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Social Desirability and Social Approval Biases in Dietary Self-Report: Examples of Epidemiologic Effect Modification

Social Desirability and Social Approval Biases in Dietary Self-Report: Examples of Epidemiologic Effect Modification. James R. Hebert, ScD. Professor and Chair Department of Epidemiology and Biostatistics Norman J. Arnold School of Public Health University of South Carolina.

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Social Desirability and Social Approval Biases in Dietary Self-Report: Examples of Epidemiologic Effect Modification

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  1. Social Desirability and Social Approval Biases in Dietary Self-Report: Examples of Epidemiologic Effect Modification James R. Hebert, ScD Professor and Chair Department of Epidemiology and Biostatistics Norman J. Arnold School of Public Health University of South Carolina

  2. Other Collaborators: Lynn Clemow, Ph.D. Ira S. Ockene, M.D. Cara B. Ebbeling, Ph.D. Yunsheng Ma, M.D., M.P.H. Thomas G. Hurley, M.Sc. Milagros C. Rosal, Ph.D. Charles E. Matthews, Ph.D. Judith K. Ockene, Ph.D.

  3. You’ve got to be kidding! • cognitive difficulties • emotional aspects issues of prying • misleading responses

  4. Emotional Aspects of Eating - • same part of brain processes sensations of taste, smell, and basic emotional and instinctual behavior. • social messages get overlaid on psychological and emotional ones.

  5. Background Self-report of dietary intake could be biased by social desirability or social approval thus affecting risk estimates in epidemiologic studies. These constructs produce response set biases, which are evident when testing in domains characterized by easily recognizable correct or desirable responses. Given the social and psychological value ascribed to diet, assessment methodologies used most commonly in epidemiologic studies are particularly vulnerable to these biases.

  6. Social Desirability is a Response Set reflecting the defensive tendency to respond in such a way as to avoid criticism in a situation perceived to be a test.

  7. Social Approval is a Response Set reflecting the tendency to actively seek approval in a situation perceived to be a test.

  8. Social desirability bias in dietary self-report may compromise the validity of dietary intake measures. International Journal of Epidemiology 1995; 24: 389-398.

  9. WATCH WORCESTER AREA TRIAL for COUNSELING in HYPERLIPIDEMIA

  10. We Developed Seven-Day Diet Recall (7DDR) In WATCH The 7DDR looks very much like a FFQ, but it asks participants to recall specific meals and snacks over the past week. It includes 118 foods, 13 beverages, and a worksheet. Thus it combines elements of the FFQ and produces estimates of dietary intake more like trait measures than does 24HR.

  11. STUDY DESIGN WATCH External Validation Study 3 Weeks Pre 7DDR Post 7DDR (7 randomly selected 24-Hrs) Exactly two years later social desirability and approval assessed

  12. Hypothesis: Response Set Biases are expressed on structured questionnaires such as the Seven Day Dietary Recall (7DDR) or the FFQ. ¨ it is closed-ended and has obvious correct responses grid-like obvious response categories requires report of diet as a trait rather than a state ¨ ¨

  13. Methods: Social desirability and social approval biases were tested by comparing nutrient scores derived from multiple twenty-four hour diet recalls (24HR) on randomly assigned days with those from two seven-day diet recalls (7DDR) (similar in some respects to commonly used food frequency questionnaires), one administered at the beginning of the test period (pre) and one at the end (post). Statistical analysis included correlation and multiple linear regression. Except for b describing relation between methods (where b should equal 1.0) , H0:b=0.

