underlining biological mechanisms, such as up-regulation of sirtuins, have been involved in delaying the onset of age-related cognitive decline, as well as age-related hearing loss [12,13].

Apart from the olfactory impairment, limited evidence indicates a link between taste impairment and dementia. A cohort study by Lang et al. found a correlation between the severity of dementia and taste impairment which was especially prominent in PD patients, even after controlling for confounding effects of age, smoking and alcohol consumption [28]. In a cohort study by Steinbach et al. taste impairment was associated with MCI and AD patients when

2. Hearing impairment and dementia Early studies have found a correlation between hearing loss and dementia in elderly populations [2,3]. Uhlmann et al. found an association between hearing impairment and dementia in a case–control study, the severity of hearing impairment was linked with the relative odds of incidence of dementia [4]. Moreover, findings from a prospective cohort study have suggested that central auditory dysfunction may precede the onset of dementia for many years and could be used as an early risk marker for dementia [5,6]. Lin et al. have confirmed the association between hearing loss and dementia in prospective cohort study [7]. They have concluded that future research needs to clarify whether hearing loss is an early stage of dementia or a modifiable factor that can affect the risk of developing dementia [7]. In a cross-sectional cohort, Lin et al. found that a hearing loss of 25 dB correlated with cognitive loss equivalent to an extra 6.8 years of age [8]. Cohort studies in Japanese and Italian elderly populations have highlighted a correlation between auditory function and performance on MMSE score, suggesting that hearing impairment is associated with cognitive dysfunction [9,10]. 2.1. Hearing loss and cognitive testing performance

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compared with control subjects, while there was no difference of taste impairment when comparing MCI subjects with AD patients [29]. 3.3. Vision Various types of visual impairment have been observed in dementia sufferers; however it is not yet clear whether visual impairment precedes dementia onset and whether it could be used as an early marker for dementia risk. A wealth of evidence has suggested that elderly with visual impairment perform worse on the conventional cognitive tests, and alternative versions for visually impaired patients should be used [30]. Uhlmann et al. have found that visual impairment is associated with increased risk for developing AD and increased severity of AD, however they could not identify a dose–response relationship [31]. Regarding specific types of visual impairment in dementia, contrast sensitivity has been found to be altered in AD patients when compared with agematched controls [32]. In concordance with this Rizzo et al. found that contrast sensitivity is impaired in AD patients, they found that visual attention, colour, shape-from-motion, visuospatial construction and visual memory were also affected in AD patients [33]. In an eight years prospective cohort study of 625 elderly individuals, Rogers et al. found that poor vision was associated with increased risk of developing dementia, while subjects with unimpaired vision at baseline had a 63% reduced risk of developing dementia. In addition, untreated poor vision was associated with a higher risk of developing dementia, when compared with participants, who had at least one previous eye procedure [34]. It has been proposed that age-related macular degeneration (AMD) may be associated with dementia. In a large cohort of 65,894 AMD patients recruited from the NHS, no association was found between AMD and dementia, apart from the fact that dementia sufferers were less likely to receive treatment for AMD [35]. Another common age-related ophthalmologic disturbance, the CharlesBonnet syndrome (CBS) has been linked with the onset of dementia. Patients with CBS experience neuropsychological deficits associated with early dementia stages [36]. As both CBS and DLB involve complex visual hallucinations, it has been suggested that CBS is particularly associated with the development of DLB [37,38]. CBS has an estimated prevalence of 10–15% in people with visual impairment and is underdiagnosed [37]; often the hallucinations are not recognised as such by the sufferer or clinician, or are so benign that medical intervention is not sought or is actively avoided due to perceived stigma of a potential diagnosis of mental illness. Given the high comorbidity of visual impairment with dementia in older age groups, likely compounded by poor concordance with use of glasses, it is likely that CBS is particularly prevalent in dementia. It is possible that insight, which is usually retained in CBS, is lost in those with dementia due to poor cognitive function leading to hallucinations being perceived as threatening and possibly incorporated into delusional beliefs. 4. Sensory considerations in the management of dementia Management of certain aspects of dementia, in particular behavioural and psychological symptoms may also be considered using a sensory framework. The NICE Guidelines [39] currently recommend a trial of the following interventions for patients with agitation in dementia: • • • •

Aromatherapy Therapeutic use of music and/or dancing Animal assisted therapy Massage

