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

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

3. 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.

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

5. 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

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

7. Sample Used for Analyses
Initial NHANES 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

8. 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

9. 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

10. Body Mass Index (BMI) (NHLBI Cut-points) Independent Variable
Underweight: <18.5
Normal Weight: (referent)
Overweight:
Class I Obesity:
Class II Obesity:
Class III Obesity: > 40

11. 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

12. 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

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

14. 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
Referent
1.09
0.52, 2.28
1.16
0.47, 2.83
0.78
0.25, 2.38
1.34
0.62, 2.88
1.18
0.62, 2.25
0.69
0.30, 1.57
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

15. 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
Referent
0.56
0.26, 1.22
0.67
0.36, 1.25
0.49
0.24, 1.00
1.17
0.29, 4.63
0.33, 5.97
0.26, 3.89
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

16. 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
2.20
1.10, 4.39
1.82
0.86, 3.98
1.47
0.40, 5.39

17. 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

18. 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

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

20. 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.