  14. Social Desirability Approval Assessment Marlowe-Crowne Social Desirability Scale Martin-Larsen Approval Motivation Scale 33-item (true/false) 20-item (5-point Likert)

  15. Summary Statistics (from 24HR) Women (n=27) Men (n=14) Energy (kcal/d) 1491 (62) 1971 (600) Fat (g/d) 51.9 (17.3) 65.1 (23.8) % Fat 31.3 (5.5) 29.4 (4.6) Calcium (mg/d) 668 (277) 785 (218) Cholesterol (mg/d) 185 (65) 261 (195) * Tabulated values are mean (standard deviation)

  16. WATCH – External Validation Study – Summary Statistics Variable % or Mean/SD Female Male (N=27) (N=14) % Married 74.1% 64.3% % White 81.5% 85.7% Age (years) 51.3/16.1 47.2/13.9 Social Desirability Score 20.5/6.4 18.5/5.9 Social Approval Score 48.4/9.6 44.9/9.1 Total energy (k/cal) 1490/461 1970/599 Total fat (g) 51.9/17.3 65.1/23.8

  17. Statistical Model Nutrient test method = Nutrient comparison method + Social Approval + Social Desirability + BMI + Covariates

  18. WATCH – External Validation Study – Regression Results (Pre) 24-HR Score SD Score Total Energy (kcal) b= 0.96 -50.23 SEb = 0.27 22.58 P-value = n.s. (0.06) Total fat (g) 1.41 -2.34 0.39 1.17 n.s. (0.06) Saturated fatty acids (g) 1.35 -0.68 0.29 0.32 n.s. (0.04)

  19. WATCH – External Validation Study – Regression Results (Post) 24-HR Score SD Score Total Energy (kcal) b= 0.97 -25.50 SEb = 0.17 14.49 P-value = n.s. (0.09) Total fat (g) 0.90 -1.18 0.20 0.59 n.s. (0.06) Saturated fatty acids (g) 0.87 -0.30 0.17 0.20 n.s. n.s.

  20. Results of General Linear Models to Assess Gender Differences In Social Desirability Bias Pre Measurements Post Measurements Women Men Women Men b SEb b SEb b SEb b SEb Dependent Variable Total fat(g) -3.36 (1.57) -1.11 (1.79) -2.06 (0.64) -0.35 (1.43) Saturated fatty acids -0.85 (0.45) -0.29 (0.67) -0.62 (0.21) 0.22 (0.49) Total energy (kcal) -68.05 (30.31) -38.90 (32.00) -47.33 (14.35) -17.31 (32.97) Fat (% energy) -0.33 (0.23) -0.13 (0.20) -0.01 (0.22) -0.09 (0.21) Cholesterol -7.17 (2.55) -11.25 (7.56) -3.68 (2.13) 1.48 (6.00)

  21. Results of nutrient quartile stratification to assess variation in social desirability bias Pre Measures Post Measures Dependent Variable b Seb b SEb Fat Quartile 1 -1.11 0.85 -1.15 0.64 Quartile 2 0.33 0.65 -0.29 0.32 Quartile 3 -1.42 1.12 -1.48 0.24 Quartile 4 -3.62 2.95 -1.65 1.08 Total Energy Quartile 1 -18.88 19.56 -22.17 5.76 Quartile 2 6.39 3.42 10.27 4.90 Quartile 3 -22.79 11.22 13.34 24.01 Quartile 4 -72.66 84.96 -13.02 45.27

  22. WATCH – External Validation Study Conclusions: • A downward bias in the 7DDR due to social desirability was observed in women. • It amounted to about 700 kcal/day across the interquartile range of social desirability scores for women Slide 20

  23. WATCH Study Hebert JR, Ma Y, Clemow L, Ockene IS, Saperia G, Stanek EJ, Merriam PA, Ockene JK. Gender differences in social desirability and social approval bias in dietary self report. Am J Epidemiol 1997; 146:1046-1055. • The overall purpose of the Worcester Area Trial for Counseling in Hyperlipidemia was: • To evaluate the effectiveness of a physician-delivered nutrition intervention counseling program in reducing dietary fat and LDL

  24. Data Collection in WATCH Study: • Over 8,000 patients screened to determine eligibility • Age 20-65 years • No prior drug treatment and RD referral • First fingerstick for testing cholesterol • Upper 25% of cholesterol distribution • Second fingerstick • Consent 1,278 patients One year Single 24HR 7DDR 2 lipid profile BMI(kg/m2 ) SD and SA measures March 1995 Baseline Single 24HR 7DDR 2 lipid profiles BMI(kg/m2 )

