Study on the correlation between serum lead levels and allergic rhinitis in adults and IgE levels

While lead exposure is hypothesized to promote Th2-type allergic responses, large-scale epidemiological data on its link to adult allergic rhinitis (AR) are scarce. This study aimed to explore the association between serum lead levels and AR risk and immunoglobulin E (IgE) levels in the general adult population of the United States. Using data from the 2005-2006 National Health and Nutrition Examination Survey, a cross-sectional study included 2876 participants aged ≥ 20 years, 682 AR patients and 2194 controls. AR was defined as having a positive serum-specific IgE (≥0.35 kU/L) and reporting pollen-related or non-cold-related nasal symptoms in the past 12 months. Serum lead levels was measured using inductively coupled plasma mass spectrometry, and the natural logarithm of serum lead levels (Ln Pb) was adopted. Multivariable logistic regression, linear regression, and Cox regression models were employed to assess the associations after stepwise adjustment for demographic characteristics, lifestyle factors, and laboratory indicators, along with subgroup analyses and restricted cubic spline (RCS) tests for dose-response relationships. Blood lead levels were significantly negatively associated with the risk of AR. Quartile analysis indicated that the highest exposure group (Q4) had a 53% lower risk of AR compared to the lowest group (Q1) (adjusted odds ratio [aOR] = 0.467, 95% confidence interval [CI]: 0.269 to 0.811, P for trend = .014). RCS analysis suggested a linear trend in this association (P-non-linear = .954). Additionally, Ln Pb was positively associated with serum total IgE levels (β = 1.179, 95% CI: 1.005 to 1.383, P = .045), indicating that lead exposure may promote Th2-type immune responses. Higher blood lead levels were also significantly associated with an increased risk of all-cause mortality (HR = 2.535, 95% CI: 1.509 to 4.261, P < .001). Subgroup analyses showed that the negative association between lead and AR was consistent across most populations, but was most pronounced in nondrinkers (HR = 0.53, P = .003), with borderline interaction effects related to smoking status (P for interaction = 0.039). The dissociation between reduced AR risk and elevated IgE levels suggests a complex immunomodulatory effect of lead. Furthermore, lead exposure was confirmed as a significant risk factor for all-cause mortality, underscoring its broader systemic toxicity.