Introduction

The following exercise is a case study of a woman (‘Martha’) aged 87 years who was studied by Hydén and Örulv (Reference Hydén and Örulv2009). At the time of study, Martha had had a diagnosis of Alzheimer's disease for four or five years and was living in a residential care unit. The case study is presented in five sections: primer on Alzheimer's disease; language in Alzheimer's disease; focus on language in Alzheimer's disease; discourse in Alzheimer's disease; and focus on discourse in Alzheimer's disease.

Primer on Alzheimer's disease

Alzheimer's disease (AD) is the foremost cause of dementia worldwide, accounting for up to 75% of all dementia cases (Qiu et al., Reference Qiu, Kivipelto and von Strauss2009). This neurodegenerative disorder manifests as progressive memory impairment followed by a gradual decline in other cognitive abilities which lead to complete functional dependency (Rafii and Aisen, Reference Rafii and Aisen2015). In a systematic review of data from Europe and the US published between January 2002 and December 2012, Takizawa et al. (Reference Takizawa, Thompson, van Walsem, Faure and Maier2015) reported that the prevalence of AD ranged between 3% and 7%. The annual incidence of AD is increasing, with an incidence of 377,000 new cases in the US in 1995 expected to increase to 959,000 cases in 2050 (Hebert et al., Reference Hebert, Beckett, Scherr and Evans2001). There are two different forms of AD based on age of onset and genetic pre-disposition. Sporadic or late-onset AD accounts for over 95% of cases and begins after the age of 65 years. Early-onset or familial AD is rare and usually manifests before 60 years of age (Bali et al., Reference Bali, Gheinani, Zurbriggen and Rajendran2012). The two primary lesions associated with AD are neurofibrillary tangles and amyloid plaques. These are abnormal proteins which accumulate inside neurones in the case of neurofibrillary tangles and in the spaces between nerve cells in the case of amyloid plaques. A further morphological alteration in AD is the loss of synaptic components (Perl, Reference Perl2010).

Alzheimer's disease is an underlying pathology in many of the clients who are assessed and treated by speech-language pathologists. This is because these clients can present with considerable speech, language, cognitive and swallowing problems. The motor speech disorders apraxia of speech and dysarthria are a feature of AD. Cera et al. (Reference Cera, Ortiz, Bertolucci and Minett2013) reported significantly lower scores for speech and orofacial praxis in 90 individuals at different stages of AD than in normal controls. Spastic dysarthria has been reported in two children and their mother, all of whom experienced early-onset familial AD in their 30s (Rudzinski et al., Reference Rudzinski, Fletcher, Dickson, Crook, Hutton, Adamson and Graff-Radford2008). Aphasic and non-aphasic language impairments are present in AD. Ahmed et al. (Reference Ahmed, Haigh, de Jager and Garrard2013) analysed connected speech samples from 15 patients with autopsy-confirmed AD using measures of syntactic complexity, lexical content, speech production, fluency and semantic content. Subtle language changes were evident during the prodromal stages of AD. There were significant linear trends in syntactic complexity and semantic and lexical content over the prodromal, mild and moderate stages of disease. Cognitive deficits in clients with AD range from mild cognitive impairment in the prodromal stage of disease to increasingly severe forms of dementia with disease progression (Ward et al., Reference Ward, Tardiff, Dye and Arrighi2013). Swallowing is problematic for individuals with AD and not just for those with late-stage disease. Priefer and Robbins (Reference Priefer and Robbins1997) reported significantly increased oral transit duration, pharyngeal response duration and total swallow duration in individuals with mild-stage AD relative to healthy, elderly controls.

Language in Alzheimer's disease

Alongside other cognitive functions, language is disrupted with the onset and progression of Alzheimer's disease. Language impairments in AD are wide-ranging in nature, and can take the form of an aphasia syndrome or a non-aphasic language disorder. Cummings et al. (Reference Cummings, Benson, Hill and Read1985) examined 30 patients with dementia of the Alzheimer type, and found aphasia in all patients. The language disorder resembled a transcortical sensory aphasia. Murdoch et al. (Reference Murdoch, Chenery, Wilks and Boyle1987) examined the language profile of 18 patients with Alzheimer's disease. On a standard aphasia test battery, these patients scored significantly lower than non-neurologically impaired control subjects in the areas of verbal expression, auditory comprehension, repetition, reading and writing. The language disorder of these patients resembled a transcortical sensory aphasia. Semantic abilities were impaired while syntax and phonology were relatively intact. That language subsystems deteriorate at different stages in AD is confirmed in a review of studies of language impairment by Emery (Reference Emery2000). Emery reported a negative relation between sequence in language development and language decline. Specifically, language forms which are learned last in the sequence of language development and are most complex are the first to deteriorate in AD.

