Increasing Fruit and Vegetable Consumption among Callers to the CIS: Results from a Randomized Trial

27, S16–S28 (1998) PM980405

PREVENTIVE MEDICINE ARTICLE NO.

Increasing Fruit and Vegetable Consumption among Callers to the CIS: Results from a Randomized Trial1 Alfred C. Marcus, Ph.D.,*,2 Jerianne Heimendinger, Sc.D.,* Pam Wolfe, M.S.,* Barbara K. Rimer, Dr.P.H.,† Marion Morra, M.A.,‡ Donna Cox, M.Ed.,§ Paula J. Lang, B.S.,¶ William Stengle, M.P.H.,| Marie Paule Van Herle, M.A.,** Doug Wagner, M.S.W., LCSW,†† Diane Fairclough, Dr.P.H.,* and Lynn Hamilton, B.A.‡‡ *AMC Cancer Research Center, Denver, Colorado 80214; †Duke Comprehensive Cancer Center, Durham, North Carolina 27705 and Division of Cancer Control and Population Science, National Cancer Institute, Bethesda, Maryland 20892; ‡ Morra Communications, Inc., Milford, Connecticut 06460; §Johns Hopkins Cancer Information Service, Baltimore, Maryland 212052004; ¶Cancer Information Service, University of Kansas Medical Center, Kansas City, Kansas 66160-7312; |Cancer Information Service, Karmanos Cancer Institute, Detroit, Michigan 48201; **Cancer Information Service, Jonsson Comprehensive Cancer Center/ UCLA, Los Angeles, California 90025-3511; ††Kentucky Cancer Information Service, Lexington, Kentucky 40536-0098; and ‡‡ Survey Research Laboratory, University of Illinois at Chicago, Chicago, Illinois 60607

Background. Results are reported from a large randomized trial designed to increase fruit and vegetable consumption among callers to the Cancer Information Service (CIS). Methods. CIS callers assigned to the intervention group received a brief proactive educational intervention over the telephone at the end of usual service, with two follow-up mailouts. Key educational messages and print material derived from the NCI 5 A Day for Better Health program were provided to intervention subjects. Subjects were interviewed by telephone at both 4-week (n 5 1,672) and 4-month (n 5 1,286) follow-up. Results. A single-item measure of fruit and vegetable consumption revealed a significant intervention effect of approximately 0.65 servings per day at 4-week follow-up (P , 0.001) and 0.41 servings per day at 4-month follow-up (P , 0.001). Using a seven-item food frequency measure that was also included in the 4-month interviews, a similar intervention effect of 0.34 servings per day was obtained (P 5 0.006). The vast majority of CIS callers (88%) endorsed the strategy of providing 5 A Day information proactively. Conclusions. A brief educational intervention delivered to CIS callers at the end of usual service was associated with an increase in self-reported fruit and vegetable intake. q1998 American Health Foundation and Academic Press

1 The research reported herein was supported by Grant P01CA57586, awarded by the NCI to Dr. Alfred C. Marcus, Principal Investigator. The views and conclusions expressed herein do not necessarily reflect those of the NCI. 2 To whom reprint requests should be addressed at the AMC Cancer Research Center, 1600 Pierce Street, Denver, Colorado 80214.

Key Words: cancer/prevention and control; diet; telephone information services; health education.

INTRODUCTION

The Cancer Information Service (CIS) was established in 1975 by the National Cancer Institute (NCI) to provide accurate, up-to-date information about cancer to cancer patients, relatives and friends of cancer patients, health professionals, and the general public [1]. To fulfill this critically important mandate to the nation, the CIS currently maintains 19 regional offices nationwide. All regional offices provide a telephone information service that can be accessed by calling a tollfree telephone number (1-800-4-CANCER). There are over 500,000 calls per year. In addition, the CIS also conducts outreach activities to disseminate information about cancer to the medically underserved, including minority groups and people with limited access to health information and services. The Cancer Information Service Research Consortium (CISRC) was initiated in 1993 to conduct policyrelevant intervention research within the CIS [2]. In this study, an educational intervention to increase fruit and vegetable consumption was tested among callers to the CIS. Several factors contributed to the decision to focus on fruit and vegetable consumption. Foremost was epidemiological evidence suggesting that as many as 35% of all cancer deaths can be attributed to dietary factors [3,4], and of all dietary factors hypothesized to affect cancer, the epidemiologic evidence was strongest for the protective effects of fruit and vegetable consumption [5–7]. In addition, evidence also suggests that about

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0091-7435/98 $25.00 Copyright q 1998 by American Health Foundation and Academic Press All rights of reproduction in any form reserved.

