Clinical Trial Details
— Status: Completed
Administrative data
| NCT number |
NCT00520611 |
| Other study ID # |
00985 |
| Secondary ID |
|
| Status |
Completed |
| Phase |
N/A
|
| First received |
August 22, 2007 |
| Last updated |
June 10, 2015 |
| Start date |
June 2007 |
| Est. completion date |
December 2009 |
Study information
| Verified date |
January 2010 |
| Source |
University of Pennsylvania |
| Contact |
n/a |
| Is FDA regulated |
No |
| Health authority |
United States: Institutional Review Board |
| Study type |
Interventional
|
Clinical Trial Summary
Obesity is a major cause of premature aging and the second leading cause of preventable
mortality in the United States, accounting for approximately 110,000 deaths per year.
Financial incentives have been effective in modifying a number of health behaviors but they
have rarely been applied to weight loss, and to the best of our knowledge never to weight
loss by low-SES obese veterans.
We propose testing two different approaches to using financial incentives to encourage
weight loss. In the first, we build on previous work showing the effectiveness of 'deposit
contracts', in which subjects are given the opportunity to put their own money at risk if
they do not lose weight. In this incentive condition, subjects receive a direct payment
conditional on daily weight loss, and an optional additional payment based on their own
contributions to the deposit contract. We will match their contribution 1:1 to make the
option of depositing their own money attractive to this predominantly low SES population. In
the second approach we build on our own prior work using lotteries to promote drug
adherence. In this incentive condition, participants are entered into a daily lottery, and
receive any payoffs they earn from the lottery only if they stay on track with their
weight-loss goal. Given their popularity in the general population, lotteries hold the
promise of providing a cost-effective means of motivating weight loss and making efforts to
lose weight more salient to obese patients.
Description:
Fifty-seven obese patients at the Philadelphia VAMC (BMI between 30-40) will be randomly
assigned to one of three conditions: weight monitoring only (WM), deposit contract incentive
(DC$+WM), or lottery-based incentive (L$+WM). Exclusion criteria for the study will be
minimal to maximize generalizability, focusing only on exclusions that may make
participation unfeasible or unsafe (myocardial infarction within 6 months; uncontrolled
hypertension, defined as BP>170 mm Hg systolic or BP>110 mm Hg diastolic; metastatic cancer,
self-report of 6 or more alcoholic beverages per day; schizophrenia; severe depression;
active substance abuse; inability to read or severe cognitive deficits that would preclude
ability to read consent form or fill out surveys). Patients with severe depression will be
referred for treatment and considered ineligible until effectively treated. This exclusion
is appropriate because those who are severely depressed are too ill to undertake weight
reduction and because weight loss is often a symptom of severe depression. Subjects will
also be asked how interested they are in losing weight (5 point scale, ranging from
extremely uninterested to extremely interested, minimum score of 3 for inclusion). Subjects
will be required to be between ages 30-70, as weight loss may be more difficult and less
beneficial in the elderly. No other exclusions will be applied, as we aim to make the study
as generalizable as possible. Initial screening of BMI's and comorbidities will be done
using the VALOR data system at CHERP. Subjects who on paper meet criteria will then be sent
letters and asked to call us if interested. The remaining eligibility criteria will be
assessed over the phone, and subjects who meet the criteria will be invited for an in-person
intake visit.
At the initial intake visit, study procedures will be explained, and staff will create a
linear graph depicting the course of weight loss required to lose 16 pounds over the course
of 16 weeks (see figure). Subjects who provide written consent to participate will be
randomized to one of the 3 arms at this visit. Participants randomized to one of the two
incentive arms will be informed of the incentive plan (described in detail below).
Physiologic measurements will be limited to weight and height which will be measured by our
staff. To minimize fluctuations in weight due to diurnal variation, subjects will be asked
to commit to having all morning appointments (e.g. between 8 and 1 pm) for both intake and
f/u visits if possible. For those who cannot come in mornings, they will be asked to commit
to coming in at approximately the same time in the afternoon for intake and f/u visits (e.g.
between 2 and 4 pm). As soon as possible, following the intake visit, all participants will
have a one-on-one consultation with a dietician (Kelly McBride) in which diet and exercise
will be discussed. During this session, participants will receive guidance on strategies for
weight loss.
