DLM: Trans-fatty Acids (2005)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

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:

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:

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

Description of Study Protocol:

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 Summary:

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)

Description of Actual Data Sample:

--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

Summary of Results:

--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

Author Conclusion:

--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 hydrogenated
Funding Source:
Government: NIH
Reviewer Comments:

--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
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