U-Shaped Associations Between Metabolic Indices and Depression in Middle-aged and Older Adults: A Data-Driven Cross-Sectional Study from CHARLS

Main Article Content

Yajie Liang

Keywords

digital economy, labor market structure, skill-biased technological progress

Abstract

Objective: While the relationship between metabolic dysregulation and depression is well-established, its specific nature in the elderly remains obscure, partially due to the limitations of traditional metrics like BMI in distinguishing visceral fat. This study aimed to systematically investigate the associations between novel composite metabolic indices and depressive symptoms in community-dwelling Chinese middle-aged and older adults, with a particular focus on non-linear threshold effects. Methods: This cross-sectional analysis utilized nationally representative data from the China Health and Retirement Longitudinal Study (CHARLS), comprising 10,195 participants aged ≥45 years. Depressive symptoms were assessed using the 10-item Center for Epidemiologic Studies Depression Scale (CES-D-10). Four novel indices were calculated: China Visceral Adiposity Index (CVAI), Lipid Accumulation Product (LAP), Metabolic Score for Insulin Resistance (METS-IR), and Metabolic Score for Visceral Fat (METS-VF). Besides conventional statistics, we employed multivariable logistic regression to decode the independent associations, with a particular focus on identifying non-linear threshold effects. Results: After adjusting for sociodemographic, lifestyle, and clinical confounders, CVAI, LAP, METS-IR, and METS-VF allexhibited significant U-shaped nonlinear associations with depressive symptoms.  Contrary to linear expectations, moderate levels of these indices (typically corresponding to the third quartile) were associated with the lowest risk of depression, conferring a protective effect that diminished or disappeared at extremely high or low levels. Conclusion: In Chinese community-dwelling middle-aged and older adults, moderate visceral adiposity or insulin resistance may be associated with a reduced risk of depression, demonstrating a U-shaped threshold effect. These findings underscore the value of utilizing composite metabolic indices as computational biomarkers for precise mental health screening in aging populations.

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