Is There a Language Prodrome for Alzheimer's Disease? A Clinical Perspective

With the growth in the aging population and the concomitant rise in the prevalence of Alzheimer’s disease (AD), the need to define changes in cognitive functioning at the earliest stages, prior to disease onset, when treatments are likely to be most effective, has become increasingly important. In addition to the advent of biomarkers that can now detect early pathological changes associated with AD through imaging and cerebrospinal fluid analysis, subtle changes in cognition may also be present at these prodromal stages. While investigations to date point to early changes in episodic memory, recent research, including results from our studies, suggests that subtle changes in language may also be evident at preclinical stages of AD. Within this paper, I describe results of these studies and discuss how changes in language might best be identified within a clinical setting.

Our research focuses on determining whether changes in language distinguish healthy older individuals from those with Mild Cognitive Impairment (MCI), a known precursor of AD in which there is evidence of cognitive decline, but without dementia. Our findings suggest that individuals with MCI may have more difficulty integrating syntax and semantics, impacting their ability to precisely and effectively convey meaning. Our findings suggest that the language changes cannot be accounted for by a decline in memory. I relate our findings to case studies that have examined language in individuals prior to a diagnosis of AD, as well as findings from group studies that identify a breakdown in semantic memory in pre-clinical stages. The findings from these studies cohere and suggest that there may be an early breakdown in efficient access to semantic knowledge and its integration with syntax. I provide examples of these changes and how they are distinguished from the changes in language that accompany normal aging.

I discuss possible methods to identify changes in language within a clinical setting and the need to understand what changes in language are ‘normal’ vs. those that may herald AD. I address the challenge associated with how variations in language abilities within a normal population may impact presentation of language changes in prodromal AD. Finally, I consider what factors may help to preserve language function. Specifically, one goal of our future research is to determine whether engagement in language-based activities, including reading, writing and social activities may serve as protective factors for dementia.