Time-of-Day Variations in Narrative Discourse in Normal Aging and Alzheimer ’ s Disease

Purpose: The purpose of this study was to investig ate whether language discourse followed a diurnal pattern across one 10-hour day i n normal healthy aging individuals (NHA) and individuals with mild to moderate Alzheim er’s disease. Method: 10 normal healthy aging (NHA); and 10 olde r adults clinically labeled with probable Alzheimer’s disease (AD) were recruited fo r this study. Measurements of language and cognition were collected across one da y at 9:00am, 12:00pm, 3:00 pm, and 6:00pm. Language samples were evaluated for quanti ty and quality, mazes, abandoned utterances, total utterances, type token ratio, and wor s per minute. Results: The NHA group performed significantly bet ter on cognitive measures across the day than the AD group; cognitive performance was no t correlated with any of the linguistic measures. Measures of narrative quality were significantly different between the groups with AD participants producing significa ntly more abandoned utterances. Diurnal effects appeared most prevalent in the NHA group, with declining performance across the day, while the AD group showed less vari ation across the day. Conclusions: These findings suggest that some aspe cts of language are susceptible to changes in circadian rhythms, thus impacting therap eutic outcomes and diagnostic presentation. Running Head: TIME-OF-DAY AND DISCOURSE IN AGING AND AD 3 INTRODUCTION Language changes have been reported in normal healt hy aging, while language impairments have been reported for those with in Al zheimer’s disease (AD). Researchers have found conversational discourse impairments in propositional content, grammatical complexity, syntactic complexity, naming, cohesion, coherence, and length in both healthy aging and in individuals with AD when compa red to younger persons (Bayles and Tomoeda, 2007; Kemper, Thompson, & Marquis, 200 1; Bowles & Poon, 1985; Drevenstedt & Bellezza, 1993). Researchers investig atin discourse in individuals with AD and those with mild cognitive impairment have re ported deficits including vague and empty language content, disruptions in cohesion and coherence, difficulties with turntaking, decreases in number of utterances and total w rds, increases in use of mazes (i.e., a series of words that do not contribute to the mea ning of language), and verbosity (Flemming & Harris, 2008; Dijkstra, Bourgeois, Alle n, & Burgio, 2004; Carlomagno, Santoro, Menditti, Pandolfi, & Marini, 2005; Cherne y & Canter, 1990; Glosser & Deser, 1990; Nicholas, Obler, Albert, & Helm-Estabrooks, 1 985; Hier, Hagenlocker, & Schlindler, 1985). The number of people diagnosed with AD in the US is predicted to reach 7.7 million by 2030, a more than 60% increase from the 5.1 million currently affected (Alzheimer’s Association, 2010). Therefore, identi fying factors that contribute to cognitive and language change, is imperative to und erstanding healthy aging individuals and those with AD. The current study looks specifically at language th rough the lens of spoken language discourse which refers to conversations or larger units of talking such as stories Running Head: TIME-OF-DAY AND DISCOURSE IN AGING AND AD 4 or songs (Guendouzi & Muller, 2007). A specific ty pe of discourse is narrative discourse that involves the recounting of an event or series of events in chronological order. Narratives are an important aspect of communication , as they often are used for entertaining, and are essential for social communic ation. Production of narrative discourse requires the comp lex interface of linguistic, cognitive, and social abilities (Coelho, 1995). Nar ratives frequently have been studied, because they are considered a formulaic type of dis cour e due to their predictable structure. Such narratives follow a cognitively ba sed, measurable, structured set of rules called story grammar, which are not dictated by the sp cific content of the message conveyed (Coelho, 1998). Recent interest in age-re lated changes has led to an increase in the number of investigations of the interaction amo ng aging, discourse, and cognition. Cannizzaro and Coelho (2003) investigated the relat ionship between discourse and executive function by using narrative samples from healthy aging adult ages 18-98. Using story generation and story retelling, the res ults indicated that like previous studies, the elderly performed the poorest, and deficits wer e noted even in the highly educated. Furthermore, the authors reported a relationship be tween story grammar and measure of executive function in aging, where increasing age w as correlated with decreasing grammar quality (Cannizzaro & Coelho, 2003). The a uthors suggested that investigating narrative performance might provide a more suitable scale to treat and assess performance of those with cognitive-communication d ifficulties as opposed to more targeted impairment-based treatments and assessment s. Running Head: TIME-OF-DAY AND DISCOURSE IN AGING AND AD 5 Studies previously investigating discourse in indiv iduals with dementia have reported numerous deficits. (Cherney & Canter, 1990 ; Glosser & Deser, 1990; Nicholas,