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Health Disparities

HD: Effectiveness of Nutrition Intervention Methods (2010)

Citation:

Svetkey LP, Erlinger TP, Vollmer WM, Feldstein A, Cooper LS, Appel LJ, Ard JD, Elmer PJ, Harsha D, Stevens VJ. Effect of lifestyle modifications on blood pressure by race, sex, hypertension status, and age. J Hum Hypertens. 2005 Jan; 19(1): 21-31. PMID: 15385946

PubMed ID: 15385946
 
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:

To examine the effect of various lifestyle changes on blood pressure.

Inclusion Criteria:
  • Healthy adults with above-optimal blood pressure, including those with stage 1 hypertension
  • Age 25 or older with a body mass index of 18.5 to 45kg/m2.
Exclusion Criteria:
  • Individuals who were taking antihypertensive medication
  • Systolic blood pressure of 120 to 159mm Hg
  • Diastolic blood pressure of 80 to 95mm Hg
  • Regular use of drugs that affect blood pressure
  • Target organ damage and diabetes
  • Use of weight loss medications
  • Prior cardiovascular event, heart failure, angina, cancer diagnosis or treatment in past two years
  • Consumption of more than 21 alcoholic beverages in a week
  • Pregnancy or lactation.

 

Description of Study Protocol:

Recruitment

Participants were from six institutions. 

Design

Randomized, multiple interventions.

Intervention

The intervention lasted 18 months. This article includes the first six months after randomization, which was referred to as the period of primary outcome analysis.

  • Group 1: Established (Behavioral intervention with traditional lifestyle recommendations)
  • Group 2: Established plus DASH (Behavioral intervention with traditional lifestyle recommendations plus the DASH diet)
  • Group 3: Advice only comparison group.

Statistical Analysis

  • Linear model to describe the influence of treatment on change in blood pressure
  • Main effect for subgroup variables
  • Effects of confounding factors were assumed to be constant across subgroups
  • Three-way interactions were included for analyses that looked jointly at race and gender
  • GLM procedure in SAS version 8.2 was used for all analyses
  • P-value of less than 0.025 considered to be significant. Subgroup values were significant at P=0.05.
  • No multiple comparison adjustment is applied to tests of subgroup differences in treatment effects.

 

Data Collection Summary:

Timing of Measurements

  • Measurements obtained at baseline and six months after randomization
  • Blood pressure measurements obtained at every visit. Two blood pressure measurements were obtained, separated by at least 30 seconds.
  • Other regular measurements were weight, height, fitness level, waist circumference, fasting blood to measure glucose and lipids, 24-hour urine collection and seven-day activity recall
  • Participants completed questionnaires on angina, medications, symptoms and side effects
  • Unannounced 24-hour dietary recalls were completed by telephone interviewers on a week day and weekend at baseline and at six months.

Dependent Variables

  • Systolic blood pressure
  • Diastolic blood pressure.

Independent Variables

  • Behavioral intervention
  • Behavioral intervention plus DASH diet. 

Control Variables

Advice only comparison group.

 

Description of Actual Data Sample:
  • Initial N: 810 (308 males, 502 females)
  • Attrition (final N): 810
  • Average age: 50
  • Ethnicity: 34% African American
  • Other relevant demographics: 95% overweight, 38% hypertensives
  • Location: various research sites.
Summary of Results:
  • All three interventions were associated with lifestyle change
  • Changes in food intake associated with the DASH diet were comparable across groups
  • Hypertension and age were not significant determinants of lifestyle changes
  • There was significant three-way interaction between gender, race and the indicator for the Established treatment group
  • Significant three-way interaction with the Established plus DASH intervention
  • Blood pressure changes were greater in hypertensives than in non-hypertensives. There was statistically significant interaction in the Established plus DASH diet group.
  • The Established plus DASH diet group had significantly lower blood pressure in both age groups relative to the Advice Only group
  • For those 50 years and older, the Established plus DASH diet intervention significantly lowered both systolic and diastolic blood pressure as compared to the Established group.

 

 

 

Author Conclusion:

Greater blood pressure reduction was observed in subjects with the greatest lifestyle changes.

Funding Source:
Government: National Institutes of Health
Reviewer Comments:
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? No
  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%.) No
  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? N/A
  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? N/A
  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? Yes
  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? 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)? No
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? No
  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