Arthritis & Rheumatism, Volume 63,
November 2011 Abstract Supplement
Abstracts of the American College of
Rheumatology/Association of Rheumatology Health Professionals
Annual Scientific Meeting
Chicago, Illinois November 4-9, 2011.
Direct and Indirect Effects of Disease Activity on Functional disability in Rheumatoid Arthritis Patients Over Time and the Effect of Increasing Intensive Treatments: Results From Early Utrecht Rheumatoid Arthritis Cohort Study Group.
Nair, Sandhya C., Welsing, P.M.J., Lafeber, F.P.J.G., Bijlsma, J.W.J.
Disease activity influences functional disability in Rheumatiod Arthritis (RA). This influence theoretically constitutes a direct effect (due to current disease activity) and an indirect effect through the effect on joint damage of disease activity over time. It has been found that the direct relation between disease activity and functional disability becomes weaker with higher disease duration, but it has been questioned whether this still is the case with current intensive treatment (1,2). The indirect effect of disease activity on functional disability has not been studied extensively. It is important to understand the relations between these important outcomes and the effect of treatment strategy for the interpretation of disease activity in current tight control treatment strategies. Also with simulation of the progression of the disease in modeling studies as often performed within increasingly performed health-economic studies these relations should be taken into account. The objective of this study was to explore the relation of disease activity with functional disability over time considering indirect and direct associations and also the influence of treatment strategy on these relations.
Data from consecutive randomized clinical trials and their extension phases performed within the Early Utrecht Rheumatoid Arthritis Cohort study group studying increasing intensive treatment strategies were used. Functional capacity was measured using the HAQ and disease activity with the Disease Activity Score 28 (DAS28) every 12 months. Linear mixed models were used to model the longitudinal relation of DAS28 (current and lagged DAS28) and other variables on functional disability of patients over time. To investigate if the influence of variables changed over time interaction terms were tested in the model. Effect modification by treatment strategy was also studied in the model and in subgroup analyses.
Current DAS28 was as expected positively longitudinally associated with HAQ. Lagged DAS28 was independently associated with HAQ. The longitudinal relation of DAS28 with HAQ decreased over disease duration. Remarkably the longitudinal relation of lagged DAS28 with HAQ increased over disease duration. Both were independent of treatment strategy. Although similar relationships between disease activity and functional disability was observed, HAQ progression was lowest in the high intensity treatment group as compared to low intensity treatment group (b=-0.12, p=0.002).
More intensive combination treatment strategies improve the long-term progression of functional disability. Although the longitudinal relation of disease activity with functional disability decreases the influence of lagged disease activity with functional disability increases with disease duration. This further underpins the importance of disease activity as a treatment target for RA early as well as later in the disease course. These results should be confirmed and be taken into account in studies modeling the progression of RA.
To cite this abstract, please use the following information:
Nair, Sandhya C., Welsing, P.M.J., Lafeber, F.P.J.G., Bijlsma, J.W.J.; Direct and Indirect Effects of Disease Activity on Functional disability in Rheumatoid Arthritis Patients Over Time and the Effect of Increasing Intensive Treatments: Results From Early Utrecht Rheumatoid Arthritis Cohort Study Group. [abstract]. Arthritis Rheum 2011;63 Suppl 10 :127