Weight-adjusted waist index (WWI), a novel indicator of central obesity, has been suggested to be potentially associated with depression. Nevertheless, most available evidence comes from cross-sectional studies, and the direction, strength, and independence of this relationship across different populations remain uncertain. Specifically, there is a lack of large-scale longitudinal studies investigating this association in the Chinese middle-aged and elderly population.

To analyze the longitudinal association between the WWI and the risk of depression in middle-aged and older Chinese adults, providing a scientific basis for the prevention and intervention of depression in this population.

A longitudinal study design was adopted based on data from the China Health and Retirement Longitudinal Study (CHARLS) from 2011 to 2018. Depressive symptoms and anthropometric indicators were collected, and WWI was calculated as waist circumference divided by the square root of body weight . Logistic regression models were employed to examine the association between WWI levels and depression. Restricted cubic spline (RCS) curves were used to assess the dose-response relationship between WWI levels and depression risk. Subgroup analyses were conducted based on age, sex, obesity, smoking, and alcohol consumption to evaluate population heterogeneity. Finally, the predictive performance of WWI for depression was assessed using receiver operating characteristic (ROC) curves.

A total of 7 464 middle-aged and older adults were enrolled, with a median WWI of 11.06 (10.52, 11.62). Participants were stratified into four quartile groups based on WWI; the median WWI values for Q1 to Q4 were 10.14 (9.81, 10.35), 10.80 (10.66, 10.93), 11.31 (11.18, 11.46) and 12.04 (11.80, 12.45), respectively. During follow-up, the cumulative incidence of depressive symptoms was 47.11% (879/1 866), 47.21% (881/1 866), 49.25% (919/1 866) and 53.70% (1 002/1 866) across Q1-Q4. The incidence rose progressively with increasing WWI (P<0.05). Logistic regression indicated that, compared with those in the Q1 group, participants in the Q4 group had a 23% higher risk of depression (OR=1.23, 95%CI=1.05-1.44). RCS analysis revealed that the risk of depression increased with higher WWI levels, with each 1-unit increase in WWI associated with a 2% higher risk of depression (OR=1.02, 95%CI=1.00-1.04). Subgroup analysis showed that the association between WWI and depression risk was more pronounced in individuals aged <65 years (interaction P<0.05). ROC analysis indicated that WWI had better predictive value for depression than body fat index (AUC: 0.588 vs. 0.531; P<0.05), with an optimal cutoff value of 11.36 for increased depression risk.

Elevated WWI levels are associated with an increased risk of depression in middle-aged and older Chinese adults, particularly in those under 65 years of age. WWI may serve as a potential indicator for depression prevention and intervention strategies

体质量调整腰围指数（WWI）作为反映中心性肥胖的新指标，被认为与抑郁存在潜在关联，但现有证据多来自横断面研究，且二者关系在不同人群中的作用方向、强度及独立性尚不明确，尤其是在中国中老年人群中，缺乏大样本纵向研究证据。

探讨中国中老年人群WWI与抑郁发生风险的关联，为中老年人抑郁防治提供科学依据。

采用纵向研究设计，基于中国健康与养老追踪调查（CHARLS）2011—2018年的4次调查数据开展分析，收集中老年人的抑郁症状及人体测量指标等，并计算WWI（WWI=腰围/）。采用Logistic回归模型分析WWI与抑郁发生的关联，基于限制性立方样条曲线（RCS）评估WWI与抑郁发生的剂量反应关系；设置年龄、性别、BMI、目前吸烟和饮酒情况的亚组，评估WWI水平与抑郁发生的人群异质性；通过受试者工作特征（ROC）曲线评估WWI对抑郁发生的预测效能。

本研究共纳入7 464名中老年人，中位WWI为11.06（10.52，11.62）。根据四分位数分组，Q1组~Q4组的中位WWI分别为10.14（9.81，10.35）、10.8（10.66，10.93）、11.31（11.18，11.46）、12.04（11.8，12.45）。随访期内，Q1组~Q4组的抑郁发生率分别为47.11%（879/1 866）、47.21%（881/1 866）、49.25%（919/1 866）、53.70%（1 002/1 866），抑郁发生率随WWI升高而增加（P<0.05）。Logistic回归分析结果显示，当调整其他协变量后，相比于Q1组，Q4组的抑郁发生风险增加23%（OR=1.23，95%CI=1.05~1.44）。RCS结果显示，抑郁发生风险随WWI升高而增加，WWI水平每增加1个单位，抑郁发生风险增加2%（OR=1.02，95%CI=1.00~1.04）。亚组分析结果显示，WWI与抑郁发生风险的关联在<65岁人群更为明显（P_交互<0.05）。ROC曲线结果显示，WWI对抑郁发生的预测价值高于BMI（ROC曲线下面积：0.588比0.531，P<0.05），WWI预测抑郁发生的临界值为11.36。

中老年人群WWI水平升高与抑郁发生风险相关，尤其是在年龄<65岁人群中，WWI可以作为抑郁预防和干预的潜在指标。