In dementia in inflecting and agglutinating languages, morphosyntax is much better preserved than lexical access or pragmatics, but little is known about how dementia affects language in polysynthetic agglutinating languages with their complex verb morphology. Fortuitously, a series of narratives by a skilled Arapaho storyteller includes sessions from late in his life, when he was evidently dementing. Verb forms and clausal connectors in the speaker’s Arapaho predementia and dementia narratives were sorted computationally and analyzed statistically. We found a decline in subordination and an increase in utterances missing verbs. There was a shift from using transitive active verb forms toward impersonal and passive verb forms, which require less pragmatic and syntactic computation to deploy, and a shift in subordination markers away from those requiring explicit consideration of the temporal relations between clauses.