Various cognitive functions, such as memory, language, and executive functions, gradually deteriorate over time in patients with dementia (PWD). Communication is regarded as the process by which information is shared between persons. The information sender conveys his or her intentions while the information receiver speculates these intentions by integrating verbal and nonverbal information based on the situation and context. Therefore, besides language, communication requires various cognitive functions. During the early stages of the disease, PWD do not experience severe language dysfunctions, but their communicative abilities begin to decline during this stage due to other cognitive dysfunctions.
 This article aimed to review approaches for supporting augmentative and alternative communication (AAC) in PWD, depending on the severity of the disease. Also, it was reviewed on the characteristics of language and cognitive functions in dementia as well as relationships between language and cognitive functions during communication, in terms of implications for interventions aiming to improve communication in severe PWD.
 In the late stages of dementia, as cognitive dysfunction worsens, assessing the effect of each cognitive function (including language) on communicative abilities becomes more difficult. Interventions based on these cognitive assessments are also challenging. In contrast, nonverbal communication or the desire for mutual communication is reported to be relatively preserved in patients with severe dementia. This is important for establishing an effective intervention that would allow for interpersonal interactions.
 Deterioration of communicative abilities in severe PWD also affects decision making. In such cases, family caregivers undertake proxy decision-making by speculating the PWDs' desire. However, this may burden the family. These problems occur due to the lack of information. PWDs in the late phase of the disease may find it difficult to communicate their feelings; thus, there is a lack of information for proxy decision-making.
 AAC is basically the way to augment verbal language. There are a few reports on AAC for PWD in which a memory book, which records past experiences with pictures and explanatory sentences, served as an effective tool for communication, as it compensated for PWDs' memory decline. In this article, this form of AAC for PWD prove to be an effective tool for both communicating and obtaining basic information for proxy decision-making, as it helped family caregivers understand PWDs' view of life with the aid of a memory book, though further study is necessary to adapt in clinical settings. In the last stage of dementia when most PWD are unable to convey their wishes verbally, owing to which they cannot make decisions, it is speculated that AAC in the form of a memory book could help track events in PWDs' lives, which in turn would serve as basic information for proxy decision-making.
 Author's abstract