EAL

DLM: Omega-3 Fatty Acids (2009-2010)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To test the efficacy of a simple intervention to reduce risk factors for diabetes mellitus (DM) and coronary heart disease (CHD) in Alaskan Eskimos.

Inclusion Criteria:

Adults, 25 years of age and older, living in one of four villages in the Norton Sound Region of Alaska.

Exclusion Criteria:

Subjects were excluded if they chose not to participate or were absent from the village on the days when screening occurred.

Description of Study Protocol:

Recruitment

Screenings were conducted in four villages in the Norton Sound Region of Alaska. All villagers were invited to participate.

Design

Cross-sectional study.

Statistical Analysis

The screening followed the Strong Heart Study Protocol and consisted of a personal interview, physical examination, blood sampling and nutritional interviews using 24-hour recall and food frequency instruments. The latter were conducted the day before the blood sampling.
The Nutrition Data System (NDS) was used to translate dietary intake data for the 24-hour recall and food-frequency questionnaire (FFQ)
Daily nutrient intakes reported by NDS were imported into SAS for statistical analysis
Plasma fatty acid analysis was done at the University of Alaska Anchorage on plasma that was originally obtained after at least 12 hours of fasting. Plasma analysis was done using a gas chromatograph.
The concentration of fatty acids was determined using regression analysis. The ratio of the area of each fatty acid peak to the internal standard peak was plotted vs. the weight ratio of the fatty acid and the internal standard. The regression equation was used to calculate the concentration of fatty acids.
The 12-lead electrocardiogram (ECG) was taken using a Marquette system. ECGs were read by cardiologists at the Fitzsimons Medical Center and ASP cardiologists. Abnormal ECGs were coded at the Minnesota electrocardiogram center.
Visual examination of histograms and the Shapiro-Wils test evaluated the ability of each variable to conform to a normal distribution
Generalized linear models were constructed with the fatty acid variable as the dependent variable, and age and CHD category as the independent variables.

Data Collection Summary:

Timing of Measurements

FFQ, 24-hour dietary recall, medical history and physical exam obtained at baseline only.

Key Study Variables

Prevalence of CHD
Consumption of n-3 fatty acid from fish
Plasma n-3 fatty acid levels.

Description of Actual Data Sample:

Initial N: 454 Eskimos (214 men, 240 women)

Attrition (final N): 433 (208 men, 225 women)

Age: Individuals older than 24 years of age

Ethnicity: Eskimos

Location: Four villages in the Norton Sound Region of Alaska.

Summary of Results:

Coronary heart disease was found in 5.3% of participants, and possible CHD was found among 8.4%, for a total of 13.7% meeting the criteria for CHD
10 individuals had a diagnosis of “definite CHD” based on confirmed myocardial infarction (MI)
Four individuals had CHD diagnosis based on evidence in medical records of coronary angioplasty or bypass surgery, thrombolytic therapy or a positive angiogram
10 subjects had CHD based on evidence of angina pectoris by Rose questionnaire and Minnesota Codes 4.1 or 5.1 or verified possible MI
Five subjects had a diagnosis of “possible CHD” made on the basis of the Rose questionnaire
The remaining cases (n=33) were diagnosed using a variety of Minnesota Codes as defined in the Strong Heart Study
Two cases of self-reported MI that were not confirmed by either the ECG or the medical charts were not defined as having CHD
No differences were found in the consumption of n-3 fatty acids between those with and without CHD.

Author Conclusion:

High consumption of n-3 fatty acids does not provide total protection against the development of CHD with other risk factors
Adequate intake of n-3 fatty acids reduces risk of cardiac arrhythmia and sudden death and improves some CHD risk factors.

Funding Source:

Government:

NIDDK of NIH

Reviewer Comments:

The researchers identify the limitations as small sample size and that the participants were not randomly selected. There were more participants in the female and in the older age categories.

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?		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?	Yes
	2.2.	Were criteria applied equally to all study groups?	Yes
	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)	N/A
	3.2.	Were distribution of disease status, prognostic factors, and other factors (e.g., demographics) similar across study groups at baseline?	Yes
	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?	Yes
	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?	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?		N/A
	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?	Yes
	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?	Yes
	6.3.	Was the intensity and duration of the intervention or exposure factor sufficient to produce a meaningful effect?	Yes
	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?	Yes
	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?	N/A
	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)?	No
	8.6.	Was clinical significance as well as statistical significance reported?	No
	8.7.	If negative findings, was a power calculation reported to address type 2 error?	No
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