  25. Responders Vs. Non-Responders Variable Responders Non-responder P-value* MEAN (SD) MEAN (SD) Age (Years) 49.44 (10.63) 48.29 (10.45) 0.06 Baseline BMI 28.80 (5.29) 29.51 (5.90) 0.05 Baseline Blood Cholesterol (mg/dl) 233.60 (46.85) 223.48 (56.59) 0.0008 Baseline LDL Cholesterol (mg/dl) 152.82 (39.39) 148.89 (43.19) 0.01 # of extra lipid measures from Fallon 2.15 (1.26) 1.92 (1.22) 0.01 *P value based on Chi-square for categorical variables and two sample t-test the two group means

  26. Male and Female Comparison Male (n=325) Female (n=434) MEAN SD# MEAN SD# P- value* 7DDR Nutrients at Baseline Total Energy (kcal/d) 2085.63 927.83 1786.32 752.11 0.0001 Total Fat (g/d) 88.22 50.94 77.49 41.76 0.004 % Calories from Fat 37.11 8.96 38.17 8.73 0.12 Saturated Fat (g/d) 29.39 17.66 25.25 13.50 0.0009 % Calories from Saturated Fat 12.38 3.78 12.55 3.44 0.52 *P value based on two sample t-test the difference of two group means

  27. Results of GLM for Males, WATCH Study Independent Variables: Dependent Variables: 24HR SD SCORE AP SCORE BMI Total Fat (g/d) b 0.29 0.70 1.21 1.04 (p) (0.0003) (0.24) (0.01) (0.04) Total Saturated Fat (g/d) b 0.26 0.25 0.45 0.50 (p) (0.0001) (0.23) (0.001) (0.05) Total Energy (kcal/d) b 0.36 9.18 21.50 27.24 (p) (0.0001) (0.38) (0.01) (0.01)

  28. Results of GLM for Females, WATCH Study Independent Variables: Dependent Variables: 24HR SD SCORE AP SCORE BMI Total Fat (g/d) b 0.28 -0.78 -0.01 0.52 (p) (0.0002) (0.07) (0.98) (0.18) Total Saturated Fat (g/d) b 0.26 -0.26 0.02 0.15 (p) (0.0001) (0.05) (0.78) (0.24) Total Energy (kcal/d) b 0.27 -19.16 0.02 8.55 (p) (0.0002) (0.02) (0.99) (0.22)

  29. Some Perspectives • In females: SDSCORE 75th percentile=23, 25th percentile=15, 8 points x 19.16=153.3 kcal energy underreport, or a 6.2g fat underreport • In males: APSCORE 75th percentile=41, 25th percentile=32, 9 points x 21.50=193.5 kcal overreport, or a 10.9g fat overreport

  30. WATCH Social Desirability Study Conclusion • Social desirability was associated with a downward bias in dietary fat and energy intake in females • Social approval was found to be related to over-reporting energy and fat intake in males • Further studies are needed to establish models to adjust for the bias

  31. The Treatwell 5-a-Day Study Hebert JR, Peterson KE, Hurley TG, Stoddard AM, Cohen N, Field AE, Sorensen G. The effect of social desirability trait on self-reported dietary measures among multi-ethnic female health center employees. Ann Epidemiol 2001; 11:417-427. • Multi-ethnic sample of community health center workers • Representing three control sites • Multiple 24HR as “relative criterion” • Uses three methods for comparison, including Harvard/Channing FFQ • Predominantly (~85% women)

  32. The Treatwell 5-a-Day Study – Social Desirability Results by Ethnicity, Women Only Black Hispanic White (n=23) (n=31) (n=30) Variable: b SEb b SEb b SEb Total Energy Intake (kcal/d) 15.1 31.1 18.9 20.0 -4.5 15.9 Total Fat Intake (g/d) 0.64 0.94 1.03 1.07 -0.23 0.62

  33. The Treatwell 5-a-Day Study – Results by Occupational Category, Women Only Non-Professional Professional p-value for (n=52) (n=39) Ho: b <coll = b >coll Variable: b SEb b SEb Total Energy Intake (kcal/d) 31.8 18.5 -20.6 14.5 <0.005 <0.05 Total Fat Intake (g/d) 1.12 -0.19 0.57 0.67 ns Fruit (servings/d) - FFQ 0.011 0.042 -0.004 0.037 ns Fruit (servings/1000kcal/d) -0.008 0.031 0.002 0.029

