Prevalence and prognostic value of elevated urinary albumin excretion in patients with asthma: analysis of NHANES 2001–2018

Abstract

Background: Elevated urinary albumin excretion, quantified as the urinary albumin-to-creatinine ratio (UACR), is a marker of endothelial injury and chronic kidney disease. This study investigates the prevalence and prognostic significance of elevated UACR in asthma patients. Methods: Using data from the National Health and Nutrition Examination Survey (NHANES 2001–2018), 6,930 adults with asthma were analyzed. Participants were stratified by UACR categories: < 30 mg/g (Group 1), 30–300 mg/g (Group 2), and ≥ 300 mg/g (Group 3). Furthermore, for Group1, we further divided it into tertiles. Kaplan–Meier curves, Cox proportional hazards models, restricted cubic splines, and subgroup analyses were employed to assess associations between UACR and mortality. Results: Among 6,930 adults with asthma, 809 all-cause and 195 cardiovascular deaths occurred. Elevated UACR was prevalent in 12.6% (Group 2: 10.5%, Group 3: 2.1%). Compared to Group 1, Group 3 had a higher risk of all-cause mortality (HR: 2.60, 95% CI:1.44–4.71) and cardiovascular mortality (HR: 2.50, 95% CI:1.13–5.55) after full adjustment. Even within the normal range (UACR < 30 mg/g), the highest tertile (Tertile 3) exhibited increased all-cause mortality (HR: 1.69, 95% CI:1.10–2.59). Restricted cubic splines revealed a linear dose–response relationship between UACR and mortality (P for nonlinearity > 0.05). Subgroup analyses confirmed consistency across age, sex, BMI, and comorbidity strata. Conclusions: Elevated UACR is independently associated with higher all-cause mortality in adults with asthma, even at levels below the traditional threshold for albuminuria. These findings underscore UACR as a prognostic biomarker for risk stratification in asthma management.