This study aimed to determine the prevalence of CKD in a large Chinese RA cohort, characterize the clinical features of RA patients with CKD, and identify independent risk factors, with emphasis on effect modifications by age and sex.

We conducted a retrospective study of RA patients (aged≥18 years, meeting the 2010 ACR/EULAR criteria) attending a tertiary center between January 2015 and December 2024. Patients with other autoimmune diseases, active malignancy, or acute kidney injury were excluded. Data on demographics, disease activity (DAS28/CDAI), comorbidities, and medications were collected. CKD was defined as an estimated glomerular filtration rate (eGFR) <60 ml/min/1.73m², calculated using the CKD-EPI 2021 creatinine equation and sustained for ≥3 months. Univariate and multivariate logistic regression analyses were performed to identify factors associated with CKD. Subgroup analyses and interaction tests assessed effect modifications by age (<60 vs. ≥60 years) and sex.

Among 1683 eligible RA patients (82.8% female, mean age 52.2±12.5 years, median disease duration 3.9 years), the mean eGFR was 92.1±20.3 ml/min/1.73m². A total of 121 patients (7.2%) met the criteria for CKD. CKD prevalence increased markedly with age: 1.7% (40–49 years), 4.4% (50–59 years), 13.2% (60–69 years), 32.4% (70–79 years), and 69.2% (≥80 years) (P<0.001，Figure 1A). Compared with non-CKD patients, those with CKD were significantly older (65.9 vs. 51.1 years, P<0.001), had longer disease duration (5.3 vs. 3.9 years, P=0.002), and exhibited higher disease activity (median CDAI 20.0 vs. 14.0, P=0.003).

Comorbidities were more frequent in the CKD group: hypertension (62.8% vs. 24.3%, P<0.001, Figure 1B&C), type 2 diabetes (26.4% vs. 10.9%, P<0.001, Figure 1B&D), and hyperlipidemia (44.6% vs. 28.6%, P<0.001, Figure 1B&E). CKD prevalence was 4.5 times higher in RA patients with hypertension than in those without (16.7% vs. 3.7%, P<0.001).

Multivariate logistic regression confirmed older age (OR=1.127, 95% CI: 1.101–1.154, P<0.001) and hypertension (OR=2.618, 95% CI: 1.726–3.971, P<0.001) as independent risk factors for CKD (Table 1). Subgroup analysis revealed significant interaction effects (P<0.001). Hypertension was associated with a substantially higher OR for CKD in younger patients (<60 years) compared with older patients (≥60 years), and within the younger group, the association was strongest in males (OR=12.750, 95% CI: 1.284–126.625) compared with females (OR=3.801, 95% CI: 1.729–8.360).

In this large Chinese RA cohort, 7.2% of patients had CKD, with prevalence escalating after age 60. Age and hypertension are key independent risk factors. Notably, the detrimental effect of hypertension on CKD risk is significantly modified by age and sex, being most pronounced in young male RA patients. These findings underscore the need for vigilant renal function monitoring and aggressive, tailored blood pressure management in RA patients, with particular attention to young males, as a potential strategy to mitigate CKD development and progression.