Fig. 2.

Association between age at diagnosis and severity of joint damage in five longitudinal cohorts summarized in a meta-analysis (a) and depicted for patients with rheumatoid arthritis included in the Leiden Early Arthritis Clinic (EAC) for different age categories (b). a Age was entered as a continuous variable in the multivariate normal regression analysis, because the plots of the raw data suggested no interaction of age with time. The meta-analysis (inverse weighted meta-analysis with a random-effect model) summarizes the effects of the age of the different cohorts. An effect size of 1.034 represents a 1.034-fold increase in joint damage per year increase in age. Because these effect sizes were unit-free they could be compared in meta-analysis. b Although age was analyzed as a continuous variable, the predicted Sharp-van der Heijde (SHS) scores per age-category were plotted to illustrate the data. The SHS scores predicted by the multivariate normal regression analysis are presented