Association between dietary inflammatory index and visual impairment among adults in the NHANES 2005-2008

The association between the dietary inflammatory index (DII) and visual impairment remains unclear. This study aimed to investigate the relationship between the DII and non-refractive visual impairment among US populations. A cross-sectional analysis was conducted using data from the National Health and Nutrition Examination Survey (NHANES) 2005-2008, including dietary information and visual impairment assessment. Participants with presenting visual impairment, defined as presenting visual acuity in the better-seeing eye worse than 20/40, were included. Participants whose visual acuity in the better-seeing eye could be corrected to 20/40 or better through automated refraction, were classified as having uncorrected refractive error, while others were considered to have non-refractive visual impairment. Logistic regression models, restricted cubic spline (RCS) analysis, subgroup analyses, and propensity score matching (PSM) were performed to assess the association between DII and the prevalence of non-refractive visual impairment. After adjusting for potential confounding factors, a positive association was observed between DII scores and the prevalence of non-refractive visual impairment (odds ratio [OR] = 1.277, 95% confidence interval [CI] = 1.017-1.603, P < 0.05). RCS analysis demonstrated that there was no nonlinear relationship between them (P for nonlinear > 0.05). Furthermore, sensitivity analysis by PSM indicated the robustness of this positive association. This study revealed a positive correlation between the DII and the prevalence of non-refractive visual impairment among those with presenting visual impairment in the United States. Further prospective studies are warranted to confirm a causal relationship and elucidate the underlying mechanisms involved.