Virtual Advisors for Physical Activity Promotion in Underserved Communities
Phase: NA
Conditions: Sedentary Lifestyle
Sponsor: Stanford University

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Study Protocol and Statistical Plan for  
Virtual Advisors for Physical Activity Promotion in Underserved Communities 
NCT02111213 
June 30, 2019 

 
 
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1. Introduction  
Physical inactivity is responsible for nearly 10% of major non-communicable 
diseases (NCDs) worldwide.1 In the U.S., population-level data suggest that increasing 
regular moderate physical activity could reduce annual medical costs by as much as 
$76.6 billion.2 While national guidelines for physical activity promotion emphasize the 
importance of appealing and convenient physical activities such as walking,3 a 
significant proportion of Americans (33%) remains inactive.4 This is particularly true for 
older (45% inactive), low-income (46% inactive), and Latino adults (44% inactive),4 who 
have high rates of obesity and other chronic conditions (e.g., Type 2 diabetes)5 in 
combination with often reduced access to programs to improve physical and mental 
health.6 
Few physical activity programs have taken into account the cultural preferences and 
needs of Latino Americans—among the fastest growing segments of the U.S. 
population, including aging adults.7 The major objective of the COMPASS Trial is to 
systematically compare culturally adapted and individually tailored physical activity 
counseling for midlife and older Latino adults delivered through two different 
communication channels: trained peer advisors (called promotores de salud) vs. a 
virtual advisor (i.e., a computer-based embodied conversational agent named 
“Carmen”). Peer or lay health advisors, which have been in existence in Latino 
communities for decades,8 are typically members of the community in which they work, 
sharing the community’s culture, language, and environment.9,10-12 However, few such 
programs have specifically targeted physical activity counseling.13 Similarly, while 
evidence suggests that aging adults as well as Latinos and other racial/ethnic minorities 

 
 
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are increasingly using computer technology and e-Health platforms,14 most people 
targeted by e-Health programs have been well educated, younger (<55 years), and 
White.14-17 These circumstances increase concerns that e-Health may intensify the 
“digital divide” and exacerbate health disparities for under-represented 
communities.14,18,19 In particular, restricted computer access and lower computer, 
health, and language literacy levels are significant barriers for underserved 
populations.14 Few websites have been designed for persons with less than a high 
school education,14 and few e-Health programs incorporate cultural factors in health 
communications.20 For web-based programs that do offer information in Spanish, 
content quality often has been substandard.21 This may help to explain why only 42% of 
Latino adults ages 55 and older use the Internet, compared with 57% of non-Latinos.19 
In response to these often-cited barriers, the state-of-the-science “virtual advisor” 
computer technology being employed in COMPASS requires minimal computer skills or 
literacy, and provides personally and culturally tailored physical activity advice and 
support in multiple languages.22 
The COMPASS Trial allows for a direct determination of program comparative 
effectiveness for the Peer vs. Virtual Advisor programs. It also provides the opportunity 
to explore which Latino adult subgroups may do best with which type of communication 
channel. Given the dearth of community-based clinical trials in the health promotion 
area that have specifically targeted low-income aging Latinos, the COMPASS Trial also 
presents a unique opportunity to evaluate recruitment channels of particular relevance 
to Latino adults. The study design and procedures, including recruitment, intervention, 
and assessment procedures, constitute the major focus of this paper. 

 
 
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2. Methods and Procedures 
The Stanford University School of Medicine Institutional Review Board approved the 
study protocol for the COMPASS (Computerized Physical Activity Support for Seniors) 
Trial. All study materials, including informed consent and recruitment, intervention, and 
assessment forms, were produced in English and underwent thorough translation into 
Spanish by certified translators. Participants provided written consent upon reviewing 
the consent form with a bilingual staff member. The trial was registered at 
Clinicaltrials.gov (#NCT02111213). 
2.1. Study design 
The primary aim of this randomized trial is to test whether the Virtual Advisor 
intervention is as efficacious as the Peer Advisor intervention in promoting significant 
12-month increases in weekly minutes of walking—a form of moderate-intensity activity 
that is readily accessible and appealing to substantial numbers of midlife and older 
adults across the socioeconomic spectrum.3,23 The study employs a cluster-randomized 
design of community centers located in neighborhoods with at least 20% midlife and 
older Latino residents.24 In addition to location, other factors that were considered in 
choosing community centers included interest and willingness of center staff to 
participate in the study, appropriate space to accommodate computer equipment for the 
Virtual Advisor or Peer Advisor sessions, and a steady flow of Latino midlife and older 
adults who utilize the center’s regular programs and services. Community centers were 
matched by geographic location and randomized to either the Peer Advisor or Virtual 
Advisor intervention arm. The comparative effectiveness of these two interventions 
constitutes the major objective of the study and is the focus of this paper. To take 

 
 
