This article was downloaded by: [New York University] On: 10 February 2015, At: 08:47 Publisher: Routledge Informa Ltd Registered in England and Wales Registered Number: 1072954 Registered office: Mortimer House, 37-41 Mortimer Street, London W1T 3JH, UK
Nutrition and Cancer Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/hnuc20
Differential misclassification bias and dietary recall for the distant past using a food frequency questionnaire a
b
Thomas Gregory Hislop , Charles W. Lamb & Vincent T.Y. Ng
a
a
Cancer Control Agency of British Columbia , 600 West 10th Avenue, Vancouver, British Columbia, Canada , V5Z 4E6 b
Department of Mathematics , University of British Columbia , Vancouver, British Columbia, Canada , V6T 1Y4 Published online: 04 Aug 2009.
To cite this article: Thomas Gregory Hislop , Charles W. Lamb & Vincent T.Y. Ng (1990) Differential misclassification bias and dietary recall for the distant past using a food frequency questionnaire, Nutrition and Cancer, 13:4, 223-233, DOI: 10.1080/01635589009514064 To link to this article: http://dx.doi.org/10.1080/01635589009514064
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Differential Misclassification Bias and Dietary Recall for the Distant Past Using a Food Frequency Questionnaire Downloaded by [New York University] at 08:47 10 February 2015
Thomas Gregory Hislop, Charles W. Lamb, and Vincent T.Y. Ng
Abstract Cases (n = 263) and controls (n = 200) returned self-administered food frequency questionnaires in 1980-1982 and again in 1986 as part of a case-control study of breast cancer. The questionnaires asked about consumption of specific food items as recalled for four different age periods. K-statistics comparing responses in the first and second questionnaires were generally similar for cases and controls and were consistent across the different age periods. The influence of recent dietary change on dietary recall diminished for the more distant past. The food frequency questionnaire was found to be more reliable for specific food items for the distant past than for the more recent past. Differential misclassification bias between cases and controls was less apparent for the more distant past. The frequency and interpretation of missing values is discussed. (Nutr Cancer 13, 223-233, 1990)
Introduction
Considering the likelihood of tempciral changes in dietary habits and the long latency period for cancer development, it is important for epidemiological studies of diet and cancer to examine the accuracy of dietary data, for the distant past. Because a true standard is not known for long-term diet, accuracy has been measured by reliability studies. Studies have shown that reliability of recall for individual food items is much greater than would be expected by chance alone (1). It has also been shown that the best estimate for past diet is obtained by focusing on the past time period rather than on the current diet (2). It is not known to what extent differential misclassification due to bias in dietary recall exists between cases and controls; nor it is known if this bias is enhanced or reduced by enquiring about diet from the distant past. Differential misclassification bias is potentially a T. G. Hislop and V. T. Y. Ng are affiliated with the Cancer Control Agency of British Columbia, 600 West 10th Avenue, Vancouver, British Columbia, Canada V5Z 4E6. C. W. Lamb is affiliated with the Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Y4.
Copyright © 1990, Lawrence Erlbaum Associates, Inc.
more serious problem than is random error in dietary recall (2). This paper examines the reliability of dietary recall for different age periods in the past using a food frequency questionnaire that was administered as part of a case-control study of breast cancer (3). Cases and controls are examined separately. The interpretation of missing values for food items on the questionnaire is also investigated.
Downloaded by [New York University] at 08:47 10 February 2015
Method
A population-based case-control study of breast cancer was undertaken in British Columbia from 1980 to 1982. Eligible cases included women under 70 years of age who were registered with the British Columbia Cancer Registry during this period. Controls were selected from the neighbors or acquaintances of the cases; any control with a personal history of breast cancer was excluded. For this paper, cases and controls were restricted to those over 40 years of age at entry into the original study in 1980-1982 and who had completed the dietary section of a self-administered questionnaire. This mailed questionnaire included a dietary section along with questions on family history, reproductive and medical history, estrogen use, and other risk factors for breast cancer. The dietary section included a food frequency questionnaire to be completed for four different age periods to allow for major changes in life circumstances that might have influenced eating habits; these age periods were childhood (less than 13 yrs), teens (13-19 yrs), younger adulthood (20-39 yrs), and older adulthood (over 40 yrs). Women were instructed "to try and recall, at least roughly, some general eating patterns at younger ages." Respondents were asked to categorize their usual frequency of consumption as "daily, 3-6 times per week, 1-2 times per week, 1-3 times per month, or less than once per month" for 31 specific food items that were selected because of their fat or vitamin content (Table 1). In a separate part of the dietary section, women were asked how frequently they usually consumed beef, pork, chicken (including other poultry), and fish (including shellfish) prior to a stated reference date (i.e., the date of diagnosis of breast cancer in the case). The categories of consumption were "at least once a day, at least once a week, less often, and never." In 1986, a second dietary questionnaire was sent to 298 and 243 of these original cases and Table 1. Specific Food Items by Food Group Meat products Hamburger Bacon, ham Sausage, salami Fried sausage Visible fat on meat Gravy, drippings Other fatty meats Vegetable oils Salad oils, dressings Oil fried foods Margarine Peanut butter Other sources of vegetable oils Dairy Products Butter Cream Cheese Ice cream Whole milk
