Association between prognostic nutritional index and asthma in US children and adolescents: a cross-sectional study

To evaluate the independent association between prognostic nutritional index (PNI) and asthma risk in children and adolescents and to identify potential threshold effects. To evaluate the independent association between PNI and asthma risk in children and adolescents and to identify potential threshold effects. This cross-sectional study analyzed data from 11,196 participants aged <20 years from NHANES (2003–2020). The diagnosis of asthma was determined based on questionnaire data. PNI was calculated as 10 × albumin (g/dL) + 0.005 × lymphocyte count (10³ cells/μL) and analyzed as both a continuous and tertile variable. Weighted multivariate logistic regression models assessed associations between PNI and asthma. Restricted cubic spline and two-stage regression models examined nonlinear relationships and threshold effects. Subgroup analyses evaluated association stability across populations. Among 11,196 participants, 1,274 (11.5%) reported physician-diagnosed asthma. PNI was inversely associated with asthma risk (OR = 0.963, 95% CI: 0.933–0.995; P = 0.0235). Participants in the highest PNI tertile (T3: 45.014–56.010) had a 34% lower asthma risk than those in the lowest tertile (OR = 0.659, 95% CI: 0.486–0.895; P = 0.0081). Nonlinear analysis revealed an inverse L-shaped relationship (P < 0.001), with a threshold at PNI = 43.40: above this level, higher PNI was protective (OR = 0.93, 95% CI: 0.87–0.98; P = 0.01). Subgroup analyses found no significant interactions (all P > 0.05). Higher PNI levels are associated with reduced asthma risk in children and adolescents, with a protective effect at PNI ≥43.40. However, further research is required to elucidate the underlying mechanisms of this association and explore the potential of PNI as a predictive biomarker for asthma in children and adolescents.