Following this consultation, participants will be asked to return to PVAMC to see the
coordinator at CHERP once a month for each of four consecutive months to: be weighed (all
participants), receive any payment they have earned (DC$+WM) or (L$+WM), and complete a
follow-up questionnaire. Subjects will be instructed to drink only one 8 ounce glass of
liquid and have a small breakfast and/or lunch (Examples of a small breakfast would be 2
slices of whole grain toast with jelly or one serving of a whole grain cereal with skim milk
or a piece of fruit and glass of skim milk. Light lunch could include any of the ones listed
above, or a broth based soup or half of a turkey sandwich or half of a peanut butter) prior
to coming in for follow-up visits. To compensate subjects for their time and trouble, all
participants will receive a financial incentive each time they attend a monthly weigh-in,
regardless of whether or not they have attained their monthly weight loss goal. Subjects
will also receive a financial incentive for attending the initial intake visit and a
financial incentive for attending their appointment with the dietician (Kelly McBride) and
for coming to a f/u weigh in at 3 months after the incentives for weight loss cease. Those
in the two incentives conditions will be provided with daily feedback, as described below.
All such messages will be transmitted by text -enabled pagers that we will provide for the
duration of the study for this purpose.
Subjects will be asked to measure their weight each morning upon awakening, after urinating,
but before eating or drinking and to transmit it to the study administrator by telephone (by
leaving a message). We will provide scales that are accurate to 0.1 pounds to each subject
for use for the duration of the study. We will tell participants at entry into the study
that the scale is theirs to keep if they remain enrolled in the study for the duration but
that they will be asked to return them if they drop out of the study before then. These
scales will be calibrated initially to match the weights recorded by the scale used at
CHERP.
As mentioned above, there will be two different financial incentive conditions that we will
be testing, both of which have a strong conceptual basis and for which there is suggestive
evidence in the literature that these could be effective approaches to help obese patients
lose weight.
Patients randomized to the lottery financial incentives arm will be eligible for a daily
lottery prize with an expected value of $3/day (a rough estimate of the savings per day to a
health plan from reducing the incidence of type 2 diabetes and other consequences of obesity
by achieving weight loss of 10-20 lbs) only if, prior to the lottery being resolved, they
have reported a weight at or below their desired weight loss trajectory (see figure). The
lottery is tailored both to provide infrequent large payoffs (a 1 in 100 chance at a $100
reward) and frequent small payoffs (a 1 in 5 chance at a $10 reward). This is because
lottery players are motivated by both a forward looking element (fixation on large $
amounts) and a backward looking element - how often did I win.
The lottery is designed such that, each day, subjects who send their early morning weights
will receive rapid feedback about whether they won, and non-adherent subjects will receive
feedback about whether they would have won had they been adherent. Subjects will be asked to
choose a 2-digit number upon entry into the study, e.g. "27". Each morning subjects will be
asked to call in to report their weight from that morning. A two digit random number will be
generated for each day. If the last digit includes either a "2" or "7" (which has
approximately a 1 in 5 chance), and the subject reported a weight that was at or below their
target weight for that day, they would be eligible to win $10. If the number is "27" (a 1 in
100 chance) they would win $100. Information on whether they won would be transmitted to
them each day, via text message, so that they receive this feedback immediately. If a
subject does not report their weight that morning (by 12pm) or reports a weight that is
above the target weight (with an allowance for the inaccuracy of the scale), they will be
informed that they would have won the lottery that day had they been below target. We
believe that a desire to avoid the regret associated with not winning, but learning that one
would have won had one been adherent, will powerfully motivate subjects to adhere - beyond
what one might anticipate based only on the expected value of the rewards. Moreover, this
effect will probably strengthen with experience - i.e., after a given subject has
experienced the remorse of failing to obtain rewards that they would have received if they
had been adherent. Subjects who achieve a 20 pounds or more weight loss over the 16 weeks
will be eligible for a one-time bonus of at least $50.
Because the above daily weights are all self-reported, we will inform patients that they
will only receive the calculated amount they are due if their weight at their monthly
weigh-in is at or below their target weight (typically a 4 pound weight loss over 1 month).