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advantage of the study design to begin to explore new dietary intervention strategies in 
this underserved population, an additional pilot substudy is also underway. As part of 
this pilot substudy, two other similar community centers (one in each county in which 
the study is located) have been selected to receive culturally adapted dietary 
information via mail and face-to-face modalities across the one-year study period.  
2.2. Study location and participants 
The study is located in two San Francisco Bay Area counties—Santa Clara and San 
Mateo counties. Approximately 26% of the population across these two counties report 
being of Latino or Hispanic ethnicity [www.census.gov, 2015 American Community 
Survey]. Latinos in the western U.S. come largely from Mexico and Central America.24 
Of those born outside the US, approximately 50% have lived here for 15 or more years. 
The following study eligibility criteria were used to enroll study participants: (a) ages 
50 years and older; (b) insufficiently active,3 i.e., engaged in less than 100 
minutes/week of moderate intensity activity over the past six months; based on initial 
study physical activity screening items (see below), followed by a ﬁnal baseline physical 
activity de- termination using the full CHAMPS questionnaire; 25 (c) able to safely 
engage in moderate forms of physical activities such as walking based on the Physical 
Activity Readiness Questionnaire;25 (d) living within close proximity to one of the study-
designated community centers to allow regular (e.g., weekly) attendance to the 
community center-based intervention sessions; (e) able to read and understand English 
or Spanish sufficiently to provide informed consent and participate in all study 
procedures; and f) planning to live in the area for the next twelve months. The study 
screen, typically by phone, to determine physical activity status included the following 

 
 
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questions: 1) In the last three months have you regularly participated (at least two times 
per week) in any physical activity that has increased your breathing, such as aerobics, 
brisk walking, dancing, swimming, or playing sports. If the participants answered “yes”, 
they were asked to describe how many days per week they regularly exercised and how 
many minutes per day. These numbers were multiplied to calculate the total number of 
minutes per week. If the total number was 100 min or more, the individual was deemed 
ineligible. If the total number of minutes per week was reported as < 100, then 
individuals were asked to report, in a typical or normal week over the past four weeks, 
the total number of minutes per week they engaged in dance, walking or hiking uphill, 
walking fast or briskly for exercise, and water exercises other than swimming. In- 
dividuals were deemed eligible if participation in the above exercises totaled < 100 min 
per week. A ﬁnal determination of study eligibility based on physical activity status 
occurred at baseline using the full CHAMPS questionnaire. 
2.3. Study participant recruitment and screening methods  
To enhance external validity, three complementary recruitment methods were 
employed: geographically defined targeted mass mailings, cultural media-based 
promotion, and community outreach.26-28 For the geographically defined targeted mass 
mailings, mailing addresses of residents in geographically defined Census block groups 
near the community centers were accessed via a private mail service company and 
selected based on age and Latino ethnicity. Introductory bilingual letters describing the 
study and business reply cards were sent to households, along with a toll-free number 
to call to obtain further study information and undergo initial screening for study 
eligibility. Those individuals judged to be initially eligible based on the telephone screen 

 
 
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were invited to attend a group study orientation session at their designated community 
center, during which time the study objectives and procedures were explained in further 
detail, all questions were answered, and interested individuals were scheduled for an 
individual baseline assessment visit also held at the community center. Those 
individuals found to be eligible and willing to enroll in the study were scheduled for an 
initial individual intervention session at the community center.  
To broaden the types of individuals enrolled in the trial, the targeted mass mailings 
were augmented with bilingual media-based promotion and community outreach.26-28 
The media promotional methods included study announcements placed in local Latino 
newspapers. As part of community outreach activities, study information was placed at 
participating community centers and was made available at local stakeholder events 
attended by bilingual study staff, such as health and resource fairs, back to school 
nights, Parent Teacher Association (PTA) meetings, local school council events, and 
parent group meetings, as well as neighborhood libraries, churches, local health clinics 
serving Latino adults, and local grocery stores.29 Study participants and others who 
expressed interest in the study also were encouraged to refer others or share study 
information.  
2.4. Study participant retention methods 
To promote high levels of participant retention across the 12-month intervention and 
assessment period, group-based study orientation sessions were employed following 
the telephone screening process and prior to baseline assessment to ensure that all 
individuals considering study participation were fully informed about the study 
objectives, what would be expected of them throughout the study, and what they in turn 

 
 
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could expect from the study staff. The interactive group session included the weighing 
of the pros and cons of participating in the study, along with related motivational 
interviewing techniques and behavioral strategies, such as structuring of realistic 
expectations related to study outcomes. This type of pre-enrollment educational session 
has been associated with high levels of study retention in health behavior change trials 
across periods lasting up to 18 months.30   
2.5. Peer Advisor recruitment and screening methods 
Recruitment of Peer Advisors was accomplished using a variety of strategies. Study 
interventionists worked with the community center staff to identify activities within the 
community center through which Peer Advisors might be recruited. In addition, study 
staff requested referrals of people who attended the community centers regularly and 
who center staff identified as potentially viable candidates for the Peer Advisor role. In 
addition to collaborating with the community centers directly, Peer Advisor recruitment 
was also conducted through collaborating with different agencies external to the 
community centers. These agencies included local social and civic service agencies 
along with educational institutions such as schools and libraries. In addition, some 
recruitment efforts occurred through partnering with local fitness centers and targeting 
their physically active population as potential study peer advisors.  
Peer Advisor eligibility criteria consisted of the following: (a) ages 30 years and 
older; (b) physically active on a regular basis (i.e., engaged in approximately 150 
minutes/week or more of moderate intensity physical activity over the past 12 months); 
(c) free of any medical problems that might make it difficult to participate in regular 
physical activity or serve as a Peer Advisor in the study (e.g., any unstable chronic 

