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HTN: Diet Patterns (2015)

Citation:

Elmer PJ, Obarzanek E, Vollmer WM, Simons-Morton D, Stevens VJ, Young DR, Pao-Hwa L, Champagne C, Harsha DW, Svetkey LP, Ard J, Brantley PJ, Proschan MA, Erlinger TP, Appel LJ. Effects of comprehensive lifestyle modification on diet, weight, physical fitness, and blood pressure control: Eighteen-month results of a randomized trial. Ann Intern Med. 2006; 144: 485-495. 

PubMed ID: 16585662
 
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 compare the 18-month effects of two multi-component behavioral interventions vs. advice only on hypertension status, lifestyle changes and blood pressure. 
Inclusion Criteria:
  • Healthy
  • Age 25 years and older
  • Pre-hypertension or Stage One hypertension and met the Joint National Committee VI (JNC VI) criteria for a six-month trial of non-pharmacologic therapy.
  • Not taking anti-hypertensive drugs
  • Systolic blood pressure of 120mm Hg to 159mm Hg and diastolic blood pressure of 80mm Hg to 95mm Hg based on the average of three screening visits.


 

Exclusion Criteria:
  • BMI lower than 18.5kg/m2 or higher than 45.0kg/m2
  • Use of hypertensive drugs or other drugs that affect blood pressure
  • JNC risk category C (target organ damage or diabetes)
  • Use of prescription weight loss drugs
  • Previous cardiovascular event
  • Congestive heart failure
  • Angina, cancer
  • Consumption of more than 21 alcoholic drinks per week.
Description of Study Protocol:

Recruitment

  • Direct mailing
  • Radio and newspaper advertisements
  • Networking within the local African-American communities.

Design

Multi-center, three-arm, randomized trial.

Blinding Used

Clinic staff  who were checking symptoms.

Intervention

  • Advice only (advice); established, guideline-recommended lifestyle recommendations (established); or established recommendations and adding the DASH dietary pattern (established plus DASH)
  • Advice only: Advice to follow National High Blood Pressure Education Program lifestyle recommendations for BP control (reducing weight, reduced-sodium diet, regular physical activity, heart-healthy diet including DASH diet). Advice in two 30-minute individual sessions, one immediately after random assignment and one after a six-month data collection.
  • Established and established plus DASH: Weight loss of 15 lb. in those with BMI 25kg/m2 or higher, at least 180 minutes per week of moderate-intensity physical activity, no higher than 100mmol per day of dietary sodium, and no higher than 1oz of alcohol for men and 0.5oz for women per day. Those on the DASH diet, increased fruits and vegetables (nine to 12 servings per day), low-fat dairy (two to three servings per day) and reduced saturated fat (7% or less energy) and total fat (25% or more energy). Both groups had 14 group and four individual sessions during the first six months and monthly group, and three individual sessions in seven to 18 months. Both groups kept food diaries, monitored dietary calorie and sodium intakes and recorded minutes of physical activity. 

Statistical Analysis

General linear model and logistic regression.

Data Collection Summary:

Timing of Measurements

Baseline, three months, six months and 18 months.

Dependent Variables

  • Blood pressure: Assessed twice at each measurement. SBP and DBP were calculated by using the mean of all available measurements.
  • Salt, vegetable and fruit intake: Took 24-hour urine collections
  • Weight: With light indoor clothing and no shoes
  • Fitness: Two-stage, 10-minute submaximal treadmill exercise test
  • Energy expenditure: Seven-day; interview administered physical activity recall
  • Adverse events: Blinded staff asked participants about gastrointestinal, musculoskeletal and cardiovascular symptoms and referred them for additional care as needed. 

Independent Variables

Diet: Diet intake was assessed by two 24-hour recalls, one obtained on a weekday and the other on a weekend.

