Reduced Cardiorespiratory Fitness Mediates Excess All-cause Mortality in Rheumatoid Arthritis

A study found that low cardiorespiratory fitness (CRF) was a mediator of excess all-cause mortality among patients with rheumatoid arthritis (RA) and suggested that patients take part in physical activity (PA) to increase their CRF.

“Because eCRF is modifiable, results from this study are particularly interesting as increasing PA that leads to improved CRF may translate to reduced mortality rates in patients with RA,” the researchers wrote.

The study assessed participants in the second (1995–1997) and third (2006–2008) waves of the longitudinal population-based Trøndelag Health Study in Norway. Patients with RA (n=348) and controls (n=60,938) were evaluated per a mediation analysis to assess whether low estimated CRF (eCRF) mediated excess relative mortality risk in RA. Cox regression modelling was used to assess all-cause mortality.

Mean follow-up was 19.3 years, during which time patients with RA had a higher mortality rate than controls (36.5% vs. 21.2%; P<0.001). Controls were more likely than patients with RA to have eCRF above the median for their age and sex (51% vs. 26%; P<0.001). RA status and eCRF, adjusted for hypertension, body mass index, smoking, cholesterol, diabetes, and creatine, were included in the final Cox model. A correlation was observed between eCRF below the median for sex and age category and increased mortality (P<0.001). Patients with RA had a total excess relative mortality risk of 28% (95% confidence interval, 2-55%; P=0.035), of which 5% was due to the RA itself, while direct and indirect contributions of low eCRF made up the remaining 23%.

The study was published in RMD Open.

“In addition to optimal medical treatment, focus on improvement and follow-up of CRF should be an integral part of standard treatment of RA already from the time of diagnosis,” the researchers recommended. They also noted, “The present finding that low eCRF clearly acts as a mediator of excess mortality in RA contributes to the evidence supporting improvement of CRF as an important tool for preventive care also in patients with RA.”