 
 
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conditions); (d) willing to participate in the peer advisor 12-hour training program and 
volunteer an average of 2-3 hours per week to advise their participants on physical 
activity; (e) willing to participate in monthly Peer Advisor supervision meetings; (f)  able 
to read and understand English or Spanish sufficiently to provide informed consent and 
participate in all study procedures; and (g) planning to live in the area for the next 12 
months. Peer Advisor selection and training consisted of screening interested 
individuals by phone to determine initial eligibility. Eligible individuals then attended an 
orientation session during which time the study objectives and procedures were 
explained in further detail, all questions were answered, and interested individuals 
provided informed consent related to study confidentiality protocols and information 
sharing. Individuals then completed a 12-hour Peer Advisor training program based on 
the successful peer-led physical activity training programs conducted previously by the 
Stanford team.31-33  
2.6. Peer Advisor oversight and quality assurance methods 
Ongoing Peer Advisor oversight and quality assurance have been accomplished 
through monthly Peer Advisor supervision meetings, periodic review of Peer Advisor 
logs and notes completed after each Peer Advisor-participant advising session, and 
random check-ins by study staff with study participants. Each monthly study staff-led, 
group-based Peer Advisor supervision meeting lasts approximately 120 minutes and 
focuses on the following activities: (a) sharing among Peer Advisors of their experiences 
and challenges with their participants, along with receipt of problem-solving advice and 
ideas from study staff and other Peer Advisors; (b) ongoing physical activity-relevant 

 
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information and updates; and (c) provision of relevant resources such as tip pages and 
newsletters that Peer Advisors can use in their meetings with their participants. 
2.7. Peer Advisor retention methods 
In addition to the monthly supervision meetings, other Peer Advisor retention 
methods include annual informational and motivational workshops provided by Stanford 
investigators and staff, modest monetary payment for the general time commitment 
accompanying Peer Advisor activities (i.e., a $10 local store gift card received upon 
completion of each participant introductory intervention session; a monthly store gift 
card commensurate with the number of participant advising sessions completed that 
month, equaling $5.00 per advising session), intermittent receipt of low-cost project 
incentives (e.g., project apparel, project mugs and tote bags), and a certificate of 
completion honoring each Peer Advisor’s contributions to the project at the end of his or 
her study advising period.   
2.8. Development and delivery of study interventions 
The two physical activity interventions are based on the theoretically derived 
cognitive-behavioral advice and support strategies used in the evidence-based Active 
Choices physical activity counseling program and similar behaviorally based 
interventions in the field.34-37 The primary behavioral theory utilized in the program is 
Social Cognitive Theory38 combined with the contextual framework of the 
Transtheoretical Model.39 Social Cognitive Theory (SCT) recognizes the dynamic 
interplay of cognitive, behavioral, and social factors in influencing behavior change.38 
Among the variables derived from SCT are self-efficacy, the use of self-regulatory skills 
(e.g., self-monitoring, goal-setting), factors related to the physical activity behavior itself 

 
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(e.g., format, intensity), and social environmental factors (e.g., modeling, social support, 
feedback from others), as predictors of physical activity participation.40 Applications of 
the Transtheoretical Model to the health promotion area include the use of a range of 
behavioral and cognitive strategies aimed at an individual’s motivational readiness to 
change a particular behavior (e.g., consciousness raising and other cognitive 
approaches in the preparation and action phases early in the program; reinforcement 
management and related behavioral approaches in the later phase of the program).39 
The Virtual Advisor program consists of an embodied conversational agent (ECA)--
an interactive, animated computer character that simulates face-to-face counseling and 
support using simple speech as well as nonverbal behaviors (e.g., facial cues, hand 
gestures).41,42 (See Figure 1.) Individuals interact with it through touching one of several 
simple conversation boxes shown on the screen throughout the interaction, which 
eliminates the need to utilize a computer mouse, track pad, or keyboard. The 
conversation boxes are aimed at less than an eighth grade education level.41,43  
The ECA communication interface has been shown to be effective in changing 
behavior in individuals with little to no computer experience and low levels of health 
literacy.43 The initial adaptation of the Virtual Advisor program to the Latino population 
being targeted was accomplished through a smaller intervention study that preceded 
the current trial22 that was based on earlier work with embodied conversational agents 
(i.e., virtual advisors) conducted by Dr. Bickmore.42 This work was augmented with 
information from Dr. King et al.’s Active Choices physical activity intervention program.35 
The formative testing and pilot work that was conducted also suggested that “Carmen”, 
the virtual advisor, could be acceptable to other midlife and older ethnic minority groups 

