Language Abnormalities in Alzheimer’s Disease Arise from Reduced Informativeness: A Cross-Linguistic Study in English and Persian

INTRODUCTION This research investigates the psycholinguistic origins of language impairments in Alzheimer’s Disease (AD), questioning if these impairments result from language-specific structural disruptions or from a universal deficit in generating meaningful content.

Cross-linguistic analysis was conducted on language samples from 184 English and 52 Persian speakers, comprising both AD patients and healthy controls, to extract various language features. Furthermore, we introduced a machine learning-based metric, Language Informativeness Index (LII), to quantify informativeness.

Indicators of AD in English were found to be highly predictive of AD in Persian, with a 92.3% classification accuracy. Additionally, we found robust correlations between the typical linguistic abnormalities of AD and language emptiness (low LII) across both languages.

Findings suggest AD linguistics impairments are attributed to a core universal difficulty in generating informative messages. Our approach underscores the importance of incorporating biocultural diversity into research, fostering the development of inclusive diagnostic tools. Competing Interest Statement The authors have declared no competing interest. Funding Statement This work was supported by Alzheimer's Association Clinician Scientist Fellowship (AACSF) 2022A015154 and MGH Screening Technologies in Primary Care Innovation Fund (PCIF) 2023A063002, as well as National Institutes of Health grants R21 DC019567, R21 AG073744, and R01 NS131395. Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: The research section of the Persian cohort was approved by the ethics committee of Iran University of Medical Sciences, which governs human subjects research in accordance with their guidelines. All participants provided written informed consent to participate in this study. We certify that the study was performed in accordance with the ethical standards as laid down in the 1964 Declaration of Helsinki and its later amendments. This study particularly champions biocultural diversity through the inclusion of participants from two linguistically and culturally distinct cohorts, thereby advancing the principle of avoiding ethnocentric biases in human data collection. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data Availability All English samples are available through Dementia Bank which is publicly accessible. The Persian samples can be accessed through a reasonable request to the senior author of the manuscript at nrezaii{at}mgh.harvard.edu.