Associations of dietary inflammatory index with respiratory tract infections among US adults and the mediating roles of systemic inflammation markers
TL;DR
It is suggested that pro-inflammatory dietary patterns, as reflected by higher DII scores, are associated with increased RTI risk among US adults, and that this relationship may be partially explained by systemic immune–inflammatory dysregulation, supporting inflammation as a biologically plausible pathway linking diet to infection susceptibility.
Abstract
Respiratory tract infections (RTIs) remain a major public health burden among adults, with substantial interindividual heterogeneity in susceptibility. Chronic low-grade systemic inflammation has been proposed as an important host-related determinant of infection risk, and the dietary inflammatory index (DII) provides an integrative measure of the inflammatory potential of habitual diet. However, evidence linking DII to RTI risk and the underlying immune–inflammatory mechanisms remains limited. We analyzed data from 9 cycles of the National Health and Nutrition Examination Survey, including 43,293 adults aged 18 years and older. Dietary inflammatory potential was assessed using DII scores derived from 24-hour dietary recalls, and RTIs were defined based on self-reported recent respiratory infections. Weighted logistic regression models and restricted cubic spline analyses were used to examine the association between DII and RTI risk, while mediation analyses with bootstrapping were performed to quantify the mediating roles of immune–inflammatory indices. In fully adjusted models, higher DII scores were significantly associated with an increased risk of RTIs. Each 1-unit increase in DII was associated with higher odds of RTIs (odds ratio = 1.05, 95% confidence interval: 1.02–1.08; P = .003), and participants in the highest DII quartile had a 23% higher risk of RTIs compared with those in the lowest quartile. Mediation analyses showed that systemic immune–inflammatory indices partially mediated this association. Among the mediators, the systemic immune-inflammation index accounted for the largest proportion of the total effect (10.58%), followed by the platelet-to-lymphocyte ratio (4.22%) and the neutrophil-to-lymphocyte ratio (2.99%). These findings suggest that pro-inflammatory dietary patterns, as reflected by higher DII scores, are associated with increased RTI risk among US adults, and that this relationship may be partially explained by systemic immune–inflammatory dysregulation, supporting inflammation as a biologically plausible pathway linking diet to infection susceptibility.