Aerobic capacity in rheumatoid arthritis : aspects of associations with cardiovascular risk factors and disease activity

Sammanfattning: Rheumatoid arthritis (RA) is a systemic and inflammatory disease that has been associated with an increased morbidity and mortality in cardiovascular disease (CVD). Low aerobic capacity is one of the strongest independent risk factors for CVD and all-cause mortality in the general population. In patients with longstanding RA, low aerobic capacity has been related with a worse cardiovascular profile and an increased risk of CVD mortality. As a consequence of this, low aerobic capacity might provide an additional risk factor for CVD in patients with RA. The aim of this thesis was to describe the associations between aerobic capacity and risk factors for CVD as well as disease activity in patients with early RA, and also the effects of intensive exercise therapy on traditional risk factors for CVD and disease activity in patients with longstanding RA.Paper I, a cross-sectional study including 67 patients with early RA, mean (SD) age 53.1 (14.4), assessments of aerobic capacity, CVD risk factors, disease activity and functional ability were taken. Data were analysed for the associations between aerobic capacity and CVD risk factors and disease activity. In paper II, an intervention study, including 13 patients with RA, median age (Q1-Q3) 57 (44-64) years, aerobic capacity, pulse wave analysis (PWA), CVD risk factors, and disease activity were analysed for changes after 10 weeks of intensive exercise therapy. Additional follow-up was made after 25 weeks.In paper I, the mean (SD) aerobic capacity was 31.6 (8.7) ml O2/kg/min. CVD risk factors and disease activity were all in favour of patients with higher aerobic capacity. In a multiple regression model, adjusted for age and sex, aerobic capacity was significantly associated with percent body fat (β=-0.502, 95%CI=-0.671;-0.333) and triglycerides (β=-2.365, 95%CI=-4.252;-0.479). In paper II, intensive exercise over ten weeks was shown to be a feasible method to significantly improve aerobic capacity (p=≤0.05), systolic blood pressure (p=≤0.01) and the number of tender joints (p=≤0.05). No detrimental effect on disease activity was recorded.This thesis adds further knowledge of aerobic capacity and its associations with CVD risk factors and disease activity in patients with RA. Also, intensive exercise therapy was a feasible intervention to improve CVD risk factors. To include assessment of aerobic capacity in regular clinical practice may improve patient management as well as patient outcome in patients with RA.