Analyzing the Association Between Depressive Symptoms and Weight-Adjusted Waist Index

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CASE VIGNETTE

“Ms Gray” is a 42-year-old Caucasian woman with a 15-year history of severe, recurrent major depressive disorder with psychotic features and considerable anxiety symptoms. She does not drink, smoke, or use illicit drugs. She meets criteria for obesity and has a body mass index (BMI) of 33. She currently takes a selective serotonin reuptake inhibitor and receives cognitive behavioral therapy from a psychologist.

At an outpatient clinic visit, Ms Gray reports an increased interest in exercise. She says she plans to walk in the morning with a neighbor friend. She asks about the potential beneficial effects of exercise on her depression. As her psychiatrist, how would you respond?

Depression is the leading cause of disability worldwide.¹ Obesity is a replicated risk factor for the onset of depressive symptoms, with a magnitude of greater than 50%.² Conventional measures of obesity include BMI and waist circumference (WC). However, BMI does not distinguish between visceral fat and muscle mass; similarly, WC does not distinguish between visceral and subcutaneous fat.

Weight-adjusted waist index (WWI) has been proposed as a new index of obesity reflecting central obesity, which standardizes WC to better reflect adiposity and muscularity.³ However, the relationship between WWI and depressive symptoms is unknown.

The Current Study

Liu and colleagues⁴ investigated associations between WWI and depressive symptoms in the National Health and Nutrition Examination Survey (NHANES) and made comparisons to traditional obesity indices. NHANES data are freely available in the public domain. Data were included for 32,374 participants from seven 2-year cycles (2005-2018). Patients were excluded if they were younger than 20 years of age, pregnant, and in cases where there was missing data on WC, weight, and/or depressive symptoms. WWI is calculated as the ratio of WC (in cm) to the square root of weight (in kg; ie, WWI = WC / √ [weight]).

Depressive symptoms were assessed using Patient Health Questionnaire-9 (PHQ-9). Additional covariates included age, sex, race/ethnicity, smoking, diabetes, hypertension, alcohol consumption, household income, education level, lipid panel, WC, BMI, and poverty rate. Differences in demographic variables by WWI quartiles were investigated with t-tests and chi-squared tests. Linear associations between WWI, WC, BMI, and depressive symptoms were analyzed using weighted multiple linear regression and logistic regression.

The mean participant age was 50 years, 50% of participants were male, and 43% were non-Hispanic White. The mean WWI was 11.1 ± 0.9. There were 2810 participants (9%) with PHQ-9 scores greater than or equal to 10, which was used as the definition of depressive symptoms. Higher quartiles of WWI were more likely to be women, non-Hispanic White, Mexican American, and smokers, and to drink more alcohol and have diabetes and hypertension. Higher WWI was also associated with higher total and low-density lipoprotein cholesterol, triglycerides, BMI, and WC, as well as lower education and high-density lipoprotein cholesterol.

In a regression model adjusting for age, sex, race/ethnicity, smoking, diabetes, hypertension, alcohol consumption, household income, education level, lipid panel, and poverty rate, the WWI (as a continuous measure) was associated with depressive symptoms (OR = 1.18; 95% CI, 1.05-1.34) more strongly than either BMI or WC (OR = 1.01 for both). After controlling for potential confounders, participants in the highest quartile of WWI were almost 1.5 times more likely to have depressive symptoms vs those in the lowest quartile (OR = 1.49; 95% CI, 1.14-1.96). Subgroup analyses indicated that this association was not moderated by age, sex, race/ethnicity, smoking, diabetes, or hypertension.

Study Conclusions

The investigators concluded that WWI was robustly associated with depressive symptoms, with a significantly higher magnitude than either BMI or WC. Study strengths include the use of a large, nationally representative study sample and consideration of many potential confounding factors. Study limitations include the cross-sectional design (which limits causal inferences), the use of a self-report depression measure, and the absence of information on the duration of depressive symptoms and antidepressant treatments.

The Bottom Line

The WWI was a stronger predictor of depressive symptoms than either BMI or WC. The WWI represents a potentially useful measure in clinical practice.

Dr Miller is a professor in the Department of Psychiatry and Health Behavior at Augusta University in Georgia. He is on the editorial board and serves as the schizophrenia section chief for Psychiatric Times. The author reports that he receives research support from Augusta University, the National Institute of Mental Health, and the Stanley Medical Research Institute.

References

1. Charlson F, van Ommeren M, Flaxman A, et al. New WHO prevalence estimates of mental disorders in conflict settings: a systematic review and meta-analysis. Lancet. 2019;394(10194):240-248.

2. Luppino FS, de Wit LM, Bouvy PF, et al. Overweight, obesity, and depression: a systematic review and meta-analysis of longitudinal studies. Arch Gen Psychiatry. 2010;67(3):220-229.

3. Park Y, Kim NH, Kwon TY, Kim SG. A novel adiposity index as an integrated predictor of cardiometabolic disease morbidity and mortality. Sci Rep. 2018;8(1):16753.

4. Liu H, Zhi J, Zhang C, et al. Association between weight-adjusted waist index and depressive symptoms: a nationally representative cross-sectional study from NHANES 2005 to 2018. J Affect Disord. 2024;350:49-57.