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NC: Cardiovascular Disease Risk Factors (2007-2008)

Citation:

Howard B, Van Horn L, Hsia J, Manson J, Stefanick M, Wassertheil-Smoller S, Kuller L, LaCroix A, Langer R, Lasser N, Lewis C, Limacher M, Margolis K, Mysiw W, Ockene J, Parker L, Perri M, Phillips L, Prentice R, Robbins J, Rossouw J, Sarto G, Schatz I, Snetselaar L, Stevens V, et al. Low-fat dietary pattern and risk of cardiovascular disease: The Women's Health Initiative Randomized Controlled Dietary Modification Trial. JAMA. 2006 February 8; 295 (6): 655-666.

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

The objective of this study is to test the hypothesis that a dietary intervention, intended to be low in fat and high in vegetables, fruits and grains to reduce cancer, would reduce CVD risk.

Inclusion Criteria:
  • Females being post-menopausal
  • Consuming at baseline at diet with fat intake of 32% or more of total calories.
Exclusion Criteria:
  • Prior breast or colorectal cancer
  • Other cancers except non-melanoma skin cancer in the last 10 years
  • Medical conditions with a survival less than three years
  • Adherence concerns such as alcoholism
  • Type 1 diabetes
  • Frequent consumption of meals prepared away from home.
Description of Study Protocol:
  • Recruitment: Post-menopausal women aged 50 to 79 years, of diverse backgrounds and ethnicities, who participated in the Women’s Health Initiative Dietary Modification Trial
  • Design: Randomized controlled trial
  • Intervention: Intensive behavior modification in group and individual sessions. Designed to reduce total fat intake to 20% of calories and increase intakes of vegetables and fruits to five servings per day and grains to at least six servings per day.
Data Collection Summary:

Timing of Measurements

Longitudinal study with a mean follow-up of 8.1 years.

Dependent Variables

  • Height, weight, waist circumference, and blood pressure: Measured at annual visits using standardized procedures
  • Fasting blood samples: Collected at baseline and year one for all participants and from a 5.8% (N=2,816) subsample of women at Years Three and Six
  • Physical activity: Assessed at baseline and years one, three, six and nine from self-reported questionnaires. Physical activity was expressed as metabolic equivalent tasks per week.
  • Nutrient outcomes: All participants completed a Food Frequency Questionnaire (FFQ) at baseline and year one. Thereafter, one third of the participants completed the FFQ each year in a rotating sample.
  • Medical outcomes: Electrocardiograms (ECGs) were digitally acquired every three years. A medical update questionnaire was completed every six months.

Independent Variables

Intensive behavior modification in group and individual sessions designed to reduce total fat intake to 20% of calories and increase intake of vegetables and fruits to five servings per day and grains to at least six servings per day.

Control Variables

The comparison group received diet-related education materials.

Description of Actual Data Sample:

Location

40 US clinical centers.

Baseline Characteristics of the Dietary Modification Trial Participants
(N=48,835)

 
Characteristic
Intervention (N=19,541)
Comparison (N=29,294)
P-Value
Age Group at Screening
50-59
7,206 (36.9)
10,797 (36.9)
 
60-69
9,086 (46.5)
13,626 (46.5)
>0.99
70-79
3,249 (16.6)
4,871 (16.6)
 
Mean (SD)
62.3 (6.9)
62.3 (6.9)
0.99
Race and Ethnicity White
15,869 (81.2)
23,890 (81.6)
 
Black
2,137 (10.9)
3,129 (10.7)
 
Hispanic
755 (3.9)
1,099 (3.8)
0.76
American Indian or Alaskan Native
88 (0.5)
114 (0.4)
 
Asian/Pacific Islander
433 (2.2)
674 (2.3)
 
Unknown
259 (1.3)
387 (1.3)
 
Annual Family Income
<10,000
683 (3.7)
1,100 (4.0)
 
10,000-19,999
2,091 (11.4)
3,202 (11.6)
 
20,000-34,999
4,501 (24.5)
6,814 (24.7)
0.40
35,000-49,999
3,954 (21.5)
5,868 (21.3)
 
50,000-74,999
3,887 (21.1)
5,662 (20.5)
 
>75,000
3,293 (17.9)
4,948 (17.9)
 
Body Mass Index
<25
 5,072 (26.1)
7,585 (26.0)
 
25 to <30
6,940 (25.7)
10,446(35.8)
0.94
>30
7,442 (38.3)
11,126 (38.2)
 
First-Degree Relative with Premature MI No
14,064 (81.3)
21,079 (81.2)
0.79
Yes
3,239 (18.7)
4,887 (18.8)
 
Post-Menopausal Hormone Therapy, years
Estrogen alone
12,262 (62.8)
18,452 (63.0)
0.36
None
2,711 (13.9)
3,933 (13.4)
 
<5
4,568 (23.4)
6,909 (23.6)
 
>5
 
 
 
Estrogen + progestin
14,196 (72.7)
21,299 (72.7)
0.92
None
 2,768 (14.2)
 4,114 (14.0)
 
<5
2,576 (13.2)
 3,881 (13.3)
 
>5
 
 
 
Smoking
Never or past
18,039 (93.4)
27,009 (93.2)
0.33
Current
 1,273 (6.6)
  1,977 (6.8)
 