 
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as well, including Asian, Filipino, and African-American adults. The intervention protocol 
derived from this prior work was applied, in conjunction with similar intervention work 
with peer advisors,44 in establishing a parallel physical activity counseling program 
delivered in the trained Peer Advisor arm.44 
Both individually adapted programs are delivered at each participant’s designated 
community center and focus in particular on walking and similar forms of moderate-
intensity physical activity. Both interventions begin with an introductory session that 
covers the following information:35 (a) review of the participant’s physical activity history, 
long-term goals, and anticipated barriers to and facilitators of regular physical activity; 
(b) provision of information on the physical activity national guidelines, safety tips, and 
community center resources; (c) co-creation of a weekly physical activity plan; (d) 
training in the regular use of a pedometer and a project calendar to log steps and 
walking minutes; and (e) scheduling of the next intervention appointment. 
 Following the introductory session, each session follows a standard counseling 
protocol that is similar across the two interventions and which generally consists of the 
following elements: greetings and introductory social dialogue, checking for important 
health changes, review of pedometer-measured steps and minutes walked since the 
last advising session, acknowledgement of successes, problem-solving around barriers 
to physical activity, provision of relevant information to continue with physical activity or 
to overcome barriers, goal-setting for the period between the current and the next 
advising session, scheduling of the next advising session, and summary and wrap up. 
The typical advising session for each intervention was developed to average 
approximately 10-15 minutes, and the general schedule of advising sessions for both 

 
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arms over the one-year intervention period, based on previous research,31,35 is as 
follows: weekly sessions for the first two months; and twice-per-month sessions for the 
remaining 10 months.   
In the Peer Advisor arm, peer advisors meet with their individual participants in a 
location within the community center that affords privacy. The Virtual Advisor, 
meanwhile, is housed on a dedicated computer (supplied by the study) located in a 
private, secure area at each designated community center receiving that intervention. 
Participants are trained in a brief introductory session with project staff and are provided 
with a private log-in to initiate sessions with the advisor. Similar to the Peer Advising 
arm, participants are taught to use an Omron pedometer (Omron Healthcare, Inc., 
model HJ-720ITC, Lake Forest, Ill, 60045, USA), which provides a valid, reliable daily 
step count under prescribed and self-paced walking conditions in normal-weight and 
overweight adults.45 Participants are instructed to wear the pedometer on a daily basis, 
and download it on the Virtual Advisor computer via USB port at each session. The 
Omron can reliably store data for up to 41 days. Participants also complete a brief 
survey of personalized information at enrollment (e.g., favorite entertainment, names of 
supportive relatives/friends) that is programmed into the computer to personalize Virtual 
Advisor dialogue. Participants are encouraged to wear headphones during Virtual 
Advisor sessions to ensure privacy. As described earlier, Virtual Advisor and Peer 
Advisor sessions include individualized social interaction, progress review based on 
downloaded pedometer information, personalized feedback and problem solving, and 
goal setting based on current progress.46 Educational information can be received if 
desired in both arms. 

 
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2.9. Intervention fidelity and quality assurance 
To maintain intervention fidelity and quality assurance in the Peer Advisor arm, 
trained staff members conduct regular quality control checks and activities as described 
above.31,47 Virtual Advisor quality assurance includes regular monitoring of system 
performance and backup along with participant log-in activity, and ongoing availability of 
a study helpline for participants and center staff to call for assistance in correcting any 
problems. A designated Stanford staff member is in regular contact (twice a month or 
more frequently as needed) with the Virtual Advisor programming and oversight team at 
Northeastern University to ensure that any problems that occur can be resolved in a 
timely manner.  
2.10. Assessment: Primary outcome measures 
The primary outcome is change in walking activity across the 12-month intervention 
period. Walking is assessed at three time points (baseline, six months, 12 months) 
using the four walking items from the validated CHAMPS questionnaire (interview 
format) for older adults, which is available in English and Spanish.48-50 The CHAMPS 
questionnaire assesses usual weekly minutes of walking over the previous 4 weeks. 
Such validated self-report instruments represent the most direct and reliable means for 
assessing walking patterns, given that device-based assessment tools (pedometers, 
accelerometers) typically capture more general movement levels beyond walking 
behavior. The CHAMPS walking items have been signiﬁcantly associated with 
pedometer steps in previous studies, and were sensitive to change in the earlier 
conducted Virtual Advisor physical activity intervention study in a similar group of midlife 
and older Latino adults.22 The CHAMPS total activity as well as moderate and more 