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• Multisensory stimulation Such interventions may well be operating through their effects on the senses, whether smell, sight, hearing or touch, or a combination of many in multisensory stimulation. Evidence for and rationales behind different sensory therapies will be discussed below. It is worth emphasising that sensory interventions may not only be part of a specific “therapy” but may have a role in orientating people with dementia and minimising distress from confusion. Good practice of caring for patients with dementia includes furnishing them with appropriate sensory aids (glasses, hearing aid) and maintaining orientation with appropriate lighting for the time of day, along with prominent windows, clocks and calendars. The different senses and their role in the management of dementia will be considered in turn. 4.1. Vision As well as their role in orientation, glasses and adequate lighting are necessary for reducing the risk of falls in dementia. Lighting plays a key role in the co-ordination of biological and psychological processes in the body, many of which are entrained to the individual’s circadian rhythm which is influenced by light detection and subsequent melatonin secretion. Many elderly people are not exposed to high enough luminance levels to maintain the circadian rhythm, due to a combination of lack of time spent outdoors, poorly lit indoor environments, and increased opacity of the lens leading to reduced transmittance of light [40]. Disruption to the circadian pacemaker, located in the suprachiasmatic nucleus of the hypothalamus, due to insufficient light stimulus [41] or degenerative change [42] may result in unstable circadian patterns and subsequent cognitive, mood, and behavioural disturbances. “Light therapy” has been proposed as a strategy for maintaining a stable circadian rhythms by stimulating the suprachiasmatic nucleus. This has been attempted by both increasing ambient light in care facilities [43] and exposure to timed bright light [44]. A Cochrane review examining both practices found no significant evidence that light therapy improved sleep, cognition or behavioural and psychiatric symptoms in patients with dementia [42] but acknowledged that the meta-analysis was constrained by a dearth of good quality trials. A subsequent meta-analysis [45] concludes that light therapy is effective in improving sleep, depression and agitation in older adults with dementia and goes as far as to propose a 24-h lighting scheme to improve circadian rhythm entrainment and reduce the risk of falls, although this is yet to be evaluated by controlled trial. Light therapy has also been trialled in conjunction with melatonin therapy [41]; the authors concluded that increasing illumination levels improved cognitive, mood, sleep and behavioural symptoms in patients with dementia and that melatonin improved sleep, but cautioned that melatonin should only be used in conjunction with light, as the light therapy seemed to ameliorate the adverse effects that melatonin had on mood. 4.2. Hearing As mentioned above, hearing aids are important to orient people with dementia. Hearing loss has an impact on the quality of life in older adults, in particular, it is associated with a significant impairment of measures of activities of daily living (ADLs) [46]. Older people with hearing loss may compensate by a combination of extrapolation from what little is heard, lip reading, and increased attention, but a decline in cognitive function constrains this. There is the risk that hearing aids will be unacceptable to people with dementia, as they may be unable to compensate for

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the indiscriminate magnification of background noise [40] and to adjust the settings appropriately. However, hearing aids may reduce the risk of sensory deprivation [47] and have been shown to be acceptable to patients with dementia and their caregivers. Although they do not improve cognitive functioning and psychiatric symptoms in patients with dementia, it has been shown that they can improve global measures of functioning such as the Clinical Global Impression of change (CGI) scale [48]. Music may have a therapeutic effect on people with dementia, whether this is just by listening to, playing, or dancing to music or by engaging in “music therapy” with a trained therapist. Memory for music seems robust and may be demonstrated long after other memories and abilities have declined [49]. It is possible that prompting such recall (through singing or dancing) may promote a sense of competency and well-being in patients with dementia and enable them to interact meaningfully with others [50]. Autobiographical recall has also been shown to be improved with background sound, when compared with silence, with music being also more effective than meaningless noise [51]; it may be beneficial to use music to aid information gathering when interviewing a patient with dementia. The mechanism of the effect of music on behavioural and psychological symptoms of dementia has not been established. It has been suggested that a reduction of cortisol may alleviate some of the anxiety symptoms [50], or music may act as a positive distractor and regularity and predictability of the stimulus settles agitated and “arrhythmic” behaviour [49]. 4.3. Smell NICE recommends the use of aromatherapy for behavioural and psychological symptoms of dementia [39], although it has been pointed out that, as olfaction tends to decline in dementia, this may not be an appropriate intervention [52]. The use of aromatherapy (particularly lavender and lemon balm) in dementia is widespread, with much case-based evidence for positive effects in sleep and agitation; however, there is a lack of high-quality trials in the field [53]. It is also worth noting that in many cases the aromatherapy is administered by a therapist and often by some form of physical contact such as massage, which may have an additional therapeutic value. It is possible that the strong link between smells and emotion mediates some of the response to aromatherapy. The olfactory bulb links to the amygdala and thus some smells may trigger positive or negative emotional states depending on the person’s past experience of the smell [53]. Pharmacological theories of aromatherapy have also been proposed, where the direct action of the compounds on the brain are thought to mediate the effect, with perception of the odour not being required [53]. This theory may explain why aromatherapy works for people with dementia, who may have an impaired sense of smell. 4.4. Touch Touch is a vital component of caring for any dependent person; however, the form of touch used in everyday care tends to be “instrumental” (i.e. as “part of a technical or physical task”) rather than “expressive”, which is more emotional (i.e. holding a patient’s hand) [54]. A Cochrane review found that “the very limited amount of reliable evidence is in favour of massage and touch interventions for problems associated with dementia” [55], even though the need for expressive touch in dementia has been suggested for decades [56]. The evidence there is tends to focus around hand massage or the addition of touch to verbal encouragement to eat, and interventions involving touch often also involve another sensory modality, i.e. by combining massage with music or aromatherapy [55].

