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NC: Diabetes Management (2007)

Citation:

The Diabetes Prevention Program Research Group. Achieving Weight and Activity Goals Among Diabetes Prevention Program Lifestyle Participants. Obesity Research. 2004; 12: 1,426-1,434.

 
Study Design:
Randomized Controlled Trial
Class:
A - Click here for explanation of classification scheme.
Quality Rating:
Neutral NEUTRAL: See Quality Criteria Checklist below.
Research Purpose:

To determine how demographic, pyscho-social and behavioral factors are related to achieving weight loss and physical activity goals in the DPP (Diabetes Prevention Program) lifestyle participants.

Inclusion Criteria:
  • At least 25 years of age
  • BMI of 24 or greater; 22 or greater in Asians
  • FBS of 95mg to 125mg per dL or up to 125mg per dL in Native Americans
  • Two-hour plasma glucose level after 75-gram glucose load of 140mg to 199mg per dL.
Exclusion Criteria:
  • Persons taking medications that may alter glucose tolerance
  • Persons with illnesses that could seriously reduce their life expectancy or their ability to participate in the trial.
Description of Study Protocol:

Recruitment

Partcipants randomly assigned from the DPP group from the larger study's database of July 31, 2001, to determine whether high-risk individuals for diabetes could reduce their risk through various interventions.

Design

Participants assigned randomly.

Blinding Used

No.

Intervention

  • Goal-based intervention with a goal of 7% weight loss and physical activity of at least 150 minutes per week
  • Participants were assigned an individual case manager and met with their case manager 16 times over the first six months of the program and completed a core curriculum
  • Participants were expected to be seen in person at least once every two months
  • A low-fat diet (less than 25% intake) was recommended and if that did not produce weight loss, calorie restriction was also recommended
  • Participants were instructed to self-monitor minutes of physical activity and fat grams consumed every day during the core curriculum and then one week per month over the remainder of the trial.

Statistical Analysis

  • X2
  • Logistic regression models.
Data Collection Summary:

Timing of Measurements

  • Baseline
  • End of core curriculum
  • Final intervention visit.

Dependent Variables

  • BMI (kg per m2)
  • Physical activity level in minutes: Self-reported 

Independent Variables

Intensive lifestyle intervention.

Control Variables

  • Demographic
  • Pycho-social
  • Behavioral.
Description of Actual Data Sample:
  • Initial N: 1,079; 734 female, 345 male
  • Attrition (final N): 952 (88%)
  • Mean age: 50.6 years.

Ethnicity

  • 53.7% white
  • 18.9% African-American
  • 8.6% Hispanic
  • 5.7% Native American
  • 5.3% Asian or Pacific Islander.

Other Relevant Demographics

  • 72.8% employed full-time
  • 65.6% married or living together
  • 39.3% household income of $35,000 to $75,000
  • 69% with two to four in household
  • 10.2% with Beck Depression Inventory Score of at least 11.

Anthropometrics

Similar on important measurements.

Location

27 centers nationwide in the US.

 

Summary of Results:

 

Variables

Exercise of ≥150 Minutes per Week Weight Loss of ≥7%

Statistical Significance

End of core curriculum

Final intervention visit

End of core curriculm

Final intervention visit

Employment Status

Full or part-time

73%

64%

47%

32%

P<0.001 at Final Intervention
Retired 84% 81% 56% 56%  
Other 73% 66% 54% 45%  
Marital Status

Married or living together

75%

67%

52%

36%

 

Other 73% 66% 44% 39%  
Income Under $35,000 75% 71% 45% 44%  
$35,000 to $75,000 75% 64% 49% 33%  
At least $75,000 73% 63% 55% 33%  

Refused

75%

71%

53%

34%

 

Number in Household

1

78%

65%

52%

47%

 
2 to 4
73% 67% 49% 35%  
5 or more 74% 70% 49% 35%  
Depression 0-10 75% 67% 51% 37%  

11 or more

67%

67%

42%

37%

 

Other Findings

  • Older age individuals was a strong predictor of success at meeting the weight loss and physical activity goal at both the end of the core curriculum and at the final intervention visit
  • Older individuals were also more likely to complete self-monitoring records and lower percentage of calories from fat than younger individuals
  • Older individuals were also more likely to adhere to multiple components of the lifestyle intervention
  • Men and thinner individuals were more likely to achieve the physical activity goal, both initially and long-term
  • Hispanic Americans and Native Americans were more likely to meet activity goals
  • Whites were more likely to achieve the weight-loss goal at the end of the curriculum, but at the end of the study there were no significant differences in weight-loss success among the ethnic groups
  • Depressive symptoms were unrelated to success at achieving the acitivity or weight-loss goals in DPP
  • Married individuals were more likely to meet the goal of weight loss at the end of the core curriculum
  • Individuals with lower income, retired people and those with only one person in the household were more likely to achieve the weight-loss goal at the final visit
  • The only psycho-social or demographic variable related to initial success at achieving the weight-loss goal was ethnicity.
Author Conclusion:
  • The authors did a thorough discussion on their findings: They discussed the strengths of the study (which included a large sample size), the diversity of the participants, the standardization of the intervention across a large number of clinical sites and the extended length of treatment interventions
  • They also stated the limitations of the study, such as the self-reported physical activity, which is usually overestimated
  • The possibility of a bias with the self-monitoring records could also be a factor in success.
  • The authors also did not include the dietary data in the analysis, since fat gram recommendations per day were individualized, based on the participant's weight.
Funding Source:
Government: NIDDK, NCMHD, NIA, Indian Health Service, CDC
Industry:
Bristol Myers Squibb, Parke-Davis
Pharmaceutical/Dietary Supplement Company:
Reviewer Comments:

Unsure of the reliability of the self-reported physical acitivity levels, which was one of the dependant variables that this study was reviewing.