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60–70% of the adult U.S. population eat fewer than five servings of fruits and vegetables per day [8,9], which is the minimum daily consumption recommended by the U.S. Department of Agriculture, the U.S. Department of Health and Human Services, and the National Academy of Sciences [10–12]. A final consideration to focus the study on fruit and vegetable consumption was the ongoing participation of the CIS in the NCI 5 A Day for Better Health program [13–15]. As a valued partner in the 5 A Day program, the CIS routinely responds to specific requests for 5 A Day information. In contrast to this approach, the study reported herein tested a different intervention strategy in which the CIS provided 5 A Day information proactively to CIS callers (i.e., at the end of usual service, CIS Information Specialists provided 5 A Day educational messages to callers who did not specifically request such information as their reason for calling the CIS). In an earlier pilot study, this intervention was shown to be both feasible and potentially efficacious in promoting increased fruit and vegetable consumption among CIS callers [16]. However, this pilot study was limited to a relatively short follow-up period for outcome evaluation (4 weeks). The study reported herein addresses this limitation by extending the follow-up period to 4 months. RESEARCH METHODS

Overview of Research Design As shown in Fig. 1, the 5 A Day intervention was tested using a randomized two-group design. Eligible CIS callers were randomized within CIS offices based on the day of the week they called the CIS (10 days were devoted to accrual), with the constraint that the design be balanced. That is, our goal was to accrue approximately the same number of subjects in each study condition. The pattern for alternating intervention and control over the 10-day accrual period, with a 50% chance of starting with control, was assigned to the offices by the research team before the study began. One office was unable to begin accrual on the designated start date and thus had a total of 5 intervention days and 4 control days. Callers were considered eligible for this study if they met all of the following criteria: (1) no information was provided to the caller about diet and nutrition as part of usual service (thus allowing for this information to be provided proactively), (2) the caller was not a cancer patient in treatment or awaiting treatment (delivering the nutritional message to such callers was considered inappropriate), (3) the caller was not on a prescribed diet that would limit fruit and vegetable consumption, (4) the caller could receive the intervention in English, (5) the caller was not significantly distressed at the time of the call (as determined by the Information Specialist), (6) the subject had not called

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the CIS previously during the study accrual period, (7) the caller was at least 18 years of age, and (8) the caller consented to a brief interview appended to usual service, as well as two telephone interviews that would be completed at 4-week and 4-month follow-up. All callers who satisfied the above eligibility criteria (both intervention and control) were then interviewed by the CIS Information Specialist at the end of usual service. This baseline interview: (1) defined a serving size (i.e., “. . .a serving is about a medium-sized apple or –21 cup of chopped vegetables or fruit or about 6 oz of 100% fruit or vegetable juice.”), (2) asked about current fruit and vegetable consumption (“About how many servings of fruits and vegetables do you usually eat or drink on an average day? Please include fruits, vegetables, and 100% fruit or vegetable juices in your number.”), and (3) asked about future intent (“In the future, do you think you will be eating more, less, or about the same number of servings of fruits and vegetables as you do now?”). The consumption question was based on two summary questions used in the Block food frequency questionnaire [17]. The Survey Research Laboratory at the University of Illinois (Chicago) tested the single-item question vs the Block two-item question and found the two versions to be similar in reports of fruit and vegetable consumption [16]. Thus, the one-item question, which took about 45 s less than the two-item measure, was selected in order to keep the total intervention time within the 6-min limit that was recommended by CIS staff. Also included in the baseline interview were selected demographic questions (e.g., gender, education, race/ethnicity, income) as well as questions obtaining the name, telephone number, and address of the caller (to be used for the follow-up telephone interview). In addition to the above, callers assigned to the intervention received a somewhat longer version of the baseline interview, along with two follow-up mailouts. The proactive educational intervention was embedded within this longer baseline interview (to be described below). Both groups of callers were then interviewed by telephone at 4-week and 4-month follow-up to assess the short-term effects of the proactive 5 A Day intervention. Description of Intervention The intervention tested in this study utilized stagedbased messages and specific behavioral suggestions that were conveyed to callers by CIS Information Specialists at the end of usual service, as well as two followup mailouts to reinforce the key intervention message to eat at least five servings of fruits and vegetables per day. Several theoretical models informed the development of this intervention. The Transtheoretical Model [18,19] guided the development of messages that were tailored to the subject’s self-reported baseline consumption and future intentions regarding fruit and vegetable

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FIG. 1. Overview of research design.

intake. The Theory of Reasoned Action [20] with its focus on behavioral intentions as a marker of behavior change, is also clearly evident in the intervention. In addition, many of the specific behavioral suggestions conveyed to intervention subjects anticipate barriers that can be inferred from the Health Belief Model [21,22], while the reinforcement mailings are consistent with behavior change principles derived from Social Cognitive Theory [23,24]. Following the baseline assessment, the Information Specialist provided intervention subjects with a short

series of targeted messages. If the caller was not thinking about eating more fruits and vegetables, motivational messages were read or paraphrased to the caller (e.g., “Research has shown that eating more fruits and vegetables may reduce your chances of developing certain kinds of cancer and heart disease; we’d like to suggest that you try to gradually increase the amount of fruits and vegetables to at least five servings each day.”). If the caller indicated that he/she was thinking about eating more fruits and vegetables, this response was reinforced by the Information Specialist (e.g.,