There has been little research emphasis on the mechanism by which massage and touch improves symptoms for any condition [57], but one could hypothesise, that touch may enable a non-verbal communication, when perhaps the patient does not have the cognitive function to comprehend a verbal message. Touch may also be the only way a patient with dementia may identify they are receiving attention and recognition from others, which may improve their self-esteem and sense of well-being [54]. 4.5. Taste Altered food preference and a tendency to prefer sweet food has been demonstrated in dementia [58]. Given the prevalence of nutritional deficiencies in patients with dementia, it may be prudent to offer sweetened foods in order to maximise nutritional intake, and perhaps specific oral nutritional supplements may be designed in the future to be more appealing to patients with dementia. 5. Multisensory stimulation Multisensory stimulation or “Snoezelen” is a therapy developed in the field of learning difficulties and involves the stimulation of multiple senses by the patient’s exploration of an environment including light effects, calming sounds, smells and tactile stimulation. The variations in clinical practice and research protocol of Snoezelen for dementia make the assessment of the therapeutic value difficult to establish in meta-analysis, which in turn impedes the development of the therapy [59]. A Cochrane review of 4 studies found insufficient evidence to make any recommendations [59] but a subsequent meta-analysis of 18 studies [60] found immediate positive effects on behaviour and mood of people with dementia and called for more reliable protocols to be used in future trials. A small study looking at interactions between patients and carers during the morning care regime found that training carers in Snoezelen improved communication and reduced negative behaviour, even though the interaction was not a “therapy” as such or conducted in a specific multisensory environment [61]. Various theories have been proposed for Snoezelen’s mechanism of action. Kovach suggests that older adults with dementia experience an imbalance of sensory input due to prolonged periods of lack of stimuli or sensory deprivation, and other periods of high-stimulus (i.e. in a large, noisy communal room). She proposes that this imbalance (or lack of “sensoristasis”) leads to discomfort which presents as agitation and decline in social and cognitive function [62]; Snoezelen may address this imbalance and alleviate discomfort. A key feature of Snoezelen is the interactivity and the environmental response to the patient’s actions. Patients with dementia are likely to not have much control over their environment and therefore this sense of control may improve their self-esteem and confidence. The environment is also “demandfree” and does not require any cognitive processing, contrary to many other activities a patient with dementia may be offered; this may be a welcome relief and therefore improve well-being. The role of the care-giver or therapist is also likely to be significant, and being able to share an experience may reduce feelings of isolation. The evidence of improved communication following care-giver training in Snoezelen [61] suggests that benefits may be mediated by the style of interaction rather than requiring specific sensory equipment. 6. Technology and building for the sensory experience of dementia People with dementia are very sensitive to changes in environmental conditions [40]. For example, a rise in temperature can