 
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vigorous physical activity (MVPA) variables have been consistently associated with 
objective physical activity measures in prior studies and therefore will be evaluated as 
secondary measures of physical activity in the COMPASS Trial.51,52 We will also 
describe the proportion of each arm meeting the national physical activity 
recommendations of at least 150 minutes/week of MVPA.3 
Physical activity measurement using the CHAMPS is accompanied by the validated 
Actigraph® accelerometer (model wGT3X) at each of the three assessment time 
points.53 The accelerometer provides objective information related to overall physical 
activity amounts and intensity (though not the types of activities engaged in). The 
accelerometry protocol from a large study of 860 older adults is being applied.54 The 
activity monitor is worn on the hip during waking hours for seven consecutive days at 
each time point, ensuring a sufficient number of days of physical activity data (at least 
five days is considered as complete data) commensurate with current physical activity 
studies in older adults.55 Participants are instructed to wear the accelerometer for at 
least eight hours per day during their waking hours. Wear-time validity will be 
determined through applying the wear and non-wear time analysis and classification 
algorithms reported by Choi et al.,56 and analysis and interpretation of the accelerometry 
data will be based on our prior investigations and those of other older adult 
populations.57 
2.11. Secondary outcome measures 
Secondary outcome variables of particular importance to aging Latino populations 
include the following: sedentary behavior, measured using a validated one-week recall 
survey responsive to change in older adults;58 body mass index (BMI), derived using 

 
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standard clinical assessment protocols for height and weight;50 resting blood pressure 
and heart rate, using standard protocols;50 and quality of life and well-being, measured 
with the 10-item Vitality Plus Scale assessing well-being constructs associated with 
regular physical activity in aging adults, including sleep quality, energy, mood, and 
pain.59  
In addition to the above outcomes, program safety and adverse events are being 
tracked in both intervention arms using standardized forms and protocols used in prior 
physical activity intervention trials.31,36 Also, overall participant acceptability ratings of 
the novel Virtual Advisor intervention are being assessed at the end of the 12-month 
intervention period via a 19-item computer program acceptability scale,60 a 4-item 
cultural congruity scale,61 and the Working Alliance Inventory’s 12-item bonding 
subscale.22,62 Similar program acceptability questionnaires are being collected in the 
Peer Advisor arm at 12 months.31 
2.14. Randomization of community centers to study arms 
Block randomization by county locale was used to assign ten community centers to 
the two major study arms. Centers were randomized in pairs by locale via coin toss by 
staff not involved in study assessment or intervention procedures. Allocation 
concealment was in place for each block of centers during the randomization process to 
minimize selection bias with respect to subsequent blocks. Assessment staff members 
are blinded to randomization assignment and masked to prior assessment data for each 
participant.  
2.15. Sample size calculation and data analysis plan  

 
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Sample size estimates have been developed to test the study's primary question 
related to whether the Virtual Advisor intervention is no worse than the intervention 
delivered by trained human advisors, i.e., a test of  non-inferiority.63 Using a two-tailed 
95% confidence interval on the effect size (Cohen’s d), the threshold of clinical 
significance between the two treatments, Δ, has been developed to demonstrate clinical 
noninferiority of the new intervention (Virtual Advisor) if the confidence interval lay 
completely above – Δ, while clinical noninferiority of the Peer Advisor intervention will be 
demonstrated if the confidence interval lay completely below + Δ. In this trial, the effect 
size (Cohen’s d) is the standardized difference between the change in walking 
minutes/week over the 12-month intervention period. The critical value of Δ is based on 
a clinically meaningful difference between arms of 30 minutes of walking per week,3 and 
a within-arm standard deviation of 90, accounting for clustering within centers.64 The 
noninferiority margin was based on a clinically meaningful difference, in one direction, 
between arms of 30 minutes walking/week,3 and a within-arm standard deviation of 90, 
accounting for clustering within centers (Δ=.30).64  
We calculated that a sample of 112 per arm (224 total) would provide 80% power to 
demonstrate noninferiority between the two interventions using a simple pre-post 
analysis. We plan to use a mixed-effects linear regression model. Mixed-effects linear 
regression effectively addresses both missing data and early dropout in “intent-to-treat” 
analysis.65,66 In addition, the multiple assessment time points in the trial (at baseline, 6 
months, and 12 months) will serve to provide more detailed information on changes 
over time relative to studies using pre-post assessment only.67 Twenty-one additional 
participants were recruited to protect against loss to follow-up. Similar mixed-effects 

 
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linear regression techniques will be used to address the secondary outcomes of 
interest, e.g., intervention impacts on well-being variables across the study period. 
3. Results 
3.1. Selection and description of study community centers 
Ten community centers located in Santa Clara and San Mateo Counties, California 
with at least 20% Latino households (range = 21-55% Latino households) living within a 
one- to five-mile radius from the center were identified and expressed interest in serving 
as a study intervention site. These sites were block-randomized by locale to either the 
Peer or Virtual Advisor arms. Soon after recruitment, one center experienced 
unforeseen changes in its administration that disrupted center operations and precluded 
center participation in the study. To ensure comparable participant enrollment in each 
study arm, additional participants were enrolled at the remaining four community 
centers assigned to that intervention arm.  
In each center, there were center staff who were willing to support the research team 
in reserving meeting space for clinical assessments, recruitment meetings, and, when 
relevant, Peer Advisor meetings. For the sites that received the Virtual Advisor, 
designated staff members were instructed on how to maintain the computer kiosk (i.e., 
refilling printer paper, providing minor technical support related to the computer such as 
making sure that it was switched on and that the touch screen remained clean, and 
contacting a member of the research team if needed.)  
All participating community centers offered, as part of their usual activities, a 
nutrition program for older adults as well as nonphysical activity-oriented classes and 
activities, such as bingo, karaoke, and arts and crafts. Additionally, 89% offered weekly 