Quality Criteria Checklist: Primary Research
Relevance Questions
  1. Would implementing the studied intervention or procedure (if found successful) result in improved outcomes for the patients/clients/population group? (Not Applicable for some epidemiological studies) Yes
  2. Did the authors study an outcome (dependent variable) or topic that the patients/clients/population group would care about? Yes
  3. Is the focus of the intervention or procedure (independent variable) or topic of study a common issue of concern to dieteticspractice? Yes
  4. Is the intervention or procedure feasible? (NA for some epidemiological studies) Yes
 
Validity Questions
1. Was the research question clearly stated? Yes
  1.1. Was (were) the specific intervention(s) or procedure(s) [independent variable(s)] identified? Yes
  1.2. Was (were) the outcome(s) [dependent variable(s)] clearly indicated? Yes
  1.3. Were the target population and setting specified? Yes
2. Was the selection of study subjects/patients free from bias? Yes
  2.1. Were inclusion/exclusion criteria specified (e.g., risk, point in disease progression, diagnostic or prognosis criteria), and with sufficient detail and without omitting criteria critical to the study? Yes
  2.2. Were criteria applied equally to all study groups? Yes
  2.3. Were health, demographics, and other characteristics of subjects described? Yes
  2.4. Were the subjects/patients a representative sample of the relevant population? Yes
3. Were study groups comparable? Yes
  3.1. Was the method of assigning subjects/patients to groups described and unbiased? (Method of randomization identified if RCT) Yes
  3.2. Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? Yes
  3.3. Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) N/A
  3.4. If cohort study or cross-sectional study, were groups comparable on important confounding factors and/or were preexisting differences accounted for by using appropriate adjustments in statistical analysis? N/A
  3.5. If case control study, were potential confounding factors comparable for cases and controls? (If case series or trial with subjects serving as own control, this criterion is not applicable.) N/A
  3.6. If diagnostic test, was there an independent blind comparison with an appropriate reference standard (e.g., "gold standard")? N/A
4. Was method of handling withdrawals described? Yes
  4.1. Were follow-up methods described and the same for all groups? Yes
  4.2. Was the number, characteristics of withdrawals (i.e., dropouts, lost to follow up, attrition rate) and/or response rate (cross-sectional studies) described for each group? (Follow up goal for a strong study is 80%.) N/A
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? N/A
  4.5. If diagnostic test, was decision to perform reference test not dependent on results of test under study? N/A
5. Was blinding used to prevent introduction of bias? Yes
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? Yes
  5.2. Were data collectors blinded for outcomes assessment? (If outcome is measured using an objective test, such as a lab value, this criterion is assumed to be met.) Yes
  5.3. In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded? N/A
  5.4. In case control study, was case definition explicit and case ascertainment not influenced by exposure status? N/A
  5.5. In diagnostic study, were test results blinded to patient history and other test results? N/A
6. Were intervention/therapeutic regimens/exposure factor or procedure and any comparison(s) described in detail? Were interveningfactors described? Yes
  6.1. In RCT or other intervention trial, were protocols described for all regimens studied? Yes
  6.2. In observational study, were interventions, study settings, and clinicians/provider described? N/A
  6.3. Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect? Yes
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  6.5. Were co-interventions (e.g., ancillary treatments, other therapies) described? N/A
  6.6. Were extra or unplanned treatments described? N/A
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? N/A
  6.8. In diagnostic study, were details of test administration and replication sufficient? N/A
7. Were outcomes clearly defined and the measurements valid and reliable? Yes
  7.1. Were primary and secondary endpoints described and relevant to the question? Yes
  7.2. Were nutrition measures appropriate to question and outcomes of concern? Yes
  7.3. Was the period of follow-up long enough for important outcome(s) to occur? Yes
  7.4. Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? Yes
  7.5. Was the measurement of effect at an appropriate level of precision? Yes
  7.6. Were other factors accounted for (measured) that could affect outcomes? Yes
  7.7. Were the measurements conducted consistently across groups? Yes
8. Was the statistical analysis appropriate for the study design and type of outcome indicators? Yes
  8.1. Were statistical analyses adequately described and the results reported appropriately? Yes
  8.2. Were correct statistical tests used and assumptions of test not violated? Yes
  8.3. Were statistics reported with levels of significance and/or confidence intervals? Yes
  8.4. Was "intent to treat" analysis of outcomes done (and as appropriate, was there an analysis of outcomes for those maximally exposed or a dose-response analysis)? Yes
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? Yes
  8.6. Was clinical significance as well as statistical significance reported? Yes
  8.7. If negative findings, was a power calculation reported to address type 2 error? N/A
9. Are conclusions supported by results with biases and limitations taken into consideration? Yes
  9.1. Is there a discussion of findings? Yes
  9.2. Are biases and study limitations identified and discussed? Yes
10. Is bias due to study's funding or sponsorship unlikely? Yes
  10.1. Were sources of funding and investigators' affiliations described? Yes
  10.2. Was the study free from apparent conflict of interest? Yes