  34. The Treatwell 5-a-Day Study – Results by Education, Women Only Less Than College College Degree or More p-value for (n=52) H o: b <coll = b >coll (n=39) Variable: b SEb b SEb Total Energy Intake (kcal/d) 36.1 20.0 -23.6 12.8 <0.001 Total Fat Intake (g/d) 1.23 0.78 -0.50 0.41 <0.001 Fruit (servings/d) - FFQ -0.003 0.046 -0.027 0.033 ns Fruit (servings/1000kcal/d) -0.005 0.032 -0.002 0.026 ns

  35. The Treatwell 5-a-Day Study – Conclusions The FFQ also appears to be biased by social desirability in women, but ….. ¨ the critical factor determining the bias is education which is ….. ¨ more important than occupational category or ethnicity/race. ¨ As in the WATCH study, bias is oriented toward fat/energy intake ¨

  36. The Energy Study, Worcester, MA - 1997 Hebert JR, Ebbeling CB, Matthews CE, Ma Y, Clemow L, Hurley TG, Druker S. Systematic errors in middle-aged women's estimates of energy intake: Comparing three self-report measures to total energy expenditure from doubly labeled water. Ann Epidemiol 2001; (In Press):00-000. ¨ First such study to focus on the most widely used FFQ (NCI/WHI) ¨ First study to focus on these biases employing stable isotope methods for comparison (TEE from DLW)

  37. Overview of Study Doubly-Labeled Water Metabolic Period 7 14 0 1 days • Baseline questionnaires • Demographic data • (education) • Social desirability (Marlowe-Crowne Scale, 33-item, true/false) • Food frequency questionnaire • (WHI)

  38. Description of the Study Population, The Energy Study (N=73) n % Married 47 64.4 White 72 98.6 Pre-menopausal 41 56.2 Bachelors Degree or more 33 45.2 Employed Full Time 44 60.3 Professional, Managerial Work 33 55.0 Current Smoker 7 9.6 Sedentary 38 52.1

  39. Further description of the Study Population, The Energy Study (N=73) Interquartile Mean Standard Range Deviation Minimum 25% 75% Maximum Age (years) 49.0 6.8 40 44 53 65 Body Mass (kg) 70.0 10.4 43.9 62.1 76.9 90.5 BMI (kg/m2) 27.1 4.1 18.7 24.5 29.8 38.2 Fat-Free Mass (kg) 42.4 5.1 32.3 38.1 46.3 53.7 Social Desirability Score 17.4 5.9 4.0 15.0 22.0 29.0

  40. Further description of the Study Population, The Energy Study (N=73) Interquartile Mean Standard Range Deviation Minimum 25% 75% Maximum TEE from DLW (kcal/d) 2102 380 1378 1830 2318 3337 24-Hour Recall-Derived Data (7-day average) Energy Intake (kcal/d) 1820 464 1147 1494 2002 3566 Food Quotient 0.90 0.03 0.82 0.88 0.92 0.99 FFQ Energy (kcal/d) Day-0 Administration 1735 764 429 1229 2089 4986 Day-14 Administration 1622 594 639 1186 2028 3703

  41. Social Desirability Bias (kcal/day/point) by Education Level (FFQ-Derived Energy Intake Versus TEE from DLW, Beginning of Metabolic Period), The Energy Study (N=73). All Education Levels: -36.6 (-65.7, -7.5) Whole Sample (n=73) -12.2 (-34.7, 13.1) Excluding “Outliers ” (n=69) High Education (college +) Whole Sample (n=33) -73.3 (-113., -32.9) -31.9 (-63.6, -0.2) Excluding “Outliers ” (n=31)

  42. Social Desirability Bias (kcal/day/point) by Education Level (FFQ-Derived Energy Intake Versus TEEfrom DLW, End of Metabolic Period), The Energy Study (N=73). All Education Levels: -10.8 (-34.7, 13.1) Whole Sample (n=73) Excluding “Outliers ” (n=72) -13.7 (-35.8, 8.4) High Education (college +) Whole Sample (n=33) -21.8 (-53.5, 9.9)