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trigger requests for attention, and an increase in ambient noise levels can decrease the prevalence of strange movements [40]; this may be due to perceptual disturbance or due to difficulties processing sensory input. Environmental factors have been shown to correlate with quality of life [63], and there is a negative relationship between quality of life and buildings that are designed to prioritise health and safety [64]. Some sensory technology that may be useful in theory, such as lights that turn on by motion sensor to guide people to the bathroom at night [41], may be confusing and distressing to some people with dementia [40]. Therefore, a careful balance must be struck to use technology appropriately to maintain a comfortable and understandable environment and to keep patients safe without negatively affecting their quality of life. 7. Conclusion The association between sensory impairment, the diagnosis of dementia and the role of sensory therapy in its management has been recognised for a long time, but has not been the focus of concerted research; current understanding is patchy due to small numbers of underpowered and heterogeneous studies. With the ageing population and rising prevalence of dementia, there is widespread interest in markers of early signs of dementia and tests to identify which patients with MCI will progress to dementia. It is possible that some form of sensory test may contribute to such information. Similarly, the move away from the use of antipsychotic medication for BPSD and the rise of purpose-built dementia homes may raise the profile of sensory considerations in the management of dementia. Sensory processing difficulties are well recognised in neurodevelopmental conditions (e.g. Autism Spectrum Disorders) and there is a move towards creating individual sensory profiles in order to inform management plans [65]; perhaps similar strategies will be indicated in the future for the management of BPSD (Box 1).

Box 1 A summary of some of the sensory-related considerations when designing and managing living spaces for people with dementia [40,62] Olfactory 1. 2. 3. 4.

Use perfumed soaps when washing. Fragrant (non-poisonous) plants and flowers in living areas. Avoid potpourri (may appear to be edible). Kitchen adjacent to dining room-cooking smells will aid orientation, and improve appetite and food intake. 5. Alarms for detection of smoke, gas and fire and to alert people if the fridge has been open too long and food may be perishing. Visual 1. Adequate lighting to maintain circadian rhythm, reduce risk of falls, etc. but not too bright to be distressing. 2. Avoid highly polished floors – glare can be distressing. 3. Avoid too many shadows, which can be distracting and frightening. 4. Open floor plans for access to daylight and improved sight lines. 5. Easy access to outdoor space. 6. Avoid flickering lights (risk of agitation and seizures). 7. Light switches by bed and at door. 8. Heavy curtains to keep light out at night. 9. Avoid highly-patterned rugs or flooring-can be confusing and distracting.

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Sound 1. Smaller rooms to avoid excessive background noise but some background music or noise aids concentration. 2. Avoid background TV-can be misinterpreted as real. 3. Automatic fans/ventilation systems may be distressing and distracting. Touch/temperature 1. Upholstery and flooring materials should be easy to clean but have a “homely” feel. 2. Windows should be easy to open (but not open so wide to risk accident). 3. Clothing should be easy to remove, while maintaining dignity. 4. Set thermostats to only operate within a comfortable temperature range, but having an accessible and visible thermostat increases autonomy. 5. Underfloor heating good to increase circulation to extremities and avoid burns from contact with radiators or hot water pipes.

Contributors and their role Sophie Behrman – First draft (part), revisions (whole). Leonidas Chouliaras – First draft (part), revisions (whole). Klaus P. Ebmeier – First draft (part), revisions (whole). Competing interest Sophie Behrman – none; Leonidas Chouliaras – none; Klaus P. Ebmeier – reports consultation fees received from Lily in relation to Amyvid TM. Funding Leonidas Chouliaras – National Institute for Health Research – Academic Clinical Fellow. Klaus P. Ebmeier – UK Medical Research Council (G1001354), the Gordon Edward Small’s Charitable Trust (SC008962), and the HDH Wills 1965 Charitable Trust. Provenance and peer review Commissioned and externally peer reviewed. Acknowledgements SB is Core Trainee in Psychiatry, LC a NIHR-funded Academic Clinical Fellow. References [1] Arlinger S. Negative consequences of uncorrected hearing loss – a review. International Journal of Audiology 2003;42(Suppl. 2):2S17–0S. [2] Weinstein B. Hearing loss and senile dementia in the institutionalized elderly. Clinical Gerontologist 1986;4(3):3–15. [3] Herbst KG, Humphrey C. Hearing impairment and mental state in the elderly living at home. British Medical Journal 1980;281:903–5. [4] Uhlmann RF, Larson EB, Rees TS, Koepsell TD, Duckert LG. Relationship of hearing impairment to dementia and cognitive dysfunction in older adults. JAMA: The Journal of the American Medical Association 1989;261:1916–9. [5] Gates GA, Beiser A, Rees TS, D’Agostino RB, Wolf PA. Central auditory dysfunction may precede the onset of clinical dementia in people with probable Alzheimer’s disease. Journal of the American Geriatrics Society 2002;50:482–8. [6] Gates GA, Cobb JL, Linn RT, Rees T, Wolf PA, D’Agostino RB. Central auditory dysfunction, cognitive dysfunction, and dementia in older people. Archives of Otolaryngology – Head & Neck Surgery 1996;122:161–7.

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