DLM: Hypertension (2010)
Citation:
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:
To quantify the contributions of body weight, physical inactivity and dietary factors to the prevalence of hypertension in Finland, Italy, the Netherlands, the United Kingdom and the USA.
Inclusion Criteria:
- Randomized controlled design
- Mean age of study population over 18 years
- Published after 1966.
Exclusion Criteria:
- Overlap with other publication
- Lack of blood pressure data
- Cointervention from which the effect of the risk factor could not be separated
- Pregnant or diseased subjects
- Non-placebo control group
- Pharmacological intervention
- Duration less than two weeks
- Blood pressure reductions over 30mm Hg.
Description of Study Protocol:
Recruitment
- Meta-analyses and quantitative reviews of non-pharmacological randomized trials were identified from MEDLINE and the Cochrane Library Database published between 1966 and March 2001, using appropriate MESH terms
- Trials were identified from the reference lists of these papers
- An additional MEDLINE search was completed for trials published after 1990.
Design
Meta-analysis.
Intervention (if applicable)
- The effect of risk factors on blood pressure was assessed
- Population attributable risk percentages (PAR%) for hypertension were computed for all risk factors in the five countries.
Statistical Analysis
- Pooled estimates with 95% confidence intervals were obtained for each risk factor using meta-regression analysis
- Blood pressure estimated were weighted for trial sample sizes and these estimates were used for calculation of PAR%.
Data Collection Summary:
Timing of Measurements
Database was created of trials containing all information.
Dependent Variables
- Prevalence of hypertension
- Blood pressure changes.
Independent Variables
- PAR percentages computed for body weight, physical activity and intake of coffee, alcohol, sodium, potassium, magnesium, calcium and fish fatty acids
- Risk factor level of the trial population.
Control Variables
- Trial design
- Duration
- Number of participants
- Size of intervention
- Age, gender.
Description of Actual Data Sample:
- Initial N: 646 publications met inclusion criteria, 393 were then excluded
- Attrition (final N): 253 trials were selected
- Age: Different age ranges reported based on studies for each variable
- Ethnicity: Not mentioned
- Location: Worldwide studies.
Summary of Results:
|
Variables |
Size of Intervention | Duration | SBP Change | DBP Change | SBP Change-Weighted by Sample Size | DBP Change - Weighted by Sample Size |
| Body Weight | -6.5±2.4kg | 24 weeks | -5.3 | -3.6 | -4.8 | -3.4 |
| Physical Activity |
2.5±1.1h/wk |
16 weeks | -4.2 | -2.5 |
-2.8 |
-1.8 |
| Alcohol | -41±17ml/day | Six weeks | -3.5 | -2.0 | -2.6 | -1.4 |
| Coffee | -4.9±0.9 cups/day | Eight weeks | -1.7 | -1.0 | -2.2 | -1.0 |
| Sodium | -2.1±1.2g/day | Four weeks | -4.1 | -2.5 | -2.5 | -2.0 |
| Potassium | 2.0±1.0g/day | Six weeks | -3.3 | -2.1 | -2.4 | -1.6 |
| Magnesium | 483±216mg/day | Eight weeks | -1.7 | -1.8 | -1.3 | -0.9 |
| Calcium | 1.2±0.4g/day | 10 weeks | -1.5 | -0.7 | -1.5 | -0.7 |
|
Fish Oil |
4.1±2.7g/day |
Eight weeks | -2.1 | -1.5 |
-2.1 |
-1.6 |
Other Findings
- Being overweight made the largest contribution to hypertension, with PAR% between 11% (Italy) and 25% (USA)
- PAR percentages were 5% to 13% for physical inactivity, 9% to 17% for high sodium intake, 4% to 17% for low potassium intake and 4% to 8% for low magnesium intake
- The impact of alcohol was small (2% to 3%) in all populations
- PAR percentages varied among populations for inadequate intake of calcium (2% to 8%), magnesium (4% to 8%), coffee (0% to 9%) and fish fatty acids (3% to 16%).
Author Conclusion:
- Diet and lifestyle have a substantial impact on hypertension in Western societies, with being overweight, physical inactivity, high sodium intake and low potassium intake being the main contributors
- For several risk factors, the impact on hypertension varied among populations, which is important in setting priorities in preventative strategies. Hypertension itself, however is not the outcome of primary interest.
- More research is needed to assess the impact of diet and lifestyle on the total cardiovascular risk profile, including serum lipids and oxidative stress and (cardiovascular) mortality
- For Europe, a standardized core population database for dietary and lifestyle exposures would be extremely useful to facilitate public health research in this field.
Funding Source:
| Not-for-profit |
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Reviewer Comments:
- Thorough analysis of 253 articles over long time span
- Authors note that risk factor interactions were not examined.
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Quality Criteria Checklist: Review Articles
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| Relevance Questions | |||
| 1. | Will the answer if true, have a direct bearing on the health of patients? | Yes | |
| 2. | Is the outcome or topic something that patients/clients/population groups would care about? | Yes | |
| 3. | Is the problem addressed in the review one that is relevant to dietetics practice? | Yes | |
| 4. | Will the information, if true, require a change in practice? | Yes | |
| Validity Questions | |||
| 1. | Was the question for the review clearly focused and appropriate? | Yes | |
| 2. | Was the search strategy used to locate relevant studies comprehensive? Were the databases searched and the search termsused described? | Yes | |
| 3. | Were explicit methods used to select studies to include in the review? Were inclusion/exclusion criteria specified andappropriate? Wereselectionmethods unbiased? | Yes | |
| 4. | Was there an appraisal of the quality and validity of studies included in the review? Were appraisal methodsspecified,appropriate, andreproducible? | Yes | |
| 5. | Were specific treatments/interventions/exposures described? Were treatments similar enough to be combined? | Yes | |
| 6. | Was the outcome of interest clearly indicated? Were other potential harms and benefits considered? | Yes | |
| 7. | Were processes for data abstraction, synthesis, and analysis described? Were they applied consistently acrossstudies and groups? Was thereappropriate use of qualitative and/or quantitative synthesis? Was variation in findings among studies analyzed? Were heterogeneity issued considered? If data from studies were aggregated for meta-analysis, was the procedure described? | Yes | |
| 8. | Are the results clearly presented in narrative and/or quantitative terms? If summary statistics are used, are levels ofsignificance and/or confidence intervals included? | Yes | |
| 9. | Are conclusions supported by results with biases and limitations taken into consideration? Are limitations ofthe review identified anddiscussed? | Yes | |
| 10. | Was bias due to the review's funding or sponsorship unlikely? | Yes | |