Doctors will sometimes use "benevolent deception" 
when dealing with patients who have dementia


"Truthfulness is the foundation of the doctor-patient relationship… But there are limitations and
pitfalls to this process:"

Patient: Doctor, I know I can still drive. Just let me take a test.

Doctor A: I’m sorry, Mr. K, but I can’t help you with that. As we
discussed, your memory impairment makes it unsafe for you to drive.

Patient: Just let me take the test. I can drive just fine.

Doctor A: The memory testing tells us that you would not be a safe driver.

Patient: My memory is not that bad. I know I can drive.

Patient’s wife: Honey, I told you that the car is not working now and needs to be fixed. Let’s talk about it later.

Patient: Okay.

"Mr. K’s wife did what caregivers for individuals with dementia often
do — she placated his concerns for the moment and then redirected him,
in essence telling a lie. Should doctors ever do the same thing?"

Read more in this short essay on doctor / patient ethics: The Benevolent Deception: When Should a Doctor Lie to Patients? The Atlantic>>
 
– How We Age: A Doctor’s Journey Into the Heart of Growing Old by Marc E. Agronin>>
– Detail from Leonardo Da Vinci’s Study of an Old Man, Da Vinci Gallery>>