Predictors for health-related quality of life in patients with rheumatoid arthritis: a longitudinal study.

Objectives: Existing observational research on predictors of health-related quality of life (HRQoL) in patients with RA is mostly limited to cross-sectional designs and often focuses on one or a few predictors. This is the first comprehensive analysis of a set of selected predictors in a longitudinal setting. Methods: A total of 361 individuals with RA were included in the study. HRQoL (physical and mental component summary scales of the 12-item Short Form Health Survey) was assessed at baseline, 3- and 12-month follow-ups. In total, 19 predictors were assessed at baseline, grouped into six thematic blocks: demographics (age, sex, education), disease-related factors (duration of disease, pain, illness severity), therapy-related factors (side effects, number of RA medicines, type of prescribed RA medication), psychological variables (beliefs about medicines, social support, depression, anxiety), behaviour (adherence) and lifestyle (obesity). Hierarchical multiple linear regression analysis was employed to test the influence of individual (groups of) predictor variables on HRQoL. Results: Only pain (as a disease-related factor) predicted both physical and mental HRQoL at all follow-ups. For physical HRQoL, age was a significant predictor at both follow-ups, as were anxiety and depression (psychological variables) for mental health HRQoL. For all other included variables, findings were non-significant or inconsistent across measurement points. Conclusion: Even though the selection of possible predictors was based on previous research findings, analysis revealed that the impact may not be as robust as previously thought. More longitudinal research is needed to specify factors that impact HRQoL in RA patients in the long run.