In this commentary, it is argued that the definition of the time or the age variable in the models presented by Hofer and Sliwinski is ambiguous, and a standard interpretation of this time of age variable is proposed instead. Some simulation studies are presented, the results of which indicate that, even with age-heterogeneous cross-sectional data, correct identification of the true sources of age-dependent variation is possible. An important qualification, based on new methodological work in progress, is given of the scope of longitudinal designs. It is concluded that all kinds of age-related changes are potentially interesting and can be correctly identified and explained.
All Science Journal Classification (ASJC) codes
- Geriatrics and Gerontology