Considering the senses in the diagnosis and management of dementia.

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.