Thank you very much for that question.
It does seem counterintuitive that the person who is spending most of his or her time with that patient would not be the one who necessarily knows the patient the best, but this has been shown in research.
One study that I referenced in my original statement submission was a geriatric psychiatry paper where 91 people with mild to moderate dementia were paired with their primary caregivers, most of whom were spouses or lived with the patient. They were asked to fill out a quality-of-life survey. The same quality-of-life questionnaire was given to the patients and the caregivers. Because the patients were still mild to moderate, they were able to answer questions.
There were five domains in this. One was self-esteem or how they feel about themselves as a person. Another was positive affect, which is whether they are mostly happy. Another was negative affect: Did they have anxiety, depression, sadness or guilt? Also, what was their feeling of belonging? Did they feel that they had a part in society? Did they feel that they were a part of a cadre of people who cared for them? Finally, it was the sense of aesthetics, which referred to their ability to attain pleasure in life.
They found that the agreement between the patients filling out the questionnaire and their caregivers was not very good.
Another thing they looked at was caregiver burden. They asked the caregiver how much stress they felt with their job. They also did a survey of how dependent the patients were. Over 50% of the patients needed hands-on care at that point and 44% of them had behavioural issues, such as paranoia or some aggressive tendencies. The thing that correlated the best with the disagreement was caregiver burden. If the caregiver felt extreme burden in their care, they may have been projecting their feelings onto the quality of life of the patient, whereas the patient may have felt that their quality of life was actually quite good.
I hope that answers your question.