 
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physical activity classes and had at least one general computer available for older 
adults visiting their center. 
3.2. Study participants enrolled and recruitment sources  
A total of 245 participants are enrolled in the primary trial (Peer Advisor arm: n = 
122; Virtual Advisor arm: n = 123). Participant baseline demographic and health 
characteristics are summarized in Table 1. The study participants range in age from 50 
to 87 years, and 79% are women, with about half of participants reporting being married 
or living with a partner. The predominance of women is common in such health 
promotion intervention studies, as is the reluctance of participants, especially from such 
lower-income communities, to report their household incomes. Forty-four percent of 
participants have high school or lower levels of education.  
The highest recruitment yield (88.7% of enrolled subjects) was obtained from the 
geographically defined and demographically targeted bilingual mass mailings aimed at 
the Census blocks surrounding the community centers. The total number of targeted 
letters mailed describing the study and inviting individuals to contact the study team for 
more information was 107,930. The total cost of the targeted mailing recruitment 
strategy equaled approximately $69,900.00.  
3.3. Results related to recruitment and enrollment of Peer Advisors 
During the recruitment process for Peer Advisors, 230 individuals expressed initial 
interest, and 119 individuals were found to be eligible based on the study’s Peer Advisor 
eligibility criteria. Of these individuals, 56 completed the Peer Advisor training 
requirement, and 36 initiated Peer Advisor activities with at least one participant. Over 

 
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the course of the intervention period, six Peer Advisors had to relinquish their peer 
advisor activities due to a move out of the area, medical illness, or the initiation of a new 
job which put constraints on their time. Their study participants were transferred 
successfully to other Peer Advisors with minimal difficulties.  
4. Discussion 
The COMPASS Trial is among the first studies to systematically compare the 
effectiveness of physical activity advice delivered by humans versus automated 
advisors in aging Latino adults. Insufficiently active Latino adults are at elevated risk for 
a variety of chronic diseases and conditions, yet have rarely been targeted for tailored 
physical activity advice and support using communication sources (i.e., trained peer 
advisors, virtual advisors) that have great potential for population transferability and 
reach. The use of community centers for intervention delivery provides a readily 
available intervention access point in many communities across the U.S., and the one-
year intervention period will provide insights related to initial physical activity adoption 
and more sustained behavioral maintenance. The multi-faceted recruitment plan allows 
for a more diverse and potentially generalizable sample, and the particularly high yield 
of the targeted mass mailings is notable, given its less frequent use in a number of 
community-based research studies. At least one study has shown that personalized 
direct mailings can increase response rates for Latino adults relative to non- targeted 
approaches. 68 While community-based promotores de salud (i.e., lay or peer advisors) 
are a known and effective mechanism for health promotion in Latino populations, the 
method has been limited by the ability to scale. If the technology-enabled Virtual Advisor 
proves comparable and cost-sensitive relative to the Peer Advisor arm, it represents a 

 
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scalable and replicable solution that could be readily integrated into current community 
and senior center infrastructures. 
While the primary aim of this trial is to compare the 12-month effectiveness of the 
Virtual Advisor relative to Peer Advisors, a similarly compelling goal is to explore, 
through the planned moderator analyses, which participant subgroups may do best with 
which type of intervention. Referred to as “the whiches conundrum”,69-71 ascertaining 
how best to target different interventions to different subgroups of people represents 
among the most important challenges currently facing the behavioral health and 
precision medicine fields.69 Similarly, the planned mediator analyses will provide initial 
information on which types of variables may be of particular importance for achieving 
intervention-related impacts on physical activity levels.  
5. Conclusion 
If the promising preliminary Virtual Advisor evidence obtained from the original pilot 
study 22 is confirmed in this comparative effectiveness trial, this intervention will 
represent a potentially low-cost, readily accessible option that could be broadly 
disseminated across a range of community settings (e.g., clinics, pharmacies, libraries, 
residential settings). As such, it has substantial potential to reduce the health disparities 
gap by influencing a key health behavior in underserved populations.72 
 
 
 
 

 
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HUMAN SUBJECTS 
Note: All investigators participating in the proposed research have completed the 
Human Participant Protections Education for Research Teams certification process in 
compliance with NIH and Stanford University or Northeastern University guidelines. 
I. 
Consent Procedures 
Prior to undergoing the initial telephone or face-to-face screening, the screening 
procedures will be explained and individuals will give verbal consent to answer initial 
eligibility questions (age, ethnicity, proximity to community center). Those who are 
initially eligible will then proceed to an information session where the study activities and 
procedures will be explained in greater detail. If interested in continuing at that point, 
individuals will read and sign an informed consent form approved by the Human Use 
Committee at Stanford Medical School. This consent form will describe the study 
assessment and intervention components of the project, and their rights as research 
participants. The consent form will inform individuals that all information is strictly 
confidential and will not be released to anyone without their written consent. They will 
be reminded that as volunteers they can terminate their participation at any time without 
negative consequences. They will be provided information to contact the Medical 
Committee for the Use of Human Subjects in Research at Stanford Medical School. 
II. 
Potential Risks 
The potential risks involved in this project include psychological complications resulting 
from the assessment procedures or medical risks associated with moderate intensity 
physical activity programs in persons in this older age group. 

