Berntsen KS; Edvardsen E; Hansen BH; Flato B; Sjaastad I; Sanner H.

Rheumatology. 58(3):492-501, 2019 03 01.

OBJECTIVES: To compare cardiorespiratory fitness (CRF) expressed as
maximal oxygen uptake (VO2max) between patients with long-term JDM and
controls and between patients with active and inactive disease, as well as
to explore exercise limiting factors and associations between CRF and
disease variables.

METHODS: JDM patients (n = 45) and age- and gender-matched controls (n =
45) performed a cardiopulmonary exercise test (CPET) on a treadmill until
exhaustion. Physical activity was measured by accelerometers. Disease
activity, damage and muscle strength/function were assessed by validated
tools. Clinically inactive disease was defined according to PRINTO
criteria.

RESULTS: The mean disease duration was 20.8 (s.d. 11.9) years and 29/45
(64%) patients had inactive disease. A low VO2max was found in 27% of
patients vs 4% of controls (P = 0.006). The mean VO2max and maximal
ventilation (VEmax) were lower in patients with active and inactive
disease compared with controls. Patients with active disease also had
lower maximal voluntary ventilation (MVV) compared with controls and lower
VEmax and MVV compared with those with inactive disease. Patients with
inactive disease had lower physical activity levels compared with
controls. VO2max correlated negatively with disease damage in patients
with inactive disease and positively with muscle strength/function in
patients with active disease.

CONCLUSION: CRF was lower in JDM patients, both with active and inactive
disease, compared with controls after a mean 20 years disease duration.
Cardiopulmonary exercise test results suggested different limiting factors
contributing to the reduced CRF according to disease activity, including
deconditioning in inactive disease and reduced ventilatory capacity in
active disease. Further research is needed to verify this.