DF: Cardiovascular Disease (2008)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To examine the plasma lipoprotein/lipid response to oat bran-rich supplement giving during four weeks in overweight pre-menopausal women.

Inclusion Criteria:
  • Normal cycling pre-menopausal overweight women
  • BMI of 25kg/m2 and above
  • Aged from 18 years to 53 years.
Exclusion Criteria:
  • Irregular menstrual cycle; pregnancy; lactation; plans for pregnancy; use of oral contraceptives; use of medications affecting plasma steroid and lipid levels such as thyroid hormones, antihypertensive and antidiabetic medications, lipid-lowering agents, etc; chronic diseases requiring medication
  • Excluded from the analyses: Anemia, irregular menstrual cycle or abnormal thyroid (11); irritable bowel syndrome (one); personal reasons (eight); time concerns (three).

 

Description of Study Protocol:

Recruitment

Women were recruited from the greater Quebec City through newspapers and advertising on the Laval University campus.

Design

  • Randomized controlled clinical trial
  • All subjects had a run-in period for two weeks, in which they followed the National Cholesterol Education Program Step I diet. After this phase, subjects were randomly assigned to the Control Group without supplement or to the Treatment Group, which consumed oat-bran enriched muffin during four weeks.
  • Both groups followed the NCEP Step I diet during the treatment period. Muffins were prepared at home following instructions given by the researchers. Compliance was measured by asking the subjects to record muffin intake. Three-day food records were completed by each participant before the beginning of the study and at the end of each study phase. A questionnaire about possible secondary effects were completed during each phase. Physical activity was evaluated at baseline, two and six weeks.

Blinding Used

Not mentioned: Lab tests.

Intervention

  • Group Treatment: 28g per day of oat-bran enriched muffin (two per day)
  • Group Control: Two muffins per day without oat-bran.

Statistical Analysis

  • Paired Student's T-test to evaluate changes in metabolic variables
  • When differences between Control and Treatment Groups were assessed, Student's T-test was used
  • ANOVA was used to adjust for covariates
  • X2 analyses used to explore the differences in the secondary effects between Control and Treatment Groups.
  • Statistical difference was considered when P≤0.05.
Data Collection Summary:

Timing of Measurements

  • Plasma lipids and anthropometric parameters were measured at baseline and at two and six weeks
  • Dietary intake was measured in the beginning and end of study (baseline and six weeks).

Dependent Variables

  • Total cholesterol, triglyceride and HDL-cholesterol: Enzymatic assays
  • LDL-cholesterol: Calculated with the Friedewald formula
  • Apoprotein B: Immunoelectrophoretic method of Laurell
  • Apoprotein E
  • Waist circumference: Airlie conference standards
  • Weight (kg) and BMI.

Independent Variables

Oat-Bran Treatment Group vs. Control Non-Fiber treatment.

Control Variables

  • Age
  • Apo-E genotype
  • Weight change.
Description of Actual Data Sample:
  • Initial N: 57 F
  • Attrition (final N): 34 females; 16 in the Control Group and 18 in the Treatment Group
  • Age: Mean, 37.4 (Control Group) and 39.1 (Treatment Group)
  • Ethnicity: Not mentioned
  • Other relevant demographics: There was a tendency for HDL-cholesterol be higher in the Treatment Group, when compared with Control; 1.50±0.32mmol per L and 1.37±0.23mmol per L, respectively
  • Antropometrics: There was a tendency for higher BMI, weight and waist circumference in the Control Group. One woman with a BMI of 23.6 was included in the study.
  • Location: Laval Universtiy; Quebec, Canada.
Summary of Results:

Variables Treatment Group Control Group
Week 2 Week 6 Statistical Difference Week 2 Week 6 Statistical Difference
Total Cholesterol, mmol/L
4.55±0.76
4.67±0.89
NNSS
4.60±0.88
4.63±0.93
NS
LDL-C, mmol/L
2.69±0.71
2.69±0.92
NS
2.71±0.76
2.73±0.83
NS
HDL-C, mmol/L
1.35±0.30
1.49±0.32
P<0.001; P<0.05*
1.28±0.26
1.30±0.25
NS
Triglyceride, mmol/L
1.10±0.49
1.07±0.49
N.S
1.35±0.73
1.32±0.69
NS
Total-C/HDL Ratio
3.56±1.11
3.32±1.08
P<0.001
3.78±1.13
3.71±1.06
NS
LDL-C/HDL-C Ratio
2.15±0.87
1.95±0.89
P<0.001
2.25±0.86
2.21±0.87
NS
BMI
28.5±4.8
28.4±4.8
NS
29.4±3.8
29.1±3.8
P<0.05
Weight, kg
75.7±12.8
75.3±12.8
NS
80.4±12.0
79.7±12.2
P<0.05

Values are means ±SD
*Control Group vs. Treatment Group.

  • Results remained similar after adjustment for age, apo E genotype and weight change
  • Plasma total cholesterol, LDL and HDL, according to responders and non-responders (nine women from Control and 13 women from Treatment): Among responders, HDL was statistically increased in the Treatment Group (P=0.02), but not the total cholesterol. Although LDL-cholesterol decreased more in the Treatment Group, the difference was not statistically significant.

Other Findings

  • Following the run-in period, there was a decrease in energy intake (P=0.01); in fat intake (P<0.001); in the percentage of energy from fat, saturated fat and monounsaturated fat (P<0.001)
  • Dietary intake was not changed until the end of the study.
Author Conclusion:

"The results suggest that oat bran-rich foods have a beneficial effect on the metabolic profile of overweight women. Integration of these foods as part of a healthy diet may improve the caridovascular risk profile of women."

Funding Source:
Reviewer Comments:
  • Many statistical tests increases possibility of type 1 error using Paired and Sudent's T-tests to measure the same variables and type 2 error due to the small sample size
  • Results are limited for only overweight women without hypercolesterolemia and consuming higher fiber than the general population.
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? No
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) No
  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.) Yes
  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%.) Yes
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? Yes
  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? No
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? No
  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? No
  6.6. Were extra or unplanned treatments described? No
  6.7. Was the information for 6.4, 6.5, and 6.6 assessed the same way for all groups? Yes
  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? No
  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? No
  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)? No
  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