Which of the following statements from a client's son would best support a diagnosis of delirium?

The statement from the client's son that indicates the change in behavior occurred rapidly is significant in supporting a diagnosis of delirium. Delirium is characterized by an acute onset of confusion, altered consciousness, and cognitive disturbances, which can develop over hours to days. The sudden appearance of these symptoms is a hallmark of delirium, distinguishing it from other cognitive disorders that typically manifest more gradually.

In contrast, the other statements do not strongly indicate delirium. The mention of long-standing forgetfulness and confusion suggests a more chronic cognitive issue, potentially pointing to conditions like dementia, which develops slowly over time. The acknowledgment from the doctor regarding temporary conditions indicates that there's a possibility of a non-permanent problem, which may not align with the acute nature of delirium. Lastly, increased sleep alone does not provide specific evidence of delirium, as many factors can contribute to changes in sleep patterns that are not necessarily linked to acute cognitive disturbances. These factors highlight the importance of the rapid change in behavior as the most compelling evidence for a diagnosis of delirium.