Objective  To investigate the association between the oxidative balance score (OBS) and atherogenic index of plasma (AIP), providing scientific evidence for the early identification and prevention of atherosclerosis (AS).

Methods  A total of 8 851 eligible participants from the surveillance data of cardiovascular diseases and related risk factors in Fujian Province from August 2020 to April 2021 were included. The OBS was calculated using four dietary nutrient factors and six lifestyle-related factors. AIP was used as a surrogate marker of AS risk, and participants were categorized into a low-AIP group (AIP ＜ 0.24) and a high-AIP group (AIP ≥ 0.24). Unconditional logistic regression was used to examine the association between OBS and AIP. Restricted cubic spline (RCS) analysis was conducted to evaluate the dose–response relationship. Subgroup analyses and multiplicative interaction tests were performed to explore the associations in different populations. Mediation analysis was used to assess the potential mediating effects of uric acid (UA), white blood cells (WBC), and neutrophil (NE).

Results  Multivariable logistic regression analysis showed a negative association between OBS and high AIP levels (OR = 0.89, 95%CI: 0.87 to 0.91, P＜0.001). Compared with participants in the lowest quartile (Q1) of OBS, those in the highest quartile (Q4) had 40% lower risk of high AIP (OR = 0.60, 95%CI: 0.49 to 0.72, P＜0.001). Subgroup analyses revealed significant multiplicative interactions between OBS and age (P for interaction = 0.012) as well as dyslipidemia (P for interaction = 0.010). In addition, a non-linear dose–response relationship was observed between OBS and AIP (P for nonlinearity ＜ 0.001). Mediation analysis indicated that UA, WBC, and NE partially mediated the association between OBS and AIP.

Conclusions OBS is inversely associated with AIP, and there are significant multiplicative interactions between OBS and age and dyslipidemia.