Inflammation and metabolic processes are closely interrelated and collectively influence aging. The remnant cholesterol inflammatory index (RCII) is a composite biomarker that integrates both inflammatory and metabolic dimensions. Although studies have separately reported the associations of inflammation or metabolic disorders with biological aging, the relationship between the combined inflammatory-metabolic burden and biological aging remains underexplored.

To investigate the association between RCII and biological age acceleration (BAA).

This study used cross-sectional data from participants with RCII and biological age data in the China Health and Retirement Longitudinal Study (CHARLS) from waves 2011 and 2015. A total of 11 140 middle-aged and older adults were selected as study subjects. Based on the quartiles of lnRCII levels, participants were divided into four groups: Q1 group (lnRCII≤0.97, n=2 785), Q2 group (0.97<lnRCII≤2.36, n=2 786), Q3 group (2.36<lnRCII≤6.19, n=2 784), and Q4 group (lnRCII>6.19, n=2 785). Biological age was calculated using the Klemera-Doubal method, and BAA was defined as the difference between biological age and chronological age. Multiple linear regression models and restricted cubic splines were performed to explore the association between RCII and BAA. Additionally, subgroup and sensitivity analyses were performed to assess the consistency and robustness of this association across different populations.

A total of 11 140 study subjects were included, with a median age of 57 (50, 65) years and a mean biological age of 57.8±9.8 years, including 4 970 males (44.61%) and 6 170 females (55.39%). Statistically significant differences were observed among the four groups in terms of age, BMI, education level, residence, hypertension, diabetes, cardiovascular disease, lipid-lowering treatment, glucose-lowering treatment, remnant cholesterol, RCII, lnRCII, biological age, and BAA (P<0.05). The results of multiple linear regression analysis showed that after adjusting for all covariates, there was a significant positive association between lnRCII and BAA. For each one-unit increase in lnRCII, BAA increased by 0.28 years (β=0.28, 95%CI=0.25-0.32, P<0.001); moreover, for each one-standard deviation (SD) increase in lnRCII, BAA increased by 0.41 years (β=0.41, 95%CI=0.36-0.45, P<0.001); BAA in the Q4 group was 1.10 years higher than that in the Q1 group (β=1.10, 95%CI=0.97-1.23, P<0.001). The restricted cubic spline analysis showed a positive nonlinear dose-response relationship between lnRCII and BAA (P_nonlinearity<0.001). Subgroup analysis results showed a positive association between lnRCII and BAA in all subgroups (P<0.05); there were interactions between lnRCII and BAA in the subgroups of sex, age, BMI, residence, and diabetes, and the associations were more pronounced in females, individuals aged<60 years, obese individuals, urban residents, and those with diabetes (P_interaction<0.05).

Among middle-aged and older Chinese adults, RCII shows a significant positive nonlinear association with BAA, and this association is particularly prominent in females, individuals aged<60 years, obese individuals, urban residents, and those with diabetes. RCII is expected to become a key tool for community-based screening of high-risk populations for "premature aging" and guiding targeted interventions to promote healthy aging.

炎症与代谢过程密切相关且共同影响着衰老。残余胆固醇炎症指数（RCII）是一种整合了炎症与代谢两个维度的复合生物标志物。目前虽有研究分别报道了炎症或代谢紊乱与生物学衰老的相关性，但炎症-代谢复合负担与生物学衰老的关联仍缺乏探讨。

探讨RCII与生物学年龄加速（BAA）之间的关联。

本研究使用了2011年和2015年中国健康与养老追踪调查（CHARLS）中具有RCII和生物学年龄数据参与者的横断面数据，从中选取11 140例中老年人为研究对象，根据lnRCII水平四分位数将研究对象分为4组：Q1组（lnRCII≤0.97，2 785例）、Q2组（0.97<lnRCII≤2.36，2 786例）、Q3组（2.36<lnRCII≤6.19，2 784例）、Q4组（lnRCII>6.19，2 785例）。其中生物学年龄通过Klemera-Doubal方法计算得出，BAA被定义为生物学年龄与实际年龄的差值。本研究采用多元线性回归模型和限制性立方样条分析来探讨RCII与BAA之间的关联。此外，通过亚组分析和敏感性分析检验该关联在不同人群中的一致性和稳定性。

共纳入11 140例研究对象，中位年龄为57（50，65）岁，平均生物学年龄为（57.8±9.8）岁，其中男4 970例（44.61%）、女6 170例（55.39%）。4组研究对象年龄、BMI、受教育程度、居住地、高血压、糖尿病、心血管疾病、降脂治疗、降糖治疗、残余胆固醇、RCII、lnRCII、生物学年龄、BAA比较，差异有统计学意义（P<0.05）。多元线性回归分析结果显示，调整所有协变量后，lnRCII与BAA呈正相关，lnRCII每增加1个单位，BAA就增加0.28年（β=0.28，95%CI=0.25~0.32，P<0.001）；而且，lnRCII每增加1个标准差（SD），BAA就增加0.41年（β=0.41，95%CI=0.36~0.45，P<0.001）；Q4组研究对象的BAA比Q1组增加1.10年（β=1.10，95%CI=0.97~1.23，P<0.001）。限制性立方样条模型分析结果显示，lnRCII与BAA之间的剂量反应关系呈正相关的非线性关系（P_非线性<0.001）。亚组分析结果显示，lnRCII与BAA在各亚组中均呈正相关（P<0.05）；lnRCII与BAA在性别、年龄、BMI、居住地、糖尿病亚组存在交互作用，且在女性、<60岁、肥胖、城镇居民、糖尿病个体中更显著（P_交互<0.05）。

在我国中老年人群中，RCII与BAA存在显著的正向非线性关联，且该关联在女性、<60岁、肥胖、城镇居民、糖尿病个体中尤为突出。RCII有望成为社区筛查"早衰"高危人群并指导靶向干预以促进健康衰老的关键工具。