Aim To investigate whether narrative discourse followed a diurnal pattern across one ten-hour day in healthy ageing people and those with mild to moderate Alzheimer’s disease (AD).

Method Ten healthy ageing people and ten clinically labelled with probable AD were recruited. Measurements of language and cognition were collected across one day at 9am, 12pm, 3pm and 6pm. Language samples were evaluated for quantity (total utterances and words per minute) and quality: mazes or fillers, repetitions and revisions, abandoned utterances and type token ratio or percentage of different words to total words.

Results The healthy ageing group performed significantly better on cognitive measures across the day than the AD group. At all times the healthy ageing group produced significantly longer narrative samples that were significantly less aborted and revised than the AD group. Additionally, both groups demonstrated declining narrative performance as the day progressed.

Conclusion Based on these results, time of day may be an additional factor that moderates narrative performance. This change in narrative ability may have an effect on making a proper diagnosis, therapeutic effectiveness and patient interactions, therefore affecting quality of care.