Associations between Depression and Obesity: Findings from the National Health and Nutrition Examination Survey, 2005-2006 Arlene Keddie, Ph.D. Assistant Professor of Epidemiology Northern Illinois University November 8, 2010 APHA 138th Annual Meeting

Arlene Keddie No relationships to disclose Presenter Disclosure Arlene Keddie No relationships to disclose

Brief Background Evidence for associations between depression and obesity inconsistent. Depression increases risk of CVD and NIDDM, especially in women. Obesity is an established risk factor for both CVD and NIDDM If obesity is associated with depression, this might help explain why depression is linked to these other conditions.

Why is it important to know if depression is associated with obesity? Diabetes CVD

Objectives To investigate the association between body mass index (BMI) and depression in a diverse national sample of American adults To investigate gender and severity of obesity as modifiers of the association between depression and BMI To determine if waist circumference (WC) is associated with depression To explore whether health behaviors or poor physical health are mediators of the association between depression and BMI or WC

Continuous NHANES 2005-2006 Continuous NHANES 2005-2006 Oversampled Released in two year cycles since 1999 2005-2006 Oversampled African Americans Mexican Americans people with low income people aged 60+

Sample Used for Analyses Initial NHANES 2005-2006 Sample of 10,348 people Removed 5,369 children <20 years old 4,979 people aged 20+ Removed 440 pregnant women or with unknown pregnancy status 4,539 non-pregnant adults aged 20+ Removed 940 with missing data 3,599 Non-Pregnant Adults Aged > 20 with Complete Data

Depression: Patient Health Questionnaire (PHQ-9) Dependent Variable Nine 4-point Likert questions based on the 9 signs and symptoms from the DSM-IV Scale of 0-27 for these 9 questions 10th question to indicate extent of impairment in daily life

To be Depressed one must: Have PHQ-9 score of >10 Have answered at least one of these two items positively: Little interest or pleasure in doing things Feeling down, depressed or hopeless Indicate some level of impairment in work or social roles because of these symptoms

Body Mass Index (BMI) (NHLBI Cut-points) Independent Variable Underweight: <18.5 Normal Weight: 18.5-24.9 (referent) Overweight: 25-29.9 Class I Obesity: 30-34.9 Class II Obesity: 35-39.9 Class III Obesity: > 40

Waist Circumference (WC) (NIH Cut-points) Independent Variable Men < 102 centimeters = Small WC (referent) > 102 centimeters = Large WC Women < 88 centimeters = Small WC (referent) > 88 centimeters = Large WC

Demographic Variables Behavioral and Health Variables Covariates Demographic Variables Behavioral and Health Variables Age Gender Race/Ethnicity Education Income Marital Status Smoking Alcohol Consumption Physical Activity Self-Rated Health Status No. of Chronic Conditions

Logistic Regression Models Statistical Analysis Logistic Regression Models Unadjusted Adjusted for Demographic and Behavioral Variables Adjusted for Demographic and Health Variables

Results: Odds of Depression in Women 2 to 4 Fold Association BMI or WC Model 1: Unadjusted Model 2: Demographic and Behavioral Variables Model 3: Demographic and Health Variables Waist Circumference Odds Ratio 95% Confidence Interval 95% Confidence Interval Odds Ratio < 88 1.00 referent >88 2.23 1.15, 4.33 1.98 1.07, 3.68 1.13 0.58, 2.19 BMI 18.5-24.9 Referent 25-29.9 1.09 0.52, 2.28 1.16 0.47, 2.83 0.78 0.25, 2.38 30-34.9 1.34 0.62, 2.88 1.18 0.62, 2.25 0.69 0.30, 1.57 35-39.9 1.71 0.83, 3.53 1.38 0.58, 3.32 0.53 0.23, 1.22 40+ 4.92 1.91, 12.7 4.20 1.28, 13.74 2.18 0.80, 5.91

Results: Odds of Depression in Men No Association with BMI or WC Model 1: Unadjusted Model 2: Demographic and Behavioral Variables Model 3: Demographic and Health Variables Waist Circumference Odds Ratio 95% Confidence Interval Confidence Interval < 102 1.00 referent >102 1.75 0.67, 4.56 1.83 0.71, 4.77 1.41 0.56, 3.54 BMI 18.5-24.9 Referent 25-29.9 0.56 0.26, 1.22 0.67 0.36, 1.25 0.49 0.24, 1.00 30-34.9 1.17 0.29, 4.63 0.33, 5.97 0.26, 3.89 35-39.9 2.41 0.61, 9.57 2.88 0.73, 11.36 1.56 0.38, 6.46 40+ 1.73 0.26, 11.43 2.08 0.33, 13.05 0.81 0.13, 5.02

Men and Women Combined: Association of Depression and Large Waist Circumference Model 1: Unadjusted Model 2: Demographic and Behavioral Variables Model 3: Demographic and Health Variables Odds Ratio 95% Confidence Interval 95% Confidence Interval Total Sample Small WC 1.00 referent Large WC 2.07 1.24, 3.45 1.97 1.17, 3.32 1.33 0.77, 2.32 BMI 25-29.9 2.20 1.10, 4.39 1.82 0.86, 3.98 1.47 0.40, 5.39

How might poor physical health mediate associations between depression and obesity? Chronic Conditions Poor Physical Health Depression Depression Poor Health Behaviors Poor Physical Health Obesity

Limitations Cross-sectional studies cannot establish causality. Possible Selection Bias Those with missing data (20.7% of eligible) Less Educated Racial/Ethnic Minorities Older Physically Inactive Lower Income Poor or Fair Health

Strengths Well-measured variables Controlled for a variety of possible confounders/mediators Recent ethnically varied national sample Examined both BMI and WC

Conclusions Depression High WC, especially among women Depression Class III obesity among women Why only in women? Poor physical health should be further investigated as a possible mediator.