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“That’s great that you’re thinking of eating more fruits and vegetables. Research has shown that eating more fruits and vegetables may reduce your chances of developing certain kinds of cancer and heart disease; the goal is to try to eat at least five servings each day.”). All callers assigned to the intervention condition then received a short list of concrete behavioral suggestions for increasing fruit and vegetable consumption. These suggestions included the following: • At breakfast, have a glass of juice. • At lunch, eat cut up fruit and vegetables as munchies instead of chips. • At dinner, add raw vegetables to your salad. • For snacks, keep a bowl of fruit out on the kitchen counter. • When eating out, choose restaurants that offer a salad bar. In the final segment of the telephone portion of the intervention, Information Specialists asked callers if they would try to eat more fruits and vegetables: “Given everything we’ve talked about, would you be willing to commit to eating at least one more serving of a fruit or vegetable each day?” Permission was then obtained to mail to the caller additional material related to fruit and vegetable consumption. The intervention interview concluded with a short list of demographic questions identical to those asked of callers in the control condition (i.e., gender, education, race/ethnicity, income), as well as a brief summary of the information that was conveyed to the caller as part of the intervention. Immediately following the intervention interview, CIS Information Specialists mailed the first of two packets of materials to the caller. If the caller reported eating fewer than five servings per day at baseline, the first mailing included Take Five: A Guide to Healthful Eating, a booklet developed at the Fred Hutchinson Cancer Research Center as part of their NCI 5 A Day research project [25]. This booklet contained suggestions, worksheets, and recipes to help increase fruit and vegetable consumption. If, on the other hand, the caller reported eating five or more servings per day at baseline, the first mailing included a slightly modified version of this booklet that did not specifically focus on eating five servings per day, but instead focused on increasing fruit and vegetable intake (Reach Your Peak with Produce: A Guide to Healthful Eating). Also included in the first mailing was a 5 A Day brochure, Eat More Fruits and Vegetables; a bookmark/tip card, Eat More Salads; and a 5 A Day magnet. The second packet, which was mailed about 14 days later, was prepared and mailed centrally by research staff located at the AMC Cancer Research Center in Denver, Colorado. Items in this second mailout included a recipe book entitled Tastes for All Seasons: Ripe and Ready Recipes, two 5 A Day brochures (Time to Take Five: Eat 5 Fruits

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and Vegetables a Day, Five a Day for Better Health), and a magnet and pencil with the 5 A Day logo. Both mailouts were accompanied by one of three cover letters tailored to the caller’s response to the consumption and future intent questions. Training Program and Subject Accrual Six of the 19 CIS offices participated in the 5 A Day study. These offices were located in New Haven, Connecticut (Region 1, serving the New England states); Baltimore, Maryland (Region 5, serving the District of Columbia, Maryland, and Northern Virginia); Lexington, Kentucky (Region 9, serving Arkansas, Kentucky, and Tennessee); Detroit, Michigan (Region 12, serving Indiana and Michigan); Kansas City, Kansas (Region 13, serving Illinois, Kansas, Missouri, and Nebraska); and Los Angeles, California (Region 18, serving Southern California). Consistent with the overall training philosophy of the CIS, a 2-day train-the-trainers program was used to prepare offices for the main study. Thus, CIS Telephone Service Managers were initially trained at a centralized location, and then they conducted their own training program on-site using materials and a training manual prepared by the research team. Once fieldwork began, Telephone Service Managers monitored telephone calls for adherence to protocol. Implementation of the intervention was further enhanced via regularly scheduled conference calls with the research team. Prior to study implementation, each office was supplied with all forms and mailout materials necessary to conduct the study, which occurred between September 5 and September 20, 1995. During this 16-day period (of which 10 were devoted to accrual), a total of 2,126 eligible callers were enrolled. The refusal rate by eligible CIS callers at the time of enrollment was less than 5%. Telephone Follow-up Interviews The telephone follow-up interviews averaged less than 20 min. To provide a segue into the interview of CIS callers, the 4-week interview began with a short series of questions to assess caller satisfaction with the CIS (e.g., “Was the information you received from the CIS helpful?”, “Was your most important question answered by the CIS?”, “How would you rate your overall satisfaction with the CIS?”). Then, questions were asked about current consumption of fruits and vegetables and future intent (i.e., callers were once again asked the two questions described earlier), knowledge of the 5 A Day recommendation for daily consumption of fruits and vegetables, and the subject’s ability to correctly identify the national 5 A Day program. Also included were 15 Likert-type questions designed to assess predisposing and enabling psychosocial factors pertaining to fruit and vegetable consumption. Several

