Improved Cardiorespiratory Fitness May Lower Risk for Premature Mortality in RA

Low estimated cardiorespiratory fitness (CRF) has been shown to be an important mediator of the increased all-cause mortality rate reported among patients with rheumatoid arthritis (RA). Data derived from the second wave (HUNT2) and third wave (HUNT3) of the longitudinal, population-based Trøndelag Health Study — conducted in the northern region of Trøndelag County in Norway — were used to examine all-cause mortality in patients with RA. Results of the analysis were published in the journal RMD Open.

Recognizing that low CRF is independently associated with all-cause mortality in the general population, the researchers sought to explore whether low CRF is linked to and acts as a mediator of excess all-cause mortality in individuals with RA. The current study used Cox regression modeling to analyze all-cause mortality in 348 patients with RA and 60,938 control patients who participated in wave 2 (1995 to 1997) and wave 3 (2006 to 2008) of  the Trøndelag Health Study.

Of the 348 participants with RA, 71.0% were seropositive, 26.7% were seronegative, and 2.3% had an unknown serologic status. Among these 3 groups of patients, RA disease duration of less than 3 years, 4 to 9 years, and 10 years or longer was 27.9%, 49.7%, and 19.8%, respectively. The mean patient follow-up was 19.3 years, during which time 13,069 participants died.

The all-cause mortality rate was significantly higher among patients with RA compared with control group participants (36.5% vs 21.2%, respectively; P <.001). In control group participants and in patients with RA, 51% and 26%, respectively, had baseline estimated CRF above the median for their age and sex (P <.001). Estimated CRF that was below the median for an individual’s sex and age category was associated with increased mortality (P <.001). The total excess relative risk for mortality was 28% (95% CI, 2% to 55%; P =.035) in patients with RA, with RA itself contributing 5% and the direct and indirect contributions of low estimated CRF accounting for 23% of this relative risk.

Low fitness was strongly associated with mortality in both arms. Of the 127 patients with RA who died, 4% of them belonged to the high-fitness category, as opposed to 8.8% of the control group participants (P =.054). The total time at risk was 1,158,878 person-years — that is, 5596 person-years for those with RA and 1,153,281 person-years for control group participants.

The investigators concluded that along with optimal medical care, a focus on the improvement and follow-up of CRF needs to be an essential part of standard treatment for RA beginning at the time of diagnosis.

Reference

Liff MH, Hoff M, Wisloff U, Videm V. Reduced cardiorespiratory fitness is a mediator of excess all-cause mortality in rheumatoid arthritis: the Trøndelag Health Study. RMD Open. 2021;7(1):e001545. doi:10.1136/rmdopen-2020-001545