 
Hypertension
No
10,315 (57.5)
15,271 (56.8)
0.15
Yes
7,617 (42.5)
11,596 (43.2)
 
History of Hypercholesteremia with Medication No
15,231 (88.2)
22,761 (87.9)
0.29
 
Yes
 
2,034 (11.8)
 
3,138 (12.1)
 
Treated for Diabetes
 
No
18,673 (95.6)
27,955 (95.4)
0.50
Yes
866 (4.4)
1,336 (4.6)
 
History of CVD MI
363 (1.9)
548 (1.9)
0.92
Stroke
205 (1.0)
328 (1.1)
0.46
CABG surgery
 241 (1.2)
 321 (1.1)
0.17
Aspirin Use No
16,149 (82.7) 
23,980 (81.9)
 
0.03
Yes
3,391 (17.4)
5,314 (18.1)
 
Metabolic Syndrome No
679 (64.4)
1,056 (64.0)
0.94
Yes
393 (35.6)
608 (36.0)
 

 
Summary of Results:

Mean Changes in CVD Risk Factors at Year Three

Risk Factor
Intervention, Mean (SD)
Comparison, Mean (SD)
Difference             Mean (95% Cl)
Weight, kilogram
-0.7 (9.0)
0.6 (9.2)
-1.29 (-1.47 to -1.11)*
Body Mass Index
-0.2 (2.7)
0.3 (2.7)
-0.49 (-0.54 to -0.44)*
Waist circumference, centimeters
-0.4 (7.3)
0.5 (7.7)
-0.98 (-1.19 to -0.76)*
Physical Activity, METs per week
1.4 (11.7)
1.0 (11.4)
0.39 (0.16 to 0.63)*
Blood Pressure
Systolic
-2.2 (16.3)
-2.1 (16.4)
-0.17 (-0.49 to 0.15)
Diastolic -2.6 (9.4) -2.3 (9.4) -0.31 (-0.50 to -0.13)*
Cholesterol mg/dl
Total -10.2 (32) -6.9 (31.9) -3.26 (-6.53 to -0.00)**
LDL-C -9.7 (29.3) -6.2 (29.1)
-3.55 (-6.58 to -0.52)**
HDL-C
-0.7 (9.4)
-0.3 (10.2)
-0.43 (-1.42 to 0.57)
Triglycerides mg/dl
1.0 (0.4)
1.0 (0.3)
0.00 (-0.03 to 0.04)
Lipoproteins
.9 (0.5)
0.9 (0.5)
-0.01 (-0.07 to 0.05)
Glucose mg/dl
-1.7 (19.9)
-0.7 (21.6)
-1.06 (-3.06 to 0.93)

* Difference significant at P<0.001 from a two-sample test
** Difference significant at P<0.05 from a two-sample test.
Nutrient Intakes at Year Six

 
Intervention   Mean(SD)
Comparison    Mean(SD)
Difference             Mean (95% Cl)
Energy, kcal per day
1,431.8 (551.7)
1,546.2 (639.5)
-114.3 (-126.8 to -101.8)
Total fat, percent of energy
28.8 (8.4)
37.0 (7.3)
-8.2 (-8.3 to -8.0)
Saturated fat
9.5 (3.2)
12.4 (3.1)
-2.9 (-3.0 to -2.8)
Monounsaturated fat
10.8 (3.5)
14.2 (3.1)
-3.3 (-3.4 to -3.3)
Polyunsaturated fat
6.1 (2.1)
7.5 (2.1)
-1.5 (-1.5 to -1.4)
Protein
17.7 (3.4)
17.1 (3.5)
0.6 (0.5 to 0.6)
Carbohydrate
53.9 (9.9)
45.9 (8.8)
8.1 (7.9 to 8.3)
Dietary Fiber
16.9 (7.5)
14.4 (6.4)
2.4 (2.3 to 2.6)
Cholesterol milligrams per day
193.6 (118.7)
243.4 (143.2)
-49.9 (-52.7 to -47.2)
Vegetable and fruit, servings per
4.9 (2.4)
3.8 (2.0)
1.1 (1.1 to 1.2)
Grains, servings per day
4.3 (2.4)
3.8 (2.2)
0.5 (0.4 to 0.5)
Soy, servings per week
0.3 (1.0)
0.2 (0.9)
0.0 (0.0 to 0.1)
Nuts, servings per week
1.0 (1.7)
1.8 (2.5)
-0.8 (-0.9 to -0.8)
Fish, servings per week
2.0 (1.7)
2.0 (1.9)
0.0 (-0.1 to 0.0)

 

Author Conclusion:

This long-term dietary intervention in post-menopausal women, intended to reduce fat intake and increase intake of vegetables, fruits and grains, achieved an 8.2% of energy decrease in total fat intake but only a 2.9% of energy decrease in saturated fat intake and only modest increases in intakes of vegetables, fruits and grains. The intervention did not reduce risk of CHD or stroke.

Funding Source:
Reviewer Comments:

This large study demonstrates how difficult it is to facilitate changes in dietary and lifestyle behaviors in middle-aged women.

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.) 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? ???
  5.1. In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate? ???
  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.) ???
  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? Yes
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? Yes
  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? Yes
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