The objective of this Annex-study is to explore the feasibility and validity of Health Related Quality of Life (HRQL) value measurement in dementia patients. And to study the characteristics of proxy rating in HRQL research in dementia and the suitability and validity of yielding HRQL measurements by proxy assessment. Furthermore to explore the validity, reliability, and feasibility of the EQ5D and EQ6D in dementia research (in patients and in/by proxies); response shift, and alternative (more simple) methods of HRQL measurement and validate the Dutch versions of the QOL-AD and the use of the CarerQol-7D in dementia research.