Vitamin E
Cases: 18 counties of San Jose, Costa Rica. Case subjects: men and women survivors of first acute MI in one of three hospitals. Met MI definition: WHO definition, study cardiologist confirmed diagnosis
Controls: free-living subjects matched for age, sex, and area of residence
Cases: Died during hospitalization, ³75 years on day of MI, physically or mentally unable to answer questions.
Controls: prior MI, physically or mentally unable to answer questions.
Cases and controls were interviewed in their home. Interview: FFQ, sociodemographics, socioeconomic status, smoking status, physical activity, medical history, anthropometic data and biochemical samples.
Data collection:
- Cases: 26 ±10 days after the MI
- Controls: 31±15 days after MI of matched cases
Dietary: FFQ about previous year
Biochemical: collected after an overnight fast. Measured TG, TC, HDL-C. LDL-C calculated.
Subcutaneous adipose tissue biopsy: alpha and gamma tocopherol measured via high-performance liquid chromatography
1061 study participants
107 excluded
Final sample: 954 (712 men, 242 women); 475 cases/479 controls
Subjects taking vitamin E supplements were excluded (23 cases/25 controls) in some data analysis (see below).
Cases were more likely to be smokers and have DM, HTN and angina.
Odds Ratio, 95%CI, risk MI of dietary & adipose g-tocopherol (excluding Vit E supp users).
Dietary: P for trend: 0.44
Quintile |
Median Intake |
Cases |
Odds Ratio (95% Confidence Interval) |
1 |
5.3 |
94 |
1.0, - |
2 |
8.6 |
103 |
1.4, .72-2.75 |
3 |
13.8 |
88 |
0.82, .34-1.96 |
4 |
18.1 |
78 |
0.59, 0.2-1.71 |
5 |
22.9 |
84 |
0.72,0.22-2.32 |
Adipose Tissue (µ/g) Ptrend: 0.53
Multivariate and diet adjusted.
Quintile |
Median Intake |
Cases |
Odds Ratio (95% Confidence Interval) |
1 |
8 |
79 |
1.0, |
2 |
13 |
90 |
1.27, .66-2.46 |
3 |
17 |
92 |
1.02, .52-2.00 |
4 |
23 |
92 |
1.57, 0.77-3.2 |
5 |
34 |
94 |
1.31, 0.62-2.76 |
Odds Ratio, 95%CI, risk MI of dietary & adipose a-tocopherol (excluding Vit E supp users).
Dietary: P for trend: 0.93
Quintile |
Median Intake |
Cases |
Odds Ratio (95% Confidence Interval) |
1 |
5.7 |
104 |
1.0, - |
2 |
7.1 |
87 |
0.68, .33-1.39 |
3 |
8.2 |
90 |
0.86, .42-1.78 |
4 |
9.5 |
88 |
0.9, 0.41-1.97 |
5 |
12.3 |
78 |
0.83,0.33-2.06 |
Adipose Tissue: (µ/g) P for trend: 0.7
Multivariate and diet adjusted.
Quintile |
Median Intake |
Cases |
Odds Ratio (95% Confidence Interval) |
1 |
33 |
74 |
1.0, - |
2 |
59 |
102 |
2.59,1.35-4.98 |
3 |
82 |
87 |
1.42, 0.7-2.92 |
4 |
116 |
96 |
3.06, 1.43-6.51 |
5 |
166 |
88 |
1.42, 0.69-2.95 |
Odds Ratio, 95% CI, risk MI in highest compared to lowest quintiles of dietary and adipose tissue levels
(excluding supplement users)
Multivariate and diet adjusted.
|
g- tocopherol
|
a-tocopherol
|
N highest |
205 |
162 |
N lowest |
198 |
162 |
Odds Ratio, 95% Confidence Interval |
0.69, 0.25-1.86 |
1.46, 0.62-3.42 |
Odds Ratio, 95%CI, risk MI and total vitamin E
Including Vit E supp users:
Dietary: P for trend: 0.011
Quintile |
Median Intake |
Cases |
Odds Ratio (95% Confidence Interval) |
1 |
13.5 |
116 |
1.0, - |
2 |
18.3 |
98 |
0.51, .26-1 |
3 |
23.9 |
85 |
0.27, .12-0.6 |
4 |
29 |
85 |
0.22, 0.08-.59 |
5 |
37.1 |
91 |
0.24, 0.08-.68 |
Excluding Vit E supp users: P for trend: 0.52
Multivariate, diet, and use of Vitamin E supplements (yes/no) adjusted.
Quintile |
Median Intake |
Cases |
Odds Ratio (95% Confidence Interval) |
1 |
13.4 |
113 |
1.0, - |
2 |
17.8 |
87 |
0.74, .37-1.47 |
3 |
23.1 |
81 |
0.42, .19-.93 |
4 |
28.1 |
82 |
0.35, 0.14-.91 |
5 |
33.8 |
84 |
0.38, 0.13-1.09 |
In this case-control study, there was no evidence of an association between either dietary or adipose tissue g-tocopherol and non-fatal MI.
There was a small positive association between adipose tissue a-tocopherol and risk of MI.
There was a protective effect when comparing total vitamin E even in the multivariate model including other nutrients (data shown). This protective effect remained even after supplement users were removed.
Study strengths: Adipose tissue measurements to complement the dietary data. Benefits of supplementation can occur within 1 year, current data collection was done after MI. Adipose tissue good indicator of long-term intake (turn over is 2 years).
Study weaknesses: because of the discrepancy between a-totcopherol and total vitamin E results, it is possible that the tocopherol content of foods in the nutrient database is less accurate than those for total vitamin E.
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? | N/A | |
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? | N/A | |
1.2. | Was (were) the outcome(s) [dependent variable(s)] clearly indicated? | N/A | |
1.3. | Were the target population and setting specified? | N/A | |
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? | N/A | |
2.2. | Were criteria applied equally to all study groups? | N/A | |
2.3. | Were health, demographics, and other characteristics of subjects described? | N/A | |
2.4. | Were the subjects/patients a representative sample of the relevant population? | N/A | |
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) | N/A | |
3.2. | Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline? | N/A | |
3.3. | Were concurrent controls or comparisons used? (Concurrent preferred over historical control or comparison groups.) | N/A | |
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? | N/A | |
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%.) | N/A | |
4.3. | Were all enrolled subjects/patients (in the original sample) accounted for? | N/A | |
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? | 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.) | N/A | |
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? | 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? | N/A | |
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? | N/A | |
7.2. | Were nutrition measures appropriate to question and outcomes of concern? | N/A | |
7.3. | Was the period of follow-up long enough for important outcome(s) to occur? | N/A | |
7.4. | Were the observations and measurements based on standard, valid, and reliable data collection instruments/tests/procedures? | N/A | |
7.5. | Was the measurement of effect at an appropriate level of precision? | N/A | |
7.6. | Were other factors accounted for (measured) that could affect outcomes? | N/A | |
7.7. | Were the measurements conducted consistently across groups? | N/A | |
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? | N/A | |
8.2. | Were correct statistical tests used and assumptions of test not violated? | N/A | |
8.3. | Were statistics reported with levels of significance and/or confidence intervals? | N/A | |
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? | N/A | |
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? | N/A | |
9.2. | Are biases and study limitations identified and discussed? | N/A | |
10. | Is bias due to study's funding or sponsorship unlikely? | Yes | |
10.1. | Were sources of funding and investigators' affiliations described? | N/A | |
10.2. | Was the study free from apparent conflict of interest? | N/A | |