EAL

Vitamin E

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine whether dietary or adipose tissue g-tocopherol is associated with lower risk of MI.

Inclusion Criteria:

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

Exclusion Criteria:

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.

Description of Study Protocol:

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

Data Collection Summary:

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

Description of Actual Data Sample:

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.

Summary of Results:

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

Author Conclusion:

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.

Funding Source:

Reviewer Comments:

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
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