Alzheimer's disease pathology is also associated with primary progressive aphasia (PPA), a neurodegenerative disorder in which language impairment is the primary feature. A form of PPA called logopenic/phonological aphasia is most often related to AD pathology. Rohrer et al. (Reference Rohrer, Rossor and Warren2012) examined the language features of 14 patients with PPA and confirmed AD. These patients exhibited relatively non-fluent spontaneous speech, phonemic errors and reduced digit span. Verbal episodic memory was also impaired in most patients.

Focus on language in Alzheimer's disease

To illustrate some of the language problems that occur in Alzheimer's disease, this unit will examine the conversational discourse of a woman called Martha. Martha had had a diagnosis of AD for four or five years at the time of study. She is still in a relatively early stage of the disease. Martha has word-finding problems and some difficulty tracking the referents of terms, particularly pronouns. However, she is able to handle these problems by using circumlocutions and semantically related words as well as some formulaic language. She rarely uses neologisms. Martha is telling Catherine, an 88-year-old resident of the care unit, about her former experience of learning to drive, purchasing a car and taking the family on a long car journey one summer. Catherine has had a diagnosis of AD for seven or eight years. Her role in the storytelling is largely that of a confidante to Martha.

Discourse in Alzheimer's disease

Aside from structural language problems in Alzheimer's disease, clients with AD can also experience considerable pragmatic and discourse deficits. Often, these deficits emerge earlier than structural language impairments. Their combined effect is to reduce the communicative effectiveness of the speaker with AD. In terms of pragmatics, clients with AD exhibit deficits in the comprehension of all forms of non-literal language. This includes the comprehension of metaphors (Roncero and de Almeida, Reference Roncero and de Almeida2014), idioms (Rassiga et al., Reference Rassiga, Lucchelli, Crippa and Papagno2009), proverbs (Leyhe et al., Reference Leyhe, Saur, Eschweiler and Milian2011) and sarcasm (Maki et al., Reference Maki, Yamaguchi, Koeda and Yamaguchi2013). Impaired understanding of non-literal language explains the evident difficulties with humour appreciation and social communication in individuals with AD. Aspects of politeness facework are disrupted in clients with AD (Rhys and Schmidt-Renfree, Reference Rhys and Schmidt-Renfree2000). Individuals with AD also have difficulty contributing relevant, informative utterances to conversation and other forms of discourse (Dijkstra et el., Reference Dijkstra, Bourgeois, Allen and Burgio2004; St-Pierre et al., Reference St-Pierre, Ska and Béland2005).

Among discourse deficits in AD are referential disturbances. Clients with AD are unable to ground reference in the shared knowledge and experience of their communicative partners (Feyereisen et al., Reference Feyereisen, Berrewaerts and Hupet2007). This makes narrative and other forms of discourse particularly difficult to follow as expressions such as demonstratives can lack clear referents. Topic management is also compromised in AD, with clients displaying a reduced ability to change topics whilst maintaining discourse flow and difficulty in contributing to the propositional development of a topic (Mentis et al., Reference Mentis, Briggs-Whittaker and Gramigna1995). Discourse cohesion and coherence are impaired in AD. Ripich et al. (2000) reported a significant decline in the use of ellipses and conjunctions in 23 subjects with early to mid-stage AD over time. Pragmatic and discourse deficits in AD have been related to theory of mind impairments and executive dysfunction (see chapter 3 in Cummings (Reference Cummings2014b) for discussion of the cognitive basis of these deficits).

Focus on discourse in Alzheimer's disease

To illustrate some of the discourse deficits (and strengths) that are found in clients with AD, it is useful to return to Martha's narrative about learning to drive a car. The extract that follows is preceded by Martha describing her husband's doubts about her driving and his questioning of her ability to drive. Before the extract begins, Martha relates how she told her husband and her children that she was to take the driving test the following day. On this occasion, Martha and Catherine are joined by a nurse at the care unit as well as another resident called Niels.