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of these latter questions were adapted from previous diet and nutrition surveys, including the NCI-funded Working Well Trial [26,27]. The specific wording of these 15-Likert-type questions has been reported elsewhere [16]. Callers were then asked several questions to determine the usefulness of the 5 A Day print material provided as part of the intervention (e.g., “Did you do any of the exercises from the booklet or brochures?”, “Did you use any of the recipes in the materials?”, “Did you use any of the tips in the material on how to eat more fruits and vegetables?”—If yes, “which ones?”). A final question asked the caller to evaluate the appropriateness of using the CIS to provide proactive education and counseling. The 4-month interviews were similar to the 4-week interviews. However, to reduce respondent burden, the 15 psychosocial items were not repeated at 4-month follow-up nor were the questions pertaining to use of the print material. In addition, at 4-month follow-up callers were asked a seven-item food frequency questionnaire that was used as an outcome measure in previous research of the 5 A Day program [13–15]. The questionnaire is patterned after a similar measure used by the Centers for Disease Control in their Behavioral Risk Factor Surveillance Survey and subsequently validated by Serdula et al. [28]. This index asked callers to indicate how frequently they eat or drink the following (i.e., number of times per day, week, or month): 100% orange juice or grapefruit juice; other 100% fruit juices; green salad; french fries or fried potatoes; baked, boiled, or mashed potatoes; vegetables (not counting salad or potatoes); and fruit (not counting juice). After omitting french fries and fried potatoes (this item was specifically included to identify and then omit french fries and fried potatoes from the measure of recommended fruit and vegetable intake), the answers to the six remaining questions were coded into a common metric and summed to form a composite measure of servings per day. The follow-up rate at 4 weeks was 78.6% (1,672/2,126). Four-month follow-up interviews were only attempted on those subjects successfully interviewed at 4-week follow-up, with a follow-up rate of 76.9% among those interviewed at 4 weeks (1,286/ 1,672), or 60.5% among those interviewed at baseline. There were no differences in follow-up rates by intervention condition at 4 weeks (intervention 78.7%; control 78.6%). However, at 4-month follow-up, control subjects were somewhat more likely to be interviewed than intervention subjects (63.2% vs 57.7%). Statistical Analyses Comparisons of demographic characteristics and baseline measures of fruit and vegetable consumption among callers assigned to the intervention and control groups were performed using the Pearson’s x2 statistic

for unordered categorical variables (i.e., race/ethnicity), the Mantel–Haenszel x2 statistic [29] for ordered categorical variables (i.e., education), and the Kolmogorov– Smirnov test [30] for the maximum deviation between two empirical distributions for baseline fruit and vegetable consumption. The same tests were used to compare individuals who completed the 4-month followup interview with those who were lost to follow-up. Comparisons of the 15 Likert-type psychosocial questions were made using the Mantel–Haenszel x2 statistic for ordered categorical variables [29]. In all of the above analyses, significance levels were adjusted for multiple comparisons using a Bonferroni correction. Maximum likelihood estimates of a multivariate (repeated measures) model using all available data were used for the analysis of the primary endpoints (i.e., selfreported fruit and vegetable consumption at both 4week and 4-month follow-up [31]). This approach is conceptually identical to multivariate analysis of variance but avoids case-wise deletion of subjects with missing assessments. This approach relaxes the restrictive assumption that the data are missing completely at random and provides unbiased estimates under the less restrictive assumption of missing at random [32]. Given that subjects were randomized by day within site, we tested for the presence of clustering of responses within the unit of randomization (day within site) and found no evidence of correlation among callers. RESULTS

Description of Sample Previous research has shown that callers to the CIS tend to be female, non-Hispanic white, and of higher socioeconomic status [33]. Data reported in Table 1 confirm this sociodemographic profile for the 5 A Day study. As shown, 80% of callers enrolled in the 5 A Day study were female, about 75% reported at least some college (nearly 50% were college graduates or reported postgraduate education), 45% reported family incomes of $50,000 or greater, and over 85% of the sample were non-Hispanic whites. About 50% of the sample was between 30 and 49 years of age, while slightly more than 20% of the sample was 60 years of age or older. Of the total enrolled sample at baseline, there was modest variability across CIS offices in accrual, ranging from a high of 22% of the sample enrolled by CIS Region 13 to a low of about 14% for CIS Region 9. Approximately 70% of the baseline sample reported eating fewer than five servings of fruit and vegetables per day, while nearly 50% reported an intention to eat more servings of fruit and vegetables. Table 1 also reports the baseline characteristics of the subsample (n 5 1,286) successfully interviewed at both 4-week and 4-month follow-up. As indicated, the

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TABLE 1 Comparison of Sample Enrolled at Baseline with Sample Completing Telephone Follow-up Interviews Sample enrolled at baseline Characteristics Gender Female Male Age ,30 years 30–39 years 40–49 years 50–59 years 60–69 years 701 years Education Some high school High school graduate Some college College graduate Postgraduate Income Less than $20,000 $20,000–$29,999 $30,000–$39,999 $40,000–$49,999 $50,000–$59,999 $60,0001 Race/ethnicity Black Hispanic White Other Fruits and vegetables: Baseline consumption 0–3 servings per day 4 servings per day 5 servings per day 6 servings per day 7 or more servings per day Fruits and vegetables: Baseline intentions Eat more servings per day Eat same number of servings per day Eat fewer servings per day CIS Office 01 New Haven, CT 05 Baltimore, MD 09 Lexington, KY 12 Detroit, MI 13 Kansas City, KS 18 Los Angeles, CA