224
Vegetables Cabbage, brussels sprouts, kale Broccoli, cauliflower Green pepper Lettuce Spinach, greens (beet/turnip) Other green vegetables Carrots Squash, pumpkin Turnips Other yellow vegetables Potatoes Fruit Citrus fruit (oranges, tangerines, grapefruit, lemons, limes) Berries Tomatoes
Nutrition and Cancer 1990
Downloaded by [New York University] at 08:47 10 February 2015
controls, respectively, who could be located and who were over age 40 years at study entry in 1980-1982. This questionnaire included a section for past consumption patterns that was identical to that in the 1980-1982 questionnaire and a section for recent consumption (i.e., "usual eating habits in the past year"). Because the questionnaire sent in 1986 was restricted to diet, it was much shorter than that ;;ent in 1980-1982. The analysis of the frequency of consumption, using an ordinal scale, considered all 31 food items over the four age periods and usual consumption of beef, pork, chicken, and fish. The focus of analysis was on reliability (4). Trend difference for individual responses to specific items were studied by the Wilcoxon matched-pairs signed-rank test. Weighted K-statistics (with quadratic weights) were used to measure the reliability of responses, and the Spearman correlation coefficient was employed to investigate how changes in recent eating habits may influence reported consumption in the distant past. The Mann-Whitney test was used to see if differences existed between those who responded and those who did not respond on the first questionnaire. Finally, the McNemar test was used to look at possible trends in missing value patterns. Results Of the eligible women sent a second dietary questionnaire in 1986,263 cases (88%) and 200 controls (82%) returned completed questionnaires.
Reliability
The comparisons to examine reliability were restricted to women with no missing values for the particular food item in either the first (1980-1982) or second (1986-1987) questionnaire. K-Statistics were used to measure the reliability of responses for specific food items. Before doing this, however, we first tested for systematic trend differences for food items at different age periods by comparing responses in the first and second questionnaires. For most food items there were no significant trend differences in responses between the two questionnaires. Table 2 presents the food items with statistically significant trend differences at p < 0.01. Food items with borderline statistically significant trend differences (p = 0.01-0.05) for cases included salad oils and turnips in childhood; oil fried foods, butter, carrots, other yellow vegetables, and berries in teens; salad oils, oil fried foods, broccoli, and carrots in younger adulthood; and fried sausage, gravy, other fatty meats, cream, lettuce, carrots, squash, turnips, other yellow vegetables, and tomatoes in older adulthood. For controls the food items included tomatoes in childhood and salad oils in younger adulthood. Significant differences were most frequently noted for the more recent past (older adulthood) in cases, with more frequent consumption being recalled in the first questionnaire for all food items except carrots and broccoli. Perhaps this reflects the effect of current diet in recalling eating patterns for the more recent past, because cases are more likely to have altered their diets (by reducing fat intake and increasing vegetable consumption) as a consequence of their disease and its treatment. Citrus fruit was the only food item with highly significant trend differences across all four age periods in both cases and controls. Table 3 lists the weighted K-values for specific food items, comparing responses on the first (1980-1982) and second (1986-19H7) questionnaires. Food items with significant trend differences in response between the two questionnaires were not examined. In general, the K-statistics were similar for cases and controls and were consistent across the different age periods. The recall of frequency of consumption for the past was to some extent influenced by changes in recent consumption patterns for both cases and controls. Table 4 shows the correlation coefficients for the food items and age periods in which change in recent consumption had a significant influence on the recalled consumption for the distant past,
Vol. 13, No. 4
225
Table 2. Significant Trend Differences in the Response to Specific Food Items Between the 1980-1982 and 1986-1987 Questionnaires" Age Period
Downloaded by [New York University] at 08:47 10 February 2015
Cases Childhood
Food Item
No. of Pairs Examined
P Value (Two-Tailed)
Lettuce Spinach Other green vegetables Citrus fruit
185
< 0.001 0.002 < 0.001
Nutrition and Cancer Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/hnuc20
Differential misclassification bias and dietary recall for the distant past using a food frequency questionnaire a
b
Thomas Gregory Hislop , Charles W. Lamb & Vincent T.Y. Ng
a
a
Cancer Control Agency of British Columbia , 600 West 10th Avenue, Vancouver, British Columbia, Canada , V5Z 4E6 b
Department of Mathematics , University of British Columbia , Vancouver, British Columbia, Canada , V6T 1Y4 Published online: 04 Aug 2009.
