Joint association of atherogenic index of plasma (AIP) and body roundness index (BRI) with cardiometabolic multimorbidity in adults in Guangzhou, China

Cardiometabolic multimorbidity (CMM) is one of the most prevalent patterns of multimorbidity worldwide and presents a growing challenge to public health. Metabolic dysregulation and visceral adipose play central roles in the development of CMM. The atherogenic index of plasma (AIP) has been proposed as a comprehensive indicator of lipid metabolic abnormalities, whereas the body roundness index (BRI) is a novel anthropometric measure reflecting central obesity and visceral adipose tissue (VAT). However, evidence regarding the associations of AIP and BRI with CMM remains limited, particularly in southern Chinese populations and young adults. This study examined the separate and joint associations of AIP and BRI with CMM, aiming to provide preliminary scientific evidence to identify individuals more likely to have prevalent CMM. This cross-sectional study included 2505 adults from the 2024 Guangzhou Residents’ Nutrition Survey. Multivariable logistic regression models and segmented logistic regression analyses were employed to examine the association patterns of AIP and BRI with CMM, as well as to assess potential threshold effects. For joint analysis, participants were categorized into four groups by AIP and BRI levels to evaluate the joint association and interaction between these indices and CMM. Among the 2505 participants, 213 (8.50%) were diagnosed with CMM. Compared with the lowest tertile, the highest tertile of AIP (OR = 4.025, 95% CI 2.591–6.455) and BRI (OR = 10.461, 95% CI 5.523–22.496) were associated with a higher likelihood of CMM. AIP was linearly associated with CMM. In contrast, BRI demonstrated a nonlinear association with CMM, with an inflection point at 4.52, below which the odds of CMM increased more rapidly. Joint analyses revealed that participants in the “high AIP+high BRI” group had the strongest association with CMM (OR = 5.081, 95% CI 3.354–7.828). Subgroup analysis revealed that the association between the “high AIP+high BRI” group and CMM was stronger in participants < 60 years. Individuals with elevated levels of AIP and BRI are more likely to have CMM. AIP is linearly associated with CMM, whereas a threshold effect is observed for BRI. The joint assessment of AIP and BRI demonstrates a stronger association with CMM compared to either indicator alone. These findings suggest that the joint assessment of AIP and BRI may be a useful tool for identifying individuals at a higher likelihood of prevalent CMM, particularly in young and middle-aged adults.