Patients with ankylosing spondylitis (AS) with reduced cardiorespiratory fitness had a significantly increased risk for cardiovascular disease (CVD), according to findings published in The Journal of Rheumatology. This relationship was independent of conventional CVD risk factors and AS disease activity measures.
Although lower cardiorespiratory fitness is associated with increased CVD in the general population, this association had not been previously analyzed in AS or other inflammatory joint diseases. Investigators hypothesized an independent inverse correlation between cardiorespiratory fitness and CVD risk.
A cross-sectional study examined a cohort of 118 patients with AS (mean age, 48.9 years; 64% men), with disease activity measured by the Ankylosing Spondylitis Disease Activity Score using C-reactive protein (ASDAS-CRP) and the Bath Ankylosing Spondylitis Disease Activity Index. Peak oxygen uptake measured with maximal treadmill walking was used to assess cardiorespiratory fitness, and arterial stiffness, represented by augmentation index (AIx) and pulse wave velocity (PWV), was used to estimate the risk for CVD. CRP was also measured, and backward multivariate linear regression analysis was used to investigate any associations between peak oxygen uptake and arterial stiffness.
Using scatterplots, the researchers detected significant inverse relationships between peak oxygen uptake and both AIx (P <.001) and PWV (P <.001), indicating that poorer cardiorespiratory fitness was linked to increased CVD risk. Multivariate regression revealed significant, independent, inverse associations between peak oxygen uptake and AIx (β = −0.3; 95% CI, −0.6 to −0.1; P =.01) and between peak oxygen uptake and log-transformed PWV (β = −0.005; 95% CI, −0.010 to −0.001, P = .03). No interactions between peak oxygen uptake and CRP or between peak oxygen uptake and the ASDAS-CRP were found.
Study limitations included the inability to discern causation, the possibility of bidirectional effects, the potential underestimation of peak oxygen uptake in patients with physical disabilities, and that biomarker associations should be interpreted cautiously.
“We found that low [peak oxygen uptake] was associated with higher arterial stiffness in patients with AS, indicating that low [cardiorespiratory fitness] is associated with increased CVD risk,” concluded the authors. They noted that regular aerobic exercise can be a method to improve cardiorespiratory fitness and decrease CVD risk, but warned that high disease activity that prevents patients from getting such exercise may first need to be addressed to facilitate this change. Future longitudinal intervention trials were recommended to evaluate the effect of exercise on cardiorespiratory fitness and CVD risk in the AS population.
Berg IJ, Semb AG, Sveaas SH, et al. Associations between cardiorespiratory fitness and arterial stiffness in ankylosing spondylitis: a cross-sectional study. J Rheumatol. 2018;45(7):1-4.