On the preservation of syntax in Alzheimer's disease. Evidence from written sentences.

We examined the syntactic complexity of single written sentences elicited from 368 adults undergoing examination for possible Alzheimer's disease. The clause length and composition of the sentences varied with the severity of dementia. The nondemented adults' sentences contained more propositions, main and secondary verbs, and conjunctions than those produced by the mildly and moderately demented adults. Sentence length in clauses, propositional content, and the use of conjunctions and main and secondary verbs discriminated among stages of the severity of the disease. The present results suggest that, while dementia severity affects written linguistic output, such output is, nonetheless, grammatic and coherent.