HTN: Fiber (2007)
- stage I isolated systolic hypertension (SBP 140 - 159 mm Hg, DBP < 90 mm Hg)
- participants in DASH trial
- Aged 47 +/- 22 years
Recruitment
DASH participants with stage I isolated systolic hypertension.
Design
Randomized Controlled Trial.
Blinding used (if applicable)
Not possible - lab tests.
Intervention (if applicable)
After 3-week run-in period on typical American (control) diet, participants were randomly assigned for 8 weeks to 1 of 3 diets, sodium content was same in all 3 diets and caloric intake was adjusted during the trial to prevent weight change.
- Continuation of control diet
- Diet rich in fruits and vegetables
- DASH diet
Statistical Analysis
All analyses made on an intent-to-treat basis. Between-diet differences in the change in blood pressure were tested with 1-way ANOVA with Bonferroni's adjustment for multiple comparisons. Significance of within-diet change in blood pressure was tested with paired t tests if normally distributed, signed rank test if not. 2-way ANOVA performed for diet/gender interactions. Abilities of diets to lower SBP to < 140 mm Hg were compared with chi-square test.
Timing of Measurements
Blood pressure was measured at baseline and at the end of the 8-week intervention period. Urine samples taken at the end of the run-in and intervention periods.
Dependent Variables
- Blood pressure measured with standard sphygmomanometry
Independent Variables
- Continuation of control diet, diet rich in fruits and vegetables or DASH diet
- Participants agreed only to eat foods that were provided
- Alcohol consumption limited to only 2 drinks per day
- 24-hour urinary excretion of sodium, potassium and creatinine to determine compliance
Control Variables
Initial N: Among 459 participants in DASH trial, 72 had stage I isolated systolic hypertension. Ccontrol group n=25 (60% female), fruits & vegetables n=24 (58% female); DASH n=23 (39% female).
Attrition (final N): 72 assumed, dropouts not discussed
Age: mean age Controls: 53.6 +/- 11.8 years, Fruits & Vegetables: 52.6 +/- 8.7 years, DASH: 54.7 +/- 8.1 years
Ethnicity: Controls: 36% nonminority, 64% minority; Fruits & Vegetables: 33% nonminority, 67% minority; DASH: 43% nonminority, 57% minority
Other relevant demographics:
Anthropometrics: fewer women in the DASH group, but the groups were similar in age, ethnicity, BMI and baseline BP.
Location: Boston
Other Findings
There were no significant changes in body weight among diet groups.
Use of the DASH diet significantly lowered SBP compared with the control diet (-11.2 mm Hg, 95% CI: -6.1 to -16.2 mm Hg, P < 0.001) and the fruits and vegetables diet (-8.0 mm Hg, 95% CI: -2.5 to -13.4 mm Hg, P < 0.01).
Overall, blood pressure in the DASH group fell from 146/85 to 134/82 mm Hg.
Similar results were observed with 24-hour ambulatory blood pressure measurements.
In the DASH diet group, 18 of 23 participants (78%) reduced their SBP to < 140 mm Hg, compared with 24% and 50% in the control and fruits & vegetables groups, respectively.
Government: | NHLBI, NCMHD, NCRR, NIH |
Quality Criteria Checklist: Primary Research
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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? | ??? | |
4.1. | Were follow-up methods described and the same for all groups? | ??? | |
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? | ??? | |
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? | 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? | 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? | 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)? | 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 | |