Sample completing telephone interviews at 4-week and 4-month follow-up n

%

P valuea

80.0 20.0

1,046 229

82.0 18.0

0.032

246 472 565 361 303 164

11.6 22.4 26.8 17.1 14.3 7.8

117 277 360 232 190 102

9.1 21.7 28.2 18.1 14.9 8.0

92 416 599 566 443

4.3 19.7 28.3 26.7 20.9

55 264 382 327 254

4.3 20.6 29.8 25.5 19.8

268 357 249 204 266 611

13.7 18.3 12.7 10.4 13.6 31.3

155 218 169 128 167 353

13.0 18.3 14.2 10.8 14.0 29.7

130 49 1,821 111

6.2 2.3 86.3 5.3

77 28 1,104 71

6.0 2.2 86.2 5.6

1,064 401 300 156 197

50.2 18.9 14.2 7.4 9.3

630 252 193 91 117

49.1 19.6 15.0 7.1 9.1

NS

991 1,013 29

48.7 49.8 1.4

608 616 13

49.1 49.8 1.0

NS

324 341 293 308 469 391

15.2 16.0 13.8 14.5 22.1 18.4

194 195 183 206 277 231

15.1 15.2 14.2 16.0 21.5 18.0

n

%

1,688 421

0.008

NS

NS

NS

NS

a

P values correspond to the comparison of callers who completed the 4-month interview (second columm) with those who were lost to follow-up (first column minus second columm). All P values reported were adjusted using the Bonferroni correction. For gender, race, and CIS office, P values are for the Pearson’s x2 statistic. For the ordered categories of age, education, income, and intentions, P values are based on the Mantel–Haenszel x2 statistic. For baseline consumption of fruits and vegetables, P values are based on the Kolmogorov–Smirnov test on the maximum deviation between two empirical distributions.

sample of callers successfully interviewed at both follow-up points was, for the most part, highly representative of the sample enrolled at baseline. When significant differences were found (i.e., gender, age), the

magnitude of these differences was quite small. Additional analyses were conducted to determine whether the intervention and control groups were comparable at baseline on the measures reported in Table 1. In all

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cases, there were no significant differences between groups at baseline. Implementation Evaluation Several key indicators pertaining to implementation evaluation were assessed, including adherence to the eligibility criteria and randomization protocol of the study. Based on a review of the baseline interviews, adherence to both of these protocols by CIS Information Specialists was 99%. In addition, during the 4-week follow-up interviews, intervention subjects were asked whether the Information Specialists talked with them about eating more fruits and vegetables. Of the 838 intervention subjects who were successfully interviewed at 4-week follow-up, 98% reported that the Information Specialists did in fact talk with them about eating more fruits and vegetables. When asked if any of the information that was provided by the CIS (with respect to fruit and vegetable consumption) was new to them, 40% of intervention subjects answered yes and 59% answered no (the remainder could not recall). The educational component of the intervention that was delivered over the telephone was designed to take about 6 min. This time limit was critial in order to minimize disruption of normal CIS service (i.e., during implementation of the intervention Information Specialists also had to maintain their regular service to CIS callers). Thus, it is important to note that the length of time on the telephone averaged 5.8 min for intervention subjects, compared with 3.6 min for control subjects. Several questions were asked at 4-week follow-up regarding the intervention materials. Nearly all intervention subjects (98%) reported receiving the intervention materials. However, only about 40–50% of intervention subjects were able to identify the specific materials they received, including the magnet (39%), the main intervention booklet Take Five: A Guide to Healthful Eating or Reach Your Peak with Produce: A Guide to Healthful Eating (47%), the supplemental recipe book Tastes for All Seasons (52%), or any of the 5 A Day brochures that were mailed (55%). Very few intervention subjects (approximately 5%) reported receiving the bookmark Eat More Salads. When asked how much of the material they had read, about 50% of intervention subjects answered a lot, another 26% answered some, 12% answered little or none, while the remainder could not recall how much they had read. Another series of questions asked intervention subjects which specific components of the materials they actually used. Approximately half of intervention subjects who reported receiving material said they used the tips or suggestions included in the material (48%), only 13% reported using the recipes, and an even smaller percentage (5%) reported using the worksheets.

Of special note is that 52% of intervention subjects who reported receiving material indicated that they shared this material with someone else, including other family members (41%), friends (9%), and neighbors and coworkers (6%). Finally, all subjects (both intervention and control) were asked whether they thought CIS Information Specialists should provide information about fruit and vegetable consumption to callers, even if that was not their reason for calling the CIS. The vast majority of subjects endorsed this strategy (88%). Intervention subjects were significantly more likely to endorse this proactive strategy than control subjects (92% vs 84%, P 5 0.001). Outcome Evaluation As noted earlier, during the 4-week follow-up interviews subjects were asked a series of 15 Likert-type questions to assess predisposing and enabling psychosocial factors related to fruit and vegetable consumption. One of the main research hypotheses is that intervention subjects will be more likely to endorse these psychosocial factors than control subjects. To test this hypothesis, factor analyses were conducted to create a composite index of these items. Exploratory analyses indicated that a one-factor solution was optimal, with a resulting a coefficient of 0.69. When these items were summed to create a composite index (after reverse coding those items that were worded in the opposite direction), there was no significant difference in mean scores between the two groups. Similarly, an item-byitem analysis indicated that 13 of the 15 questions also showed no difference between groups. Of the 2 questions showing a significant difference, the magnitude of these differences was modest. Thus, 43.7% of intervention subjects agreed strongly that “Eating a lot of fruits and vegetables decreases my chances of getting serious diseases like cancer or heart disease,” compared with 36.6% for control subjects (P , 0.001). With respect to the item “I have a lot of information on how to eat in a healthy way,” 92.4% of intervention subjects were in agreement (i.e., strongly agree or agree), compared with 86.0% for control subjects (P , 0.002). Knowledge of the 5 A Day program was also assessed at 4-week follow-up. As expected, the intervention group was much more likely than the control group to identify five or more servings per day as the recommended guideline for fruit and vegetable consumption (81% vs 65%, P 5 0.003). Another question, asked at both 4-week and 4-month follow-up, was whether the subject tried to eat more fruits and vegetables. For this item there were also significant differences in the predicted direction. Among intervention subjects at 4-week follow-up, 82% reported that they tried to eat more fruits and vegetables, compared with 56% for control subjects (P ,

