DFA: EPA/DHA and Cognitive Health (2011)
To evaluate the effect of fish oil supplementation on quality of life (QOL), including cognitive performance and depressive symptoms.
- ≥65 years of age
- Written informed consent.
- Score of greater than 16 on the Center for Epidemiological Studies Depression Scale (CES-D)
- Score of less than 21 on Mini-Mental State Examination (MMSE)
- Current or recent (less than four weeks) use of fish oil supplements
- Intake of fish more than four times per week or more than 800mg of EPA-DHA from fish per day as estimated by fish consumption questionnaire
- Current use of pharmacological antidepressants
- Current use of medication for dementia
- Consumption of more than four glasses of alcohol per day
- 80% adherence to capsule use during the two week placebo run-in period according to self report
- ≤65 years of age
- No written informed consent.
Recruitment
Recruited from independently living older Dutch population
Design
- Primary outcomes were cognitive performance and depressive symptoms
- Subjects randomized using computer-generated random numbers in stratified permuted blocks of size six
- Stratification factors included age, sex, MMSE test score and CES-D test score
- Intervention of one of the following for 26 weeks
- Daily dose of fish oil containing high dose EPA-DHA (about 1,800mg)
- Daily low dose EPA-DHA fish oil (about 400mg)
- Placebo dose of high oleic sunflower oil
- QOL assessed using short version of World Health Organization QOL questionnaire (WHOQOL-BREF)
- Self-administered and checked for completeness by a research assistant at the study center at baseline and after 13 and 26 weeks of intervention.
Blinding
Subjects and investigators blinded to assigned treatment type
Intervention
- Daily dose of EPA-DHA supplement for 26 weeks
- High dose of about 1,800mg: 1,093±17mg EPA and 847±23mg of DHA (roughly equivalent consuming eight portions of fish per week)
- Low dose of about 400mg: 226+3mg EPA and 176+4mg DHA (approximately equivalent to consuming one to two servings of oily fish per week)
- Placebo oil (high oleic sunflower oil)
- Capsules with fish oil or placebo oil were indistinguishable in appearance.
Statistical Analysis
- Analysis performed on an intention-to-treat basis
- To evaluate cognitive performance, a minimum sample size of 63 subjects per group were needed to detect a difference (power 80%)
- To evaluate depressive symptoms, a minimum sample size of 85 subjects per group were needed to detect a difference (power 80%)
- Two-sided P-value <0.05 considered statistically significant
- Baseline characteristics of treatment groups were compared using one-way analysis of variance (ANOVA) or Kruskal-Wallis for continuous variables and chi-square for categorical variables
- Differential changes in QOL between the three intervention groups were tested using ANOVA
- Dunnett test used to compare mean changes within the treatment groups with that of the placebo group
- Additional per-protocol analysis including adherent subjects only also performed
- Post hoc analysis performed for subgroups of men and women separately.
Timing of Measurements
- Self administered WHOQOL-BREF used to assess QOL at baseline and after 13 and 26 weeks of intervention
- Fasting venous blood sample for determination of n-3 PUFAs collected at baseline and after 13 and 26 weeks of intervention
- Information on medical history, drug use, alcohol consumption, smoking habits, educational level, marital status and physical activity level obtained using a questionnaire at baseline
- Food frequency questionnaire to estimate fish intake in the previous three months administered at screening, baseline and after 13 and 26 weeks of intervention
- Height measured at baseline and weight and waist circumference measured at each center visit.
Dependent Variables
Change in WHOQOL-BREF score
Independent Variables
EPA and DHA intake
Control Variables
- Fish intake
- Height
- Weight
- Waist circumference
- Medical history
- Drug use
- Alcohol consumption
- n-3 PUFAs from fasting venous blood sample
- Smoking habits
- Education level
- Marital status
- Physical activity level
- Adherence to treatments.
- Initial N: 302 subjects (55% male)
- Attrition (final N): 299 subjects
- Age: Mean of 69.8 years
- Ethnicity: Dutch, no further details discussed
- Other relevant demographics:
- Education level (low/middle/high percentage)
- High dose EPA/DHA: 10/54/35%
- Low dose EPA/DHA: 11/49/40%
- Placebo: 5/59/37
- Anthropometrics:
- BMI
- High dose EPA/DHA: 26.1±13kg/m2
- Low dose EPA/DHA: 26.2±3.4kg/m2
- Placebo: 26.5+3.9kg/m2
- No significant difference between groups
- BMI
- Location: Netherlands.
Key Findings
- Total baseline WHOQOL-BREF scores at baseline and after 13 and 26 weeks of intervention were comparable between the three groups
- High dose EPA/DHA: 110
- Low dose EPA/DHA: 107
- Placebo: 107
- After 13 and 26 weeks of supplementation, neither fish oil groups showed better total WHOQOL-BREF scores or better scores on any of the four domains as compared to the placebo group
- After 26 weeks, the mean difference in WHOQOL-BREF scores from placebo was -1.42 (95% CI= -3.4-0.57) in the high dose fish oil group and 0.02 (-1.95-1.99) in the low dose fish oil group
- Exploratory analysis according to sex showed a significant change after 26 weeks in men in the high dose fish oil group with a mean difference from placebo of -3.28 (CI= -1.95= -5.85-0.71)
- After 26 weeks, a significant difference in men in the high dose fish oil group was observed for the domain physical health (-1.0, 95% CI= -1.95 to -0.05) and for domain environment (-1.45, 95% CI= -2.55 to -0.35)
Quality of Life |
1,800mg EPA/DHA Mean (95% CI) P-value |
400mg EPA/DHA Mean (95% CI) P-value |
WHOQOL-BREF Total Score Week 13 |
-0.98 0.42 |
-1.07 0.35 |
WHOQOL-BREF Total Score Week 26 |
-1.42 0.2 |
0.02 1.0 |
Other Findings
- Reasons for withdrawal from study
- Nine subjects did not complete study
- Five subjects stopped due to gastrointestinal complaints
- Two subjects stopped because participation was too burdensome
- Two subjects died before the end of the intervention
- Nine subjects did not complete study
- Adherence to treatment
- Average adherence based on counts of returned capsules was high (99%, with only three subjects <80% based on individuals completing treatment).
- Average adherence based on counts of returned capsules was high (99%, with only three subjects <80% based on individuals completing treatment).
Study showed that daily supplementation with a low or high dose of EPA-DHA for 26 weeks had no effect on QOL in healthy older subjects. Adherence was excellent and did not differ between treatment groups. The dropout rate was low, at 3%, and cannot therefore explain the findings. More studies investigating the effects of n-3 PUFAs on QOL are warranted, especially in subjects with impaired QOL.
Government: | Netherlands Organization for Health Research and Development |
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? | 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) | Yes | |
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? | 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? | 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? | Yes | |
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.) | No | |
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? | Yes | |
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? | 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? | Yes | |
6.6. | Were extra or unplanned treatments described? | Yes | |
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? | 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)? | Yes | |
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? | Yes | |
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 | |