Longitudinal relationship between weight-adjusted waist index and depressive symptoms in middle-aged and older Chinese adults: A prospective cohort study.

Background: The association between obesity and depressive symptoms remains controversial. The Weight-adjusted waist index (WWI) shows advantages in assessing central obesity. This study aimed to investigate the longitudinal relationship between WWI and depressive symptoms.

Method: This prospective cohort study utilized data from the China Health and Retirement Longitudinal Study (CHARLS) spanning 2011-2020. Depressive symptoms were assessed using the 10-item Center for Epidemiological Studies Depressive Symptoms Scale (CESD-10) scores. Linear mixed models were used to examine longitudinal associations.

Results: A total of 6835 participants over the age of 45 were included. WWI was positively associated with CESD-10 scores (β per 1 SD increase = 0.052SD; 95%CI: 0.021 to 0.083SD) and was linked to a faster increase in CESD-10 scores over time (β = 0.095SD/year; 95%CI: 0.090 to 0.100 SD/year). Conversely, BMI was negatively associated with CESD-10 scores (β per 1 SD increase = -0.067SD; 95%CI: -0.097 to -0.038SD). However, the negative association between BMI and CESD-10 scores weakened over time (β per 1 SD increase = 0.008SD/y; 95%CI: 0.003 to 0.013 SD/y). Nonlinear associations were detected between both WWI and BMI with CESD-10 scores.

Limitations: Self-reported depressive symptoms assessments may have introduced information bias. The observational design limits ruling out unobserved confounding factors.

Conclusions: Our findings highlight the association between WWI and the long-term progression of depressive symptoms in middle-aged and older adults. WWI may enhance our understanding of the link between obesity and depressive symptoms and could be superior to BMI in predicting depressive symptom progression.