Keypoint: A more useful measure than BMI or waist circumference? Researchers analyzed the association between weight-adjusted waist index and depressive symptoms.
CASE VIGNETTE
“Ms Gray” is a 42-year-old Caucasian female with a 15-year history of recurrent, severe major depressive disorder (MDD) with psychotic features. She also has significant symptoms of anxiety. She does not smoke, drink alcohol, or use illicit drugs. She meets the criteria for obesity, with a current body mass index (BMI) of 33. She currently takes a selective serotonin reuptake inhibitor and sees a psychologist for cognitive-behavioral therapy.
At an outpatient clinic visit, she reports 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 >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 with traditional obesity indices. NHANES data are freely available in the public domain. Data were included for 32,374 participants from 7 2-year cycles (2005 to 2018). Exclusion criteria were age <20 years, pregnancy, and 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 the Patient Health Questionnaire (PHQ-9). Additional covariates included age, sex, race/ethnicity, smoking, diabetes, hypertension, alcohol consumption, household income, education level, lipid panel, WC, BMI, and the poverty rate. Differences in demographic variables by WWI quartiles were investigated with t-tests and chi-square 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 ≥10, which was used as the definition of depressive symptoms. Higher quartiles of WWI were more likely to be female, 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 LDL cholesterol, triglycerides, BMI, and WC, and lower education and HDL cholesterol.
In a regression model adjusting for age, sex, race/ethnicity, smoking, diabetes, hypertension, alcohol consumption, household income, education level, lipid panel, and the 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). Participants in the highest (versus lowest) quartile of WWI were almost 1.5 times more likely to have depressive symptoms, after controlling for potential confounders (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 weight-adjusted weight index was a stronger predictor of depressive symptoms than either BMI or WC. The WWI represents a potentially useful measure in clinical practice.
Note: This article originally appeared on Psychiatric Times
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