To cite this article: Thomas Gregory Hislop , Charles W. Lamb & Vincent T.Y. Ng (1990) Differential misclassification bias and dietary recall for the distant past using a food frequency questionnaire, Nutrition and Cancer, 13:4, 223-233, DOI: 10.1080/01635589009514064 To link to this article: http://dx.doi.org/10.1080/01635589009514064
PLEASE SCROLL DOWN FOR ARTICLE Taylor & Francis makes every effort to ensure the accuracy of all the information (the “Content”) contained in the publications on our platform. However, Taylor & Francis, our agents, and our licensors make no representations or warranties whatsoever as to the accuracy, completeness, or suitability for any purpose of the Content. Any opinions and views expressed in this publication are the opinions and views of the authors, and are not the views of or endorsed by Taylor & Francis. The accuracy of the Content should not be relied upon and should be independently verified with primary sources of information. Taylor and Francis shall not be liable for any losses, actions, claims, proceedings, demands, costs, expenses, damages, and other liabilities whatsoever or howsoever caused arising directly or indirectly in connection with, in relation to or arising out of the use of the Content. This article may be used for research, teaching, and private study purposes. Any substantial or systematic reproduction, redistribution, reselling, loan, sub-licensing, systematic supply, or distribution in any form to anyone is expressly forbidden. Terms & Conditions of access and use can be found at http://www.tandfonline.com/page/termsand-conditions
Differential Misclassification Bias and Dietary Recall for the Distant Past Using a Food Frequency Questionnaire Downloaded by [New York University] at 08:47 10 February 2015
Thomas Gregory Hislop, Charles W. Lamb, and Vincent T.Y. Ng
Abstract Cases (n = 263) and controls (n = 200) returned self-administered food frequency questionnaires in 1980-1982 and again in 1986 as part of a case-control study of breast cancer. The questionnaires asked about consumption of specific food items as recalled for four different age periods. K-statistics comparing responses in the first and second questionnaires were generally similar for cases and controls and were consistent across the different age periods. The influence of recent dietary change on dietary recall diminished for the more distant past. The food frequency questionnaire was found to be more reliable for specific food items for the distant past than for the more recent past. Differential misclassification bias between cases and controls was less apparent for the more distant past. The frequency and interpretation of missing values is discussed. (Nutr Cancer 13, 223-233, 1990)
Introduction
Considering the likelihood of tempciral changes in dietary habits and the long latency period for cancer development, it is important for epidemiological studies of diet and cancer to examine the accuracy of dietary data, for the distant past. Because a true standard is not known for long-term diet, accuracy has been measured by reliability studies. Studies have shown that reliability of recall for individual food items is much greater than would be expected by chance alone (1). It has also been shown that the best estimate for past diet is obtained by focusing on the past time period rather than on the current diet (2). It is not known to what extent differential misclassification due to bias in dietary recall exists between cases and controls; nor it is known if this bias is enhanced or reduced by enquiring about diet from the distant past. Differential misclassification bias is potentially a T. G. Hislop and V. T. Y. Ng are affiliated with the Cancer Control Agency of British Columbia, 600 West 10th Avenue, Vancouver, British Columbia, Canada V5Z 4E6. C. W. Lamb is affiliated with the Department of Mathematics, University of British Columbia, Vancouver, British Columbia, Canada V6T 1Y4.
Copyright © 1990, Lawrence Erlbaum Associates, Inc.
more serious problem than is random error in dietary recall (2). This paper examines the reliability of dietary recall for different age periods in the past using a food frequency questionnaire that was administered as part of a case-control study of breast cancer (3). Cases and controls are examined separately. The interpretation of missing values for food items on the questionnaire is also investigated.
