Development of reduced kidney function in rheumatoid arthritis.

BACKGROUND

Rheumatoid arthritis (RA) is associated with a variety of kidney disorders. However, it is unclear whether the development of reduced kidney function is higher in patients with RA compared to the general population.

STUDY

DESIGN

Retrospective review.

SETTING &

PARTICIPANTS

Incident adult-onset RA cases (813) and a comparison cohort of non-RA individuals (813) in Olmsted County, MN, in 1980-2007.

PREDICTOR: Baseline demographic and clinical variables.

OUTCOMES: Reduced kidney function: (1) estimated glomerular filtration rate (eGFR)<60mL/min/1.73m(2) and (2) eGFR<45mL/min/1.73m(2) on 2 consecutive occasions at least 90 days apart; cardiovascular disease (CVD); and death.

MEASUREMENTS: The cumulative incidence of reduced kidney function was estimated adjusting for the competing risk of death.

RESULTS

Of 813 patients with RA and 813 non-RA individuals, mean age was 56±16 (SD) years, 68% were women, and 9% had reduced kidney function at baseline. The 20-year cumulative incidence of reduced kidney function was higher in patients with RA compared with non-RA participants for eGFR < 60mL/min/1.73m(2) (25% vs 20%; P=0.03), but not eGFR<45mL/min/1.73m(2) (9% vs 10%; P=0.8). The presence of CVD at baseline (HR, 1.77; 95% CI, 1.14-2.73; P=0.01) and elevated erythrocyte sedimentation rate in patients with RA (HR per 10-mm/h increase, 1.08; 95% CI, 1.00-1.16; P=0.04) was associated with increased risk of eGFR<60mL/min/1.73m(2). eGFR<60mL/min/1.73m(2) was not associated with increased risk of CVD development in patients with RA (HR, 0.99; 95% CI, 0.63-1.57; P=0.9), however, a greater reduction in GFR (eGFR<45mL/min/1.73m(2)) was associated with increased risk of CVD (HR, 1.93; CI, 1.04-3.58; P=0.04).

LIMITATIONS: Reduced kidney function was defined by estimating equations for kidney function. We are limited to deriving associations from our findings.

CONCLUSIONS

Patients with RA were more likely to develop reduced kidney function over time. CVD and associated factors appear to play a role. The presence of RA in individuals with reduced kidney function may lead to an increase in morbidity from CVD development, for which awareness may provide a means for optimizing care.