 

 

Description of Actual Data Sample:
  • Initial N: N=810 (502 females, 308 males)
  • Attrition (final N): N=717
  • Age: Aged 50 years
  • Ethnicity: A total of 34% African-American, 2% other, 65% white.

Anthropometrics 

  • Mean SBP and DBP were 134.9mm Hg (SD, 9.6mm Hg) and 84.8mm Hg (SD, 4.2mm Hg), respectively
  • Among hypertensives, mean SBP and DBP were 143.9mm Hg (SD, 7.6mm Hg) and 87.5mm Hg (SD, 4.3mm Hg), respectively
  • In those without hypertension, mean SBP and DBP were 129.5mm Hg (SD, 5.8mm Hg) and 83.2 mm Hg (SD, 3.1mm Hg), respectively. 

Location

  • Portland OR
  • College Park, MD
  • Durham NC
  • Birmingham AL
  • Baltimore MD
  • Baton Rouge, LA.

 

Summary of Results:

Findings

  • Weight:
    • At 18 months, a mean weight loss from baseline was observed in each group
    • For both behavioral groups, the mean weight loss was statistically significantly greater than that for the advice group (net mean difference of -2.2kg for the established group and -2.7kg for established plus DASH; P<0.001 for each)
    • At 18 months, approximately 25% of participants in the two interventions groups met the weight loss goal of 6.8kg. 
  • Fitness:
    • At 18 months, fitness, as measured by heart rate at Stage Two of treadmill test, was improved all groups. There was no statistical significant difference between the groups. 
    • There were small increases in self-reported energy expenditure from baseline to 18 months, with no statistically significant differences between the two behavioral intervention groups and advice group. 
  • Urinary sodium and potassium:
    • At 18 months, reductions in urinary sodium excretion were significant for both intervention groups compared to the advice group
    • Urinary potassium excretion and and self-reported intake of dairy products also increased significantly in the established plus DASH group compared with the other two groups
  • Dietary intake:
    • The mean fruit and vegetable intake significantly increased in the established plus DASH group compared with the advice (2.6 servings per day) and the established (2.7 servings per day) groups
    • Total and saturated fat was significantly reduced in both intervention groups compared with advice, and in the established plus DASH relative to the established group
    • Dietary cholesterol intake was significantly reduced for the established plus DASH group compared with advice only and established groups
    • Energy intake was significantly reduced for the two intervention groups vs. the advice group
    • Intakes of calcium, magnesium, fiber and folate were all significantly higher in the established plus DASH group than in the advice and established groups.
  • Prevalence of hypertension and BP changes:
    • From baseline prevalence of 36% to 38% for hypertension, by 28 months it decreased in all three groups (32% in advice, 24% in established and 22% in established plus DASH)
    • Among those who had hypertension (HTN) at baseline, the prevalence of HTN at 18 months had decreased to 63% in advice, 40% in established and 38% in the established plus DASH
    • No participant had normal blood pressure at baseline; at 18 months, 18% of advice, 25% of established and 24% of established plus DASH had normal blood pressure (P>0.050 for each of the pairwise contrasts)
    • At 18 months, the mean SBP and DBP had declined from baseline for each group. Although the reductions were greater for the intervention groups, it was not statistically significant. 
  • There was no significant pairwise differences between behavioral intervention groups in the cumulative rate of occurrence of serious adverse events or other medical conditions. 



 

 

Author Conclusion:
Over 18 months, persons with pre-hypertension and Stage One hypertension can sustain multiple lifestyle modifications that improve control of blood pressure and could reduce the risk for chronic disease. 
Funding Source:
Government: National Heart, Lung, and Blood Institute
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? 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%.) ???
  4.3. Were all enrolled subjects/patients (in the original sample) accounted for? Yes
  4.4. Were reasons for withdrawals similar across groups? ???
  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? Yes
  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)? N/A
  8.5. Were adequate adjustments made for effects of confounding factors that might have affected the outcomes (e.g., multivariate analyses)? N/A
  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