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0.001). At 4-month follow-up, a similar difference was obtained (intervention 80%, control 64%, P , 0.001). The primary endpoint for evaluating the efficacy of the proactive educational intervention is self-reported fruit and vegetable consumption. As indicated in Table 2, there was no significant difference between groups in self-reported fruit and vegetable consumption at baseline. However, at 4-week follow-up there was a significant difference (single-item measure), with intervention subjects reporting 0.65 more servings of fruits and vegetables per day than control subjects (P , 0.001). At 4-month follow-up, intervention subjects continued to report more servings per day than control subjects (0.41 servings, P , 0.001). In addition, a significant intervention effect was also found using the sevenitem measure, with intervention subjects reporting 0.34 more servings per day than control subjects (P 5 0.006). Also evident from Table 2 is a reduction in group differences between 4-week and 4-month follow-up (single item). There was a significant but small increase in fruit and vegetable consumption between 4-week and 4-month follow-up in the control group (x change 5 3.93 2 3.79 5 0.14 servings; 95% CI 0.01, 0.25). In contrast, for the intervention group there was a small decrease in consumption between 4-week and 4-month followup (x change 5 4.34 2 4.44 5 20.10 servings; 95% CI 20.22, 0.02). This differential pattern of change resulted in significant attenuation of group differences between 4-week and 4-month follow-up (i.e., change in group differences 5 20.24 servings; 95% CI 20.41, 20.07, P 5 0.006). However, as noted above, despite this attenuation group differences remained statistically significant at 4-month follow-up (0.41 servings per day, P , 0.001). The data reported in Fig. 2 allow for a more detailed look at group changes over time. As indicated, the overall distribution of fruit and vegetable consumption at baseline (single item) was highly comparable for both groups. However, at both 4-week and 4-month followup, we observe a noteworthy shift in the entire distribution of fruit and vegetable consumption for the intervention group, which is much less apparent in the control group.

In addition to the significant intervention effects noted above, other potential predictors of fruit and vegetable consumption at both 4-week and 4-month followup were examined, including age, gender, and education. Results indicated that younger age, male gender, and less education were associated with reported consumption of fewer servings of fruits and vegetables (P , 0.05). However, none of these characteristics interacted statistically with the impact of the intervention (P $ 0.20) nor did baseline intentions to eat more fruits and vegetables. DISCUSSION

Baseline estimates of fruit and vegetable consumption indicate that a sizeable majority of CIS callers (approximately 70%) report eating fewer than five servings of fruits and vegetables per day. This estimate is consistent with national estimates for the U.S. adult population [8,9]. Also consistent with previous research were the demographic predictors of fruit and vegetable consumption found in this study (i.e., age, gender, and education). For example, Glanz and colleagues found in the Working Well study that females, older respondents, and those with more education were more likely to be in later stages of change and to consume more fruits and vegetables and less fat [34]. These same associations have been found in other studies, including the national 5 A Day for Better Health baseline survey [9,35–37]. In the 5 A Day survey, women had higher intakes of fruits and vegetables than men at all ages, and intakes increased with education and income. Also evident from this study were high levels of adherence to protocol by CIS Information Specialists, including adherence to the eligibility criteria and randomization protocol and reports by intervention subjects that they did in fact receive the telephone counseling component of the educational intervention. Although nearly all intervention subjects reported receiving material in the mail, their recall of specific intervention materials was much lower (approximately 40–50% for the main intervention materials that were mailed), as was their reported use of these materials (e.g., tips on

TABLE 2 Multivariate Analyses of Self-Reported Fruit and Vegetable Consumption by Intervention–Control Group Time

Items

Group

Baseline

1

4 week

1

4 month

1

4 month

7

Intervention Control Intervention Control Intervention Control Intervention Control

N 1,054 1,064 821 818 609 668 615 671

Mean

Std

Difference

P value

3.78 3.73 4.44 3.79 4.34 3.93 4.83 4.50

2.11

0.04

0.65

2.07

0.65

,0.001

2.05

0.41

,0.001

2.27

0.34

0.006

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FIG. 2. Distribution of fruit and vegetable consumption at baseline and at 4-week and 4-month follow-up by intervention–control group (single item).

how to increase fruit and vegetable consumption, 48%; recipes, 13%; worksheets, 5%). Nearly 90% of CIS callers endorsed the concept of providing 5 A Day information proactively to CIS callers. This same finding was reported in the pilot study [16], as well as in an earlier study testing a proactive educational intervention to promote screening mammography among CIS callers [38]. Results obtained from both follow-up assessments suggest an intervention effect that diminishes over time

but remains statistically significant. Using the singleitem measure of fruit and vegetable consumption, the intervention group reported 0.65 more servings per day than the control group (P , 0.001), compared with 0.41 servings per day (P , 0.001) at 4-month follow-up. As in the case of the single-item indicator, a significant intervention effect was also obtained at 4-month followup using the seven-item food frequency measure, with a group difference of 0.34 servings per day (P 5 0.006).

