Background/Purpose: To study the effect of the metabolic syndrome (MetS) on renal function decline in four rheumatic diseases.

Methods: Consecutive patients who fulfilled the ACR/SLICC criteria for systemic lupus erythematosus (SLE), EULAR/ACR criteria for rheumatoid arthritis (RA), ASAS criteria for spondyloarthritis (SpA) and the CASPAR criteria for psoriatic arthritis (PSA) were recruited in 2009/2010.  At entry, patients recruited had measurement of body weight, height, waist circumference and blood pressure.  MetS was defined by the updated joint consensus criteria, using the Asian criteria for central obesity, when ≥3 of the following were present: (1) waist ≥90cm in men or ≥80cm in women; (2) blood pressure ≥130/85mmHg or requiring therapy; (3) serum triglyceride level ≥1.7mmol/L; (4) serum HDL-chol ≤1.0mmol/L in men and 1.3mmol/L in women; and (5) fasting glucose ≥5.6mmol/L.  Renal function of the participants was assessed by the 4-variable MDRD formula (eGFR).  Patients were followed longitudinally for eGFR change.  Change in eGFR was compared between those with and without the MetS at baseline.  Regression analysis was performed for the effect of MetS on eGFR decline adjusted for other confounding factors.

Results: 1497 patients were studied (693 RA, 577 SLE, 121 SpA and 106 PSA).  The age at entry was highest in RA (53.4±12.0 years) and lowest in SpA (39.0±11.9 years).  Disease duration was longest in SLE (9.3±7.2 years) and shortest in PSA (3.6±3.2 years).  MetS was present in 137 RA (20%), 85 SLE (15%), 13 SpA (11%) and 39 PSA (37%) patients.  Patients were followed for 91.1±12.1 months.  The mean decline of eGFR (ml/min/1.73m2) at last observation from baseline was 5.00±13.5 in RA, 4.16±11.6 in SpA, 3.95±12.3 in PSA and 8.93±16.4 in SLE (p=0.03; one-way ANOVA).  The proportion of patients with eGFR decline by ≥10% was also greatest in SLE (41%) compared with RA (29%), SpA (24%) and PSA (25%) patients (p< 0.001).  Among patients with SLE, a significantly more profound drop in eGFR over 8 years was observed in patients with the MetS at baseline (-17.8±26%) than those without (-7.6±18%; p=0.002).  The difference in last eGFR between patients with and without the MetS was significant after adjustment for baseline eGFR, age and sex (65.5±32.2 vs 88.4±24.4 ml/min/1.73m2; p< 0.001).  In a linear regression model, eGFR at last follow-up was significantly associated with the baseline eGFR (slope 0.72 SE 0.03; Beta 0.77; p< 0.001), renal involvement (slope -4.36 SE 1.30; Beta -0.08; p=0.001) and the MetS (slope -6.88 SE 1.86; Beta -0.09; p< 0.001).  In patients with RA/SpA/PSA, eGFR also showed a greater trend of decline over time in those with MetS than without, but the difference did not reach statistical significance.

Conclusion: Among patients with common rheumatic diseases, SLE showed the greatest decline in renal function over time.  The presence of MetS in SLE significantly accelerated renal function decline over time independent of the presence of renal disease.  The MetS also unfavorably affected eGFR in patients with inflammatory arthritis.  A more detailed analysis on the causes of eGFR decline in individual diseases and a longer period of follow-up of the renal function is needed.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/effect-of-the-metabolic-syndrome-on-renal-function-decline-in-four-rheumatic-diseases-an-8-year-longitudinal-analysis/