Downloaded by [New York University] at 08:47 10 February 2015
Method
A population-based case-control study of breast cancer was undertaken in British Columbia from 1980 to 1982. Eligible cases included women under 70 years of age who were registered with the British Columbia Cancer Registry during this period. Controls were selected from the neighbors or acquaintances of the cases; any control with a personal history of breast cancer was excluded. For this paper, cases and controls were restricted to those over 40 years of age at entry into the original study in 1980-1982 and who had completed the dietary section of a self-administered questionnaire. This mailed questionnaire included a dietary section along with questions on family history, reproductive and medical history, estrogen use, and other risk factors for breast cancer. The dietary section included a food frequency questionnaire to be completed for four different age periods to allow for major changes in life circumstances that might have influenced eating habits; these age periods were childhood (less than 13 yrs), teens (13-19 yrs), younger adulthood (20-39 yrs), and older adulthood (over 40 yrs). Women were instructed "to try and recall, at least roughly, some general eating patterns at younger ages." Respondents were asked to categorize their usual frequency of consumption as "daily, 3-6 times per week, 1-2 times per week, 1-3 times per month, or less than once per month" for 31 specific food items that were selected because of their fat or vitamin content (Table 1). In a separate part of the dietary section, women were asked how frequently they usually consumed beef, pork, chicken (including other poultry), and fish (including shellfish) prior to a stated reference date (i.e., the date of diagnosis of breast cancer in the case). The categories of consumption were "at least once a day, at least once a week, less often, and never." In 1986, a second dietary questionnaire was sent to 298 and 243 of these original cases and Table 1. Specific Food Items by Food Group Meat products Hamburger Bacon, ham Sausage, salami Fried sausage Visible fat on meat Gravy, drippings Other fatty meats Vegetable oils Salad oils, dressings Oil fried foods Margarine Peanut butter Other sources of vegetable oils Dairy Products Butter Cream Cheese Ice cream Whole milk
224
Vegetables Cabbage, brussels sprouts, kale Broccoli, cauliflower Green pepper Lettuce Spinach, greens (beet/turnip) Other green vegetables Carrots Squash, pumpkin Turnips Other yellow vegetables Potatoes Fruit Citrus fruit (oranges, tangerines, grapefruit, lemons, limes) Berries Tomatoes
Nutrition and Cancer 1990
Downloaded by [New York University] at 08:47 10 February 2015
controls, respectively, who could be located and who were over age 40 years at study entry in 1980-1982. This questionnaire included a section for past consumption patterns that was identical to that in the 1980-1982 questionnaire and a section for recent consumption (i.e., "usual eating habits in the past year"). Because the questionnaire sent in 1986 was restricted to diet, it was much shorter than that ;;ent in 1980-1982. The analysis of the frequency of consumption, using an ordinal scale, considered all 31 food items over the four age periods and usual consumption of beef, pork, chicken, and fish. The focus of analysis was on reliability (4). Trend difference for individual responses to specific items were studied by the Wilcoxon matched-pairs signed-rank test. Weighted K-statistics (with quadratic weights) were used to measure the reliability of responses, and the Spearman correlation coefficient was employed to investigate how changes in recent eating habits may influence reported consumption in the distant past. The Mann-Whitney test was used to see if differences existed between those who responded and those who did not respond on the first questionnaire. Finally, the McNemar test was used to look at possible trends in missing value patterns. Results Of the eligible women sent a second dietary questionnaire in 1986,263 cases (88%) and 200 controls (82%) returned completed questionnaires.
Reliability
The comparisons to examine reliability were restricted to women with no missing values for the particular food item in either the first (1980-1982) or second (1986-1987) questionnaire. K-Statistics were used to measure the reliability of responses for specific food items. Before doing this, however, we first tested for systematic trend differences for food items at different age periods by comparing responses in the first and second questionnaires. For most food items there were no significant trend differences in responses between the two questionnaires. Table 2 presents the food items with statistically significant trend differences at p < 0.01. Food items with borderline statistically significant trend differences (p = 0.01-0.05) for cases included salad oils and turnips in childhood; oil fried foods, butter, carrots, other yellow vegetables, and berries in teens; salad oils, oil fried foods, broccoli, and carrots in younger adulthood; and fried sausage, gravy, other fatty meats, cream, lettuce, carrots, squash, turnips, other yellow vegetables, and tomatoes in older adulthood. For controls the food items included tomatoes in childhood and salad oils in younger adulthood. Significant differences were most frequently noted for the more recent past (older adulthood) in cases, with more frequent consumption being recalled in the first questionnaire for all food items except carrots and broccoli. Perhaps this reflects the effect of current diet in recalling eating patterns for the more recent past, because cases are more likely to have altered their diets (by reducing fat intake and increasing vegetable consumption) as a consequence of their disease and its treatment. Citrus fruit was the only food item with highly significant trend differences across all four age periods in both cases and controls. Table 3 lists the weighted K-values for specific food items, comparing responses on the first (1980-1982) and second (1986-19H7) questionnaires. Food items with significant trend differences in response between the two questionnaires were not examined. In general, the K-statistics were similar for cases and controls and were consistent across the different age periods. The recall of frequency of consumption for the past was to some extent influenced by changes in recent consumption patterns for both cases and controls. Table 4 shows the correlation coefficients for the food items and age periods in which change in recent consumption had a significant influence on the recalled consumption for the distant past,
Vol. 13, No. 4
225
Table 2. Significant Trend Differences in the Response to Specific Food Items Between the 1980-1982 and 1986-1987 Questionnaires" Age Period
Downloaded by [New York University] at 08:47 10 February 2015
Cases Childhood
Food Item
No. of Pairs Examined
P Value (Two-Tailed)
Lettuce Spinach Other green vegetables Citrus fruit
185
< 0.001 0.002 < 0.001