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Additional analyses suggest two mediating processes responsible for the significant intervention effect. One such factor was the success of the intervention in improving knowledge of the 5 A Day guidelines for fruit and vegetable consumption. Intervention subjects were more likely to correctly identify the 5 A Day guidelines than control subjects (81% vs 65%, P 5 0.003). Also striking were differences between groups in their selfreported attempts to increase fruit and vegetable consumption. At baseline, approximately 50% of both groups reported that they planned to eat more fruits and vegetables. However, at 4-week follow-up, 82% of the intervention group reported that they tried to increase their consumption of fruits and vegetables compared with 56% of the control group (P , 0.001). Similar differences were also reported at 4-month follow-up (intervention 80%, control 64%, P , 0.001). In contrast to the above, there were few differences between groups at 4-week follow-up in their responses to the predisposing and enabling psychosocial factors assessed in this study. It is unclear exactly why the predisposing and enabling factors do not appear to function as mediating variables. Perhaps among this highly educated group of information seekers (i.e., CIS callers) who may already be sensitized to the threat of cancer, simply clarifying and reinforcing what the NCI recommends is a sufficient cue to action. In any event, it is unlikely that this finding of no difference is a random occurrence or a Type II error, because results from our pilot study support this same basic conclusion [16]. Although estimates of group differences ranging from 0.34 to 0.41 servings per day (at 4-month follow-up) compare favorably to previous intervention studies [37,39], a key question is whether this intervention effect is clinically significant. Even small increases in fruit and vegetable consumption appear to have a protective effect against cancer [5–7,40–45]. However, the definitive answer to this question is not yet known. This underscores the need for additional research to more precisely characterize the protective effects of fruit and vegetable consumption, as well as to maximize the effects of behavioral interventions designed to promote healthy dietary practices [46]. Another key issue that arises in all self-report measures of fruit and vegetable consumption is the extent to which these self reports are providing reliable and valid estimates of fruit and vegetable consumption. Random measurement error in the outcome measure will increase the variance, thus making it more difficult to show a significant intervention effect. Despite this possibility, the intervention effects remained statistically significant at both 4-week and 4-month followup. If there were systematic errors that affected both groups in the same way, this should have little or no effect on the relative comparisons between groups. In

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contrast, measurement error that differentially affects the reporting behavior of intervention and control subjects would be cause for great concern. There would seem to be two main sources of differential reporting error that need to be considered when evaluating the results of this trial. The first source of measurement error occurs if the intervention group received more information about the correct definition of a serving size, which might then produce higher reporting levels in the intervention group (e.g., if subjects initially overestimate what constitutes a serving size, correct knowledge of a serving size could increase the number of servings reported by subjects). Although the intervention group did receive more of this information than the control group via the intervention print material, intervention subjects did not report extensive use of these materials. More important, however, is the fact that guidelines for defining a serving size were provided to both intervention and control subjects as part of the fruit and vegetable assessments (i.e., parameters defining a serving size were included in the introduction to the fruit and vegetable intake questions). The second source of differential reporting error would occur if intervention subjects were more likely than control subjects to give socially desirable answers. According to this argument, intervention subjects will report higher consumption of fruits and vegetables than control subjects because they believe this is what the interviewer wants to hear. Clearly, this alternative interpretation needs to be acknowledged, and several collateral findings may help evaluate the plausibility of this rival hypothesis. For example, as noted above, the effects of the intervention diminished between 4-week and 4-month follow-up, which is probably not a sufficient amount of time to reduce social desirability, but is sufficient to show attenuation or relapse in behavior change. In addition, intervention subjects did not report extensive use of the intervention materials (e.g., recipes, tips, worksheets), which would be expected if social desirability were a significant source of reporting bias. A similar argument can be made for the lack of difference found between intervention and control subjects in most of the attitude and belief items assessed at 4week follow-up. Also noteworthy is that the distribution of fruit and vegetable consumption, at both 4-week and 4-month follow-up, did not reveal a large singular spike at five servings per day for intervention subjects (see Fig. 2). If social desirability were a major source of measurement error, one would expect to see such a spike among intervention subjects at precisely this point in the distribution (i.e., because “5 a day” is the socially desirable answer). Similarly, if an intervention by social desirability interaction were a major source of measurement error, one would expect large reporting differences between groups at precisely this point in the distribution

