Effect of Ageing on Interpretation of Disease Activity Measures and on Cognition, Physical Activity and Performance in Patients With Rheumatic Disorders

The primary objective of the STAR study is to investigate how measures of disease activity and measures for cognition, physical activity and performance behave in ageing population controls and patients with rheumatoid arthritis (RA). If an differential effect of age on outcome over time is apparent, the presence of an inclination point will be assessed. The secondary objective is to investigate additional factors (e.g. lifestyle factors) that might explain any differences between ageing controls and RA patients. The STAR study is an observational cross-sectional matched case-control study including 420 RA patients and 420 population controls between 55-85 years of age, stratified by five year intervals. All participants will complete generic and RA-specific questionnaires. A subset of 180 participants will be visiting the research center for physical examination and performance tests. Expected outcomes include practical age-specific reference curves that will be constructed for a selection of outcomes (e.g. DAS28). It is expected that as RA is characterized by tender and painful joints, e.g. the number of tender joints has a higher starting point in RA patients than in the general population. This will most likely increase in both groups with age, although the general population may catch up at an older age. Measures of cognitive status may show a steeper decline with age in RA patients compared to the general population. Measures of physical activity and performance will presumably have a worse starting point in RA patients than in the general population, and might show a steep decline with age. The general population might however catch up with the patients with RA. Most probably, age will not be the only factor explaining 'worse' outcomes in both RA patients and the general population. Other factors such as lifestyle factors (e.g. smoking, diet, BMI, occupation) and comorbidities will probably play a role.