 
 23 
Psychological risks of the evaluation. There is a remote risk that persons completing 
questionnaires focusing on behavioral or psychological content may become distressed. 
There is no evidence that any permanent psychological dysfunction has resulted from 
such assessments. 
Medical risks of physical activity programs. The major risks of physical activity programs 
by initially inactive persons aged 55 years and over are orthopedic and cardio-
respiratory. Orthopedic problems primarily are of the overuse variety and usually can be 
treated by rest and change in the mode of physical activity. Frequent minor problems 
can occur, including temporary soreness or irritation of muscles, tendons and joints. The 
likelihood of orthopedic and cardio-respiratory risks are greatly minimized through the 
use of a moderate-intensity physical activity program that involves mild to moderate-
intensity walking, as proposed in the current study, and a supervised, individualized, 
progressive approach to physical activity as proposed in the current program. 
III. 
Minimizing Potential Risk 
Study assessments will be conducted at the community centers by extensively trained 
and supervised study staff. 
Physical activity programs. To ensure participant safety in this study, we will apply the 
set of screening and oversight procedures that are recommended in the American 
College of Sports Medicine’s (ACSM) guidelines and that we have used successfully in 
our research studies over the past 30 years. As recommended in the current ACSM 
guidelines, to screen potential participants for appropriateness for the physical activity 
program, we will have each individual complete the Physical Activity Readiness 
Questionnaire (PAR-Q), an extensively validated and used screening questionnaire that 

 
 24 
has been used throughout Canada and the U.S. to screen individuals for community-
based physical activity programs. If individuals answer ‘yes’ to any of the medically 
related screening items, they will be directed to get physician clearance prior to entry 
into the study. This protocol has been shown to ensure participant safety without 
creating unnecessary medical expenses and barriers to participation for persons not 
deemed at risk for physical activity-related complications---an important issue for the 
low-income population being targeted. The use of a mild form of physical activity 
(walking) also diminishes risk. In addition, participants will be regularly monitored for 
any level of physical discomfort or injury as part of the virtual advisor and lay advisor 
programs, and all subjects will be evaluated for adverse events as part of the study 
assessments conducted every 6 months using the standard forms approved for use by 
the Stanford Institutional Review Board. 
 
The risks of injury resulting from participating in the prescribed physical activity 
programs will be minimized in several ways: 
- Exclusion from the study of any person with overt cardiovascular or orthopedic 
disease. 
- Individualized physical activity program aimed at slow, gradual progression of 
physical activity amount. 
- The use of moderate-intensity physical activity programs, involving walking, for 
all study participants. 
- Ongoing personalized instruction of participants as part of the evidence-based 
physical activity advisor programs. 
- Ongoing attention to and advice related to the experience of physical discomfort 
during physical activity as part of both evidence-based physical activity advisor 
programs. (In addition, standard advice from the current U.S. Department of 
Health and Human Services’ national physical activity recommendations 

 
 25 
concerning physical activity safety is provided as part of the health education 
attention-control program.) 
 
The content of the moderate-intensity physical activity program that is being targeted is 
commensurate with the current national guidelines for physical activity promotion in 
older adults. 
Confidentiality of participant data. Confidentiality of participant data will be maintained 
by handling individual data by ID number, rather than by name; storing all individual 
data in locked file cabinets and secured, password protected electronic hard drives and 
data servers; and not disclosing individual data to anyone other than project staff, 
except as requested by the participant in writing. 
Adverse event monitoring and reporting. Adverse events information will be collected at 
all assessment points and recorded on standard forms that have been used in our other 
studies. We will collect information on all potential types of adverse events, including 
musculo-skeletal soreness and injury, as well as major medical events including injuries 
or conditions that result in health care provider visits, hospitalization, etc. Consistent 
with NIH and Stanford IRB policy, adverse events will be promptly reported in writing to 
the NIH and Stanford IRB. 
IV. 
Risks versus Benefits 
We believe the risks involved with the proposed physical activity interventions and 
associated tests are very small. Our own experience in studies involving the 
assessments proposed and the encouragement of progressive, moderate intensity 
physical activity in screened participants in this age group has been very positive. We 

