A most challenging task for scientists that are involved in the study of ageing is the
development of a measure to quantify health status across populations and over time. In the
present study, a Bayesian multilevel Item Response Theory approach is used to create a
health score that can be compared across different waves in a longitudinal study, using
anchor items and items that vary across waves. The same approach can be applied to
compare health scores across different longitudinal studies, using items that vary across …