A 0.2 pound differential will be allowed between the office scale reading and the
participant's reported weight at the time of their monthly visit to account for 0.1 pound
scale variances on either the office or take home scales (e.g. if a subject loses 3.8
instead of 4.0 pounds per the office scale, they will receive their full incentive). These
payments would be provided using the "Authorization and Invoice for Medical and Hospital
Services Form" that allows participants to be paid directly through VA Agent Cashier.
Deposit contract financial incentive ($+WM) participants will be paid a base amount
corresponding to $3 for each day they are on track toward losing 16 pounds of weight by the
end of the 16-week study. Specifically, they receive this payment for every day that their
weight is at or below the ideal threshold line (see figure). In addition, these participants
will be given the opportunity to contribute between $0-$3 per day of their own funds,
refundable at the end of the month only if they have met or exceeded their monthly weight
loss goal. As an incentive for participants to contribute to deposit contracts, we will
match their money 1:1. Thus, participants in this condition have the opportunity to earn as
much as $9 per day ($3 base payment plus their $3 plus our $3 match). Participants will
decide at the beginning of each month how much, if any, they wish to deposit for the
upcoming month. They can therefore change the amount of their deposit contracts from month
to month. Any deposit contract money that is forfeited by participants because they do not
lose a sufficient amount of weight will be contributed to a pool of money that will be
divided equally among all subjects who lose 20 pounds or more over the 16 weeks. The size of
this bonus will be not less than $50, with any shortfall to be made up by study funds.
Because not all subjects will complete the study at the same time we will give each subject
who is eligible for this bonus $50 at the final follow-up visit. If the eventual amount ends
up being more, we will mail them a money order or the "Authorization and Invoice for Medical
and Hospital Services Form" to make up the difference.
Participants will be asked to self-monitor their weight on a daily basis and to transmit it
to the central office by phone. Each morning before eating or drinking and after urinating,
participants will be asked to a) weigh themselves in their pajamas, b) record their weights,
and c) transmit their weight to the central office before 12 noon. To maintain comparability
between the lottery and deposit contract groups, every afternoon, participants will receive
a text message telling them whether they are below their threshold weight for payment and,
if they are, how much they have received; if they are not at or below their threshold
weight, how much they would have received if they had been. At their monthly weigh-in,
participants will be given a report that captures how their report weights compare to the
ideal weight loss trajectory sketched in the initial consultation session and giving them
information on how much they will be paid if these weights are accurate, as well as how much
they would have received if they had stayed on target.
The daily monitoring provides participants with a constant reminder of their weight loss
goals. This frequency was chosen based on the finding that people tend to adopt a narrow
(daily) frame of reference to diets, "rededicating" themselves to it at the start of each
day. The daily weigh-ins are designed to reduce binge eating by making participants
constantly "accountable" for their weight. The monthly feedback provides encouragement and a
symbolic reward for slow and steady weight loss.
Falsification of weights will be minimized because patients will only get paid the amounts
identified in the weekly reports if the degree of weight loss recorded at the monthly
weigh-ins done by our coordinator are consistent with their self reports.
A key aspect of the weight loss trajectory is that it can be reset at monthly intervals.
This feature is critical in the likely event that a person falls short of attaining a
monthly weight loss goal. Disheartened at the prospect of having to lose double the weight
in order to get "back on track" by the end of the next month, such a person might drop out
of the study. To avoid this problem, each person who has not reached the weight loss for the
previous month will be given the opportunity for a "fresh start." The overall weight loss
goal will stay the same, however, the slope of the trajectory will adjust (i.e. steepen)
such that the participant need not "binge diet" following a month of poor weight loss
performance (see "Fresh start trajectory" in figure, which assumes the subject lost 2 lbs.
instead of 4 lbs. in first month). Keeping the overall weight loss goal constant makes the
procedure fair for those participants who maintain the ideal trajectory, while adjusting the
slope of the weight loss line allows for subjects who have occasional slip-ups to stay
engaged and get back on track.
Our standard approach to receiving information from subjects will involve subjects calling
us by telephone. We will not require subjects to have access to a home computer and
electronic mail.
Weight Monitoring only participants (control group) will be given the goal of losing 16
pounds in 16 weeks but will receive usual care only, e.g. care provided by their regular
clinical providers. They will not be given any financial incentive to lose the weight. They
will be asked to come for a monthly f/u visit and weigh in, but will not receive any
communications between these visits from the study coordinator.