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of fruit and vegetable consumption. However, a review of Fig. 2 indicates that while intervention subjects were more likely than control subjects to report five servings per day, these differences were not large. One intriguing finding from this study has to do with the different estimates of fruit and vegetable consumption recorded by the single-item measure vs the sevenitem measure at 4-month follow-up (the estimate derived from the seven-item measure was approximately 0.5 servings higher than the single-item measure). The Pearson correlation coefficient between the seven-item and the single-item measures was 0.53 (P 5 0.0001; n 5 1,277). This compares favorably to correlations found in other studies between food records, food frequencies, and short screeners [28,47]. The higher reporting levels found with the seven-item measure may be explained in part by the greater number of opportunities to report fruit and vegetable consumption (seven specific categories of response) vs the single-item global measure. In addition, the seven-item measure does not specifically assess serving size and hence partial servings will be captured with the seven-item measure (the single-item measure specifically defined a serving size in the question stem). Finally, the seven-item measure allows for responses in terms of days, weeks, and months, which provides subjects with the opportunity to report consumption patterns that are less frequent than daily, while the single item measure specifically requested number of fruit and vegetable servings “on an average day.” This latter difference between the two measures also allows the seven-item measure to record partial servings when the data are converted into a common metric of “servings per day” (e.g., four salads per month 5 0.133 salads per day). All of these differences make a direct comparison of the seven-item and single-item measures problematic. Nonetheless, despite these differences, the intervention effect was robust across both measures of fruit and vegetable consumption. Moreover, it is the relative difference between the two experimental groups that is the key outcome criterion, and the two measures were highly consistent in this regard (difference between groups at 4-month follow-up: single item 0.41; seven item 0.34, or a difference of group differences of only 0.07 servings per day). CONCLUSIONS

There is a growing body of research documenting the efficacy of cancer control interventions delivered over the telephone. This research has shown that telephonebased interventions can facilitate smoking cessation [48] and improve rates of cancer screening and followup [37,49–53]. To this list we can now add fruit and vegetable consumption. Results from this study suggest

a significant intervention effect at both 4-week and 4month follow-up. Moreover, based on a review of several collateral findings from this study, it would appear that the observed differences between groups cannot be adequately explained by several key rival hypotheses, including social desirability. Taken together, these findings argue in favor of a significant intervention effect that was replicated in both a single-item measure and a previously validated seven-item measure of fruit and vegetable intake. The study reported herein also suggests several profitable directions for future research. One such recommendation would be to incorporate other endpoints (in addition to self-report) into the outcome evaluations of behavioral interventions to increase fruit and vegetable consumption. Self-report measures, no matter how well conceived, will be susceptible to criticisms of reporting bias. Thus, if biological or biochemical endpoints can be used to supplement self-report, then the overall integrity of the research would be strengthened. Clearly, this recommendation would be difficult to implement in large geographically dispersed trials, although collecting appropriate specimens (e.g., blood, urine) on a random subsample of subjects might be feasible. The major challenge is to identify biomarkers that would be economical to analyze and would have acceptable levels of sensitivity and specificity to changes in fruit and vegetable consumption. A few candidate measures suggested by other studies are the plasma carotenoids, a-carotene, b-carotene, b-cryptoxanthin, and lutein [54–56]. However, more research is needed before these measures could be recommended for widespread use in behavioral intervention trials of fruit and vegetable consumption. Another recommendation for future research involves the length of time devoted to follow-up. Although the main study, in contrast to the previously reported pilot study, extended the follow-up period to 4 months, it still remains to be seen whether a significant intervention effect can be sustained longer term. Also worthy of additional research is the potential for secondary diffusion of this type of intervention. Although a high percentage of intervention subjects said they did not use specific components of the intervention materials, about 50% said they shared these materials with someone else. The extent to which these materials influence the dietary practices of the subject’s wider social network (including both the immediate family and beyond) would be important to document. Finally, another important direction for future research would be to test this or a similar intervention on underserved populations (e.g., low-income, low-literacy populations, racial/ethnic minorities). Callers to the CIS are not representative of the general population. However, a companion paper appearing in this issue of

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Preventive Medicine reports that a paid media campaign (radio and television) substantially increased call volume to the CIS from African American smokers [57], arguably one of the most difficult and challenging populations for the CIS to reach. Thus, the strategic use of mass media could extend the CIS telephone service to underserved populations, thereby allowing this intervention to be disseminated to other population subgroups. In addition, other organizations and agencies that provide services to low-income populations could adapt and test this intervention, especially if telephone contact is part of regular service (e.g., telephone reminders for appointments, telephone follow-up for missed appointments or to reinforce behavioral recommendations that were delivered in person). It is also conceivable that the telephone component of this intervention could be modified and delivered in person (in conjunction with follow-up print material). All of these possibilities await future research.

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ACKNOWLEDGMENTS The authors gratefully acknowledge the collaboration of the participating CIS offices and, in particular, the CIS Information Specialists who delivered the telephone intervention and the Telephone Service Managers who trained and supervised the Information Specialists. Special thanks are extended to Dr. Sherry Mills, Program Director, Division of Cancer Prevention and Control, for her unwavering support and assistance provided throughout this project. Special thanks are also extended to Ms. Chris Thomsen, Chief, Cancer Information Service Branch, NCI, for her substantial ongoing support for this program of research. A special acknowledgment is also due the Fred Hutchinson Cancer Center and, in particular, Drs. Shirley Beresford and Sue Curry for allowing us to distribute to intervention subjecfts the Take Five: A Guide to Healthful Eating booklet that was developed under a grant from the NCI (R01 CA5973). Finally, special thanks are extended to Ms. Mischelle Stricker and Ms. Tricia Leakey for assisting in project management.

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