 
 26 
are not aware of a single long-term adverse reaction to such physical activity programs 
among the over 3,000 study subjects we have monitored over the past 30 years. 
We believe that all participants will benefit by learning (from the study questionnaires) 
about their health status and physical activity levels. Those who successfully improve 
their physical activity levels will have achieved desired goals. Over the study period, all 
participants will benefit from receiving health information. 
We believe society will benefit from the results of this project in that it will inform further 
research aimed at developing effective and appropriate physical activity programs for 
under-served ethnic minorities. It will shed light on how best to deliver physical activity 
advice to enhance adoption and maintenance of PA among Latinos using state-of-the-
art informational technology that could conceivably be utilized in a range of community 
and home settings, thus substantially broadening the reach of the physical activity 
counseling program to underserved populations at potentially lower-cost than traditional 
face-to-face or health care provider-delivered approaches. These are public health 
issues of immense proportions, particularly with the continued growth of the elderly 
segment of the U.S. population and the substantial prevalence of inactivity among that 
population segment. In summary, we believe the risks can be kept very low whereas the 
benefits to participants and society are quite substantial. 
Data and Safety Monitoring Plan 
In addition to ongoing (weekly) project oversight by our senior investigators, the 
project’s Data and Safety Oversight Committee, will meet at regular intervals (e.g., 
semi-annually or more frequently as indicated) throughout the project period to provide 
input and feedback related to study recruitment and retention rates, study eligibility 

 
 27 
determination issues, data completion rates, and adverse events. During the study, 
participants will regularly monitor any discomfort that they are experiencing from the 
moderate-intensity physical activity program (consisting of walking) and will report them 
to their physical activity advisor on a weekly basis. We will use this information to revise 
the interventions as necessary to ensure that any risks of injury or discomfort are 
minimized. 
 
Table and Figure Descriptions 
Table 1. Descriptive statistics for the trial sample and by randomization arm 
Figure 1. Screenshot of the Virtual Advisor (“Carmen”) 
Table 1 
Descriptive statistics for the sample and by randomization arm. 
 
 
All 
 
Virtual Advisor 
 
Peer Mentor  
Between group 
p  value 
Variable (categorical) 
N 
% 
N 
% 
N 
% 
 
Sex 
Women 
193 
78.8 
98 
79.7 
95 
77.9 
0.73 
Men 
52 
21.2 
25 
20.3 
27 
22.1 
Race/ethnicity 
Hispanic 
241 
98.4 
120 
97.6 
121 
99.2 
0.71 
Asian 
3 
1.2 
3 
2.4 
0 
0.0 
White 
1 
0.4 
0 
0.0 
1 
0.8 
Country of birth 
United States 
100 
40.8 
53 
43.1 
47 
38.5 
0.01 
Mexico, Central, South  America 
139 
56.7 
65 
52.8 
74 
60.7 
Other 
3 
1.2 
2 
1.6 
1 
0.8 
Missing 
3 
1.2 
3 
2.4 
0 
0.0 
Marital status 
Married or living with  partner 
125 
51.0 
59 
48.0 
66 
54.1 
0.11 
Not married or living with  partner 
118 
48.2 
63 
51.2 
55 
45.1 
Refused 
2 
0.8 
1 
0.8 
1 
0.8 
Education 
Less than High School 
62 
25.3 
27 
21.9 
35 
28.7 
0.42 
High school 
45 
18.4 
28 
22.8 
17 
13.9 
Some college 
80 
32.7 
39 
31.7 
41 
33.6 
College 
27 
11.0 
15 
12.2 
12 
9.8 
Postgraduate 
28 
11.4 
12 
9.8 
16 
13.1 
Missing 
3 
1.2 
2 
1.6 
1 
0.8 
Household income 
< $5000 to $34,999 
32 
13.1 
17 
13.8 
15 
12.3 
0.97 
$35,000 to $49,999 
23 
9.4 
11 
8.9 
12 
9.8 
$50,000 to $74,999 
30 
12.2 
16 
13.0 
14 
11.5 
$75,000  or greater 
45 
18.4 
21 
17.1 
24 
19.7 
Don't know, refused, missing 
115 
46.9 
58 
47.2 
57 
46.7 
 
Variable (continuous) 
Mean 
SD 
Mean 
SD 
Mean 
SD 
Age (yr.) 
62.3 
8.4 
63.1 
8.3 
62.4 
8.5 
0.82 
Years in US 
47.4 
17.0 
47.7 
17.2 
47.1 
16.8 
0.80 
Number in household 
3.5 
2.2 
3.7 
2.5 
3.3 
1.8 
0.16 
CHAMPS Q – baseline (min/wk.): 
Walking for exercise & leisure 
 
45.9 
 
91.6 
 
48.0 
 
98.1 
 
43.6 
 
81.4 
 
0.71 
Walking briskly 
3.7 
16.1 
5.1 
19.7 
2.3 
11.4 
0.18 

 
 28 
Moderate, vigorous activities 
23.5 
69.2 
22.4 
62.8 
24.6 
75.1 
0.81 
 
Fig. 1. Screenshot of the Virtual Advisor (“Carmen).  
 
 
 
 
 
 
 
 
 
 
 
 
 
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