DLM: Trans-fatty Acids (2005)
To use adipose tissue biomarkers of intake to examine the association between 16:1, 18:1, and 18:2 trans fatty acids and risk of MI.
Inclusion Criteria:
--people from the 18 counties of the metropolitan area of San Jose, Costa Rica
--men and women diagnosed as survivors of a first acute MI by 2 independent cardiologists between 1994 and 1998
--meet WHO criteria for MI
Exclusion Criteria:
Cases:
--died during hospitalization
--were ³75 years old on day of first MI
--physically or mentally unable to answer questionnaires
--had previous hospital admission related to CVD
Controls:
--ever had an MI
--not physically or mentally able to answer questionnaires
Study Protocol:
--case control study
----partially hydrogenated soybean oil is major source of 18:1 and 18:2 trans-FA, used by > 40% of subjects
Data Collection:
--visited all cases and controls at their homes to collect dietary and health information, anthropometric measurements, and biological specimens
--interview: provide SES, demographic, and health characteristics
--subcutaneous adipose tissue biopsy from upper buttock
--energy and nutrient intakes assessed with FFQ developed and validated for Costa Ricans
--FFQ used as validation to assess confounding factors that did not have good biomarkers of intake (eg SFA)
--1061 subjects recruited:
cases (n=530) matched by age, sex, and area of residence to a population of controls (n=531)
--participation: 97% for cases, 90% for controls
--48 cases and 49 controls excluded from analysis due to missing data
--final sample: 482 case-control pairs that included 712 men and 252 women
--Total adipose tissue trans-FA is associated with an increased risk of MI after adjusting for confounders (OR=1, 1.34, 2.05, 2.22, 2.94, p<0.01)
--18:2 trans-FA abundant in both adipose tissue and in partially hydrogenated soybean oil, margarines, and baked products (OR=1, 0.96, 2.09, 3.51, 5.05, p for trend < 0.01)
Other statistically significant:
--cases more likely to currently smoke (p <0.0001)
--cases had higher prevalence of diabetes and HTN (p<0.0001 for both)
--cases less physically active (p=0.045)
--cases had higher W:H ratio (p=0.0002)
--cases had less income than controls (p=0.0012)
--strong positive association between tissue trans-FA and income, µ-linolenic acid and linoleic and vitamin E
--alcohol had a negative association with tissue trans-FA
--same results of association when looking at each fatty acid (16:1, 18:1, 18:2), however 16:1 correlations are weaker
--adipose tissue 16:1 trans-FA also associated with MI (OR=1, 1.57, 1.39, 1.34, 2.58, p for trend < 0.05)
Not statistically significant:
--age, sex, and residence adjusted OR for 16:1 trans-FA showed no association with MI, however, after adjusting for established risk factors, subjects in 5th quintile showed higher risk than those in first quintile (OR = 2.32, 95% CI 1.24-4.33, p =0.02)
--adipose tissue 18:1 trans-FA were not associated with risk for MI
--health policies for trans-FA content in vegetable oils in developing countries should be established and implemented
--recommend that vegetable oils used in processed foods and for cooking should not be hydrogenatedGovernment: | NIH |
--added bonus to take tissue biomarkers to help decrease the reliability on memory or self-reported information and decrease interviewer bias
--Is it a problem that cases were so different than controls in major confounding variables such as: smoking, diabetes, HTN, physical activity, SES, and W:H ratio? They did, however, adjust later in a multivariate analysis.
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? | No | |
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? | No | |
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? | No | |
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.) | Yes | |
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? | 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? | Yes | |
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? | N/A | |
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? | N/A | |
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? | 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? | 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)? | 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 | |