  43. Social Desirability Bias 50 25 0 -25 Bias (kcal/day/point) -50 -75 Beginning -100 End -125 -150 Education Whole Sample (n=75) High (n=33) Low (n=42)

  44. Revisiting WATCH --- Why? Hebert JR, Ma Y, Ebbeling CB, Matthews CE, Ockene IS. Self-report data. Compliance in Healthcare and Research. Armonk, NY: Futura, 2001:163-179. Is there an effect of education when cut at college+? ¨ What happens with these biases after an intervention? ¨

  45. Social Approval Bias in Males, by Education, WATCH Study, Worcester, Massachusetts, 1991-1995. < College (n=150) Social Approval BMI Score Baseline Total Energy (kcal/day) 29.8 (0.003) 29.1 (0.07) Total Fat (g/day) 1.63 (0.004) 1.60 (0.07) Total SFA (g/day) 0.59 (0.003) 0.53 (0.09) One-year < College (n=112) Total Energy (kcal/day) 36.7 (0.0003) 53.4 (0.001) Total Fat (g/day) 1.50 (0.004) 1.72 (0.04) Total SFA (g/day) 0.41 (0.02) 0.57 (0.05)

  46. Social Approval Bias in Males, by Education, WATCH Study, Worcester, Massachusetts, 1991-1995. ³ College (n=70) Social Approval BMI Score Baseline Total Energy (kcal/day) 8.6 (0.49) 48.6 (0.05) Total Fat (g/day) 0.58 (0.39) 3.87 (0.05) Total SFA (g/day) 0.26 (0.26) 1.34 (0.07) One-year ³ College (n=56) Total Energy (kcal/day) 19.9 (0.14) 33.7 (0.14) Total Fat (g/day) 1.05 (0.11) 0.70 (0.52) Total SFA (g/day) 0.25 (0.18) 0.15 (0.63)

  47. Social Approval and Social Desirability Bias in Females, by Education, WATCH Study, Worcester, Massachusetts, 1991-1995. < College (n=220) Social Approval Social Desirability BMI Score Score Baseline Total Energy (kcal/day) -0.2 (0.97) -14.8 (0.14) 6.9 (0.43) Total Fat (g/day) -0.02 (0.95) -0.53 (0.34) 0.25 (0.61) Total SFA (g/day) 0.03 (0.76) -0.14 (0.45) 0.05 (0.75) One-year < College (n=172) Total Energy (kcal/day) 11.0 (0.07) -3.6 (0.77) 11.1 (0.32) Total Fat (g/day) 0.36 (0.32) -0.57 (0.43) 0.36 (0.58) Total SFA (g/day) 0.14 (0.21) -0.15 (0.52) 0.21 (0.32)

  48. Social Approval and Social Desirability Bias in Females, by Education, WATCH Study, Worcester, Massachusetts, 1991-1995. ³ College (n=64) Social Approval Social Desirability BMI Score Score Baseline Total Energy (kcal/day) -2.9 (0.72) -24.3 (0.04) 19.7 (0.11) Total Fat (g/day) -0.34 (0.49) -1.28 (0.07) 1.42 (0.05) Total SFA (g/day) -0.10 (0.52) -0.53 (0.01) 0.41 (0.07) One-year ³ College (n=53) Total Energy (kcal/day) -5.1 (0.61) -9.5 (0.54) 35.5 (0.04) Total Fat (g/day) -0.23 (0.67) -0.21 (0.80) 1.98 (0.02) Total SFA (g/day) -0.06 (0.74) -0.05 (0.86) 0.75 (0.01)

  49. WATCH Study Conclusions: Education modifies the effect of the social desirability and social approval ¨ The effects differ by gender ¨ There appears to be a differential effect of the intervention on the bias according to gender and education ¨

  50. The Role of Social Desirability in Epidemiologic Confounding SD Score Psychologic Predispositions Physiologic Responses (e.g., Immune Function) Disease True Diet Reported Diet

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