Background: Kidney biomarkers vary by age, ethnicity, sex, and lifestyle, yet population-level patterns across these axes remain incompletely characterized. Objective: To examine the potential impact of age, ethnicity, sex, and smoking status on kidney function abnormalities and their combined effects. Method: NHANES 1999–2020 data were analyzed incorporating survey weights, strata, and primary sampling units. Participants were aged ≥12 years with valid kidney laboratory measurements; smoking status was self-reported among adults. Biomarkers included serum creatinine (Scr), blood urea nitrogen (BUN), uric acid, urine albumin, and urine albumin-to-creatinine ratio (uACR). The estimated glomerular filtration rate (eGFR) was derived from Scr using the MDRD (2007) and CKD-EPI (2009) equations with IDMS-standardized creatinine. Weighted descriptive statistics were produced, and survey-weighted multivariable logistic regression models were fitted using prespecified covariates. Two- and three-way interaction terms were evaluated with Wald tests (two-sided α = 0.05). Results: In 72 287 participants, males displayed a less favorable kidney profile than females, with higher Scr (0.96 vs 0.74 mg/dl), uric acid (5.95 vs 4.72 mg/dl), and BUN (13.96 vs 12.28 mg/dl; all P < 0.0001), but lower eGFR (102.7 vs 104.5 ml/min/1.73 m 2 ; P < 0.0001). Ethnic disparities were pronounced: non-Hispanic blacks exhibited the highest Scr, non-Hispanic whites the highest BUN (14.75 vs 12.75 mg/dl in Black males) and lowest eGFR, whereas Mexican Americans had the highest eGFR (adult females ≈ 109 vs 84–91 ml/min/1.73 m 2 across equations). Smoking was associated with an adverse renal profile in non-Hispanic blacks and Mexican Americans, including eGFR reductions of −6.76 and −5.08 ml/min/1.73 m 2 (both P < 0.001). Multivariable logistic regression analyses confirmed age as the dominant determinant of abnormal kidney markers. Male sex markedly increased the risk of abnormal Scr and uric acid but was protective for eGFR and uACR. Black race was associated with higher odds of Scr, uric acid, and albuminuria, whereas Mexican Americans had lower risks of abnormal Scr, uric acid, and eGFR but greater risks of albuminuria/uACR. Lower socioeconomic status, hypertension, and diabetes consistently predicted albuminuria and reduced eGFR, underscoring the role of both social disadvantage and cardiometabolic comorbidity in shaping renal risk. Conclusions: Kidney function varies according to ethnicity, sex, age, and smoking status. Black participants show a high-filtration–high-leak pattern (higher eGFR with elevated albuminuria/uACR); White participants exhibit lower eGFR with higher BUN; Mexican Americans display high-filtration–low-metabolic features (higher eGFR with lower creatinine/uric acid).
Zhao et al. (Wed,) studied this question.