EAL

FNOA: Antioxidants (2011-2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the relation between intake of three common foodstuffs that contain flavonoids (chocolate, wine and tea) and cognitive performance.

Inclusion Criteria:

Participants in the Hordaland Health Study (HUSK) who completed a food frequency questionnaire

Exclusion Criteria:

Excluded if not included above.

Description of Study Protocol:

Recruitment

Participants recruited from the population-based Hordaland Health Study. The HUSK study was conducted from 1997 to 1999 as a collaboration between the University of Bergen, the University of Oslo, local health services, and the Norwegian Institute of Public Health.

Design

Cross-sectional study

Blinding used

Not applicable

Intervention

Not applicable

Statistical Analysis

Final fully adjusted models used throughout the paper were controlled for sex, education, history of CVD, smoking status, vitamin supplement use, diabetes and total energy intake
For comparison between the groups of chocolate, wine and tea intake, the chi-squared test or ANOVA was used
Estimated mean values of cognitive scores by combined intake of chocolate, wine and tea, adjusted according to the final model of cofactors, were obtained by the univariate ANOVA
Risk ratios for poor cognitive test performance were obtained by logistic regression analysis
Multiple linear regression analyses were used to examine significant associations between the cognitive test scores and average chocolate, wine and tea intake using both a sex-adjusted model and a model adjusted for the variables referred to in the final model.

Data Collection Summary:

Timing of Measurements

Participants underwent cognitive testing by trained nurses after the standard cardiovascular examinations of the National Health Screening Service were completed.

Dependent Variables

Cognitive test battery included:
- Kendrick Object Learning Test (KOLT)
- Trail Making Test, part A (TMT-A)
- Modified versions of the Digit Symbol Test (m-DST)
- Block Design, short form (m-BD)
- Modified version of the Mini-Mental State Examination (m-MMSE)
- Abridged version of the Controlled Word Association Test (S-task).

Independent Variables

Intake of flavonoid-rich wine, tea and chocolate assessed by food frequency questionnaire

Control Variables

Sex
Education
History of CVD
Smoking status
Vitamin supplement use
Diabetes
Total energy intake.

Description of Actual Data Sample:

Initial N: 2,841 participants in the HUSK study invited to attend, 2,197 agreed to participate
Attrition (final N): 2,031 participants, 55% women; those completing a food frequency questionnaire
Age: Aged 70-74 years
Ethnicity: Not reported
Other relevant demographics: Not reported
Anthropometrics: Not reported
Location: Norway.

Summary of Results:

Key Findings

Mean intakes among the participants were 3.8 (95% confidence interval: 3.5 to 4.2) grams per day for chocolate, 22 (95% confidence interval: 20 to 25) mL per day for wine, and 222 (95% confidence interval: 209 to 235) mL per day for tea
Participants who consumed chocolate, wine or tea had significantly better mean test scores and lower prevalence of poor cognitive performance than those who did not
Participants who consumed all three studied items had the best test scores and the lowest risks for poor test performance
The associations between intake of these foodstuffs and cognition were dose dependent, with maximum effect at intakes of approximately 10 grams per day for chocolate and approximately 75-100 ml per day for wine, but approximately linear for tea
Most cognitive functions tested were influenced by intake of these three foodstuffs, and the effect was most pronounced for wine and modestly weaker for chocolate intake.

Cognitive Test	Intake of Chocolate, Wine or Tea, N items	Poor Test Performance, N (percentage)	Odds Ratio (95% CI)	P for trend
KOLT	0	50 (15.1)	1.00
	1	73 (11.5)	0.77 (0.52, 1.14)
	2	50 (8.0)	0.54 (0.35, 0.83)
	3	16 (4.9)	0.36 (0.19, 0.67)	<0.001
TMT-A	0	54 (16.5)	1.00
	1	72 (11.4)	0.69 (0.47, 1.02)
	2	38 (6.1)	0.37 (0.24, 0.59)
	3	12 (3.7)	0.26 (0.13, 0.52)	<0.001
m-DST	0	46 (14.0)	1.00
	1	61 (9.6)	0.70 (0.46, 1.07)
	2	37 (5.9)	0.49 (0.30, 0.79)
	3	10 (3.0)	0.31 (0.15, 0.64)	<0.001
BD	0	24 (7.3)	1.00
	1	43 (6.8)	1.08 (0.64, 1.84)
	2	24 (3.8)	0.69 (0.38, 1.27)
	3	6 (1.8)	0.40 (0.15, 1.03)	0.029
m-MMSE	0	49 (15.0)	1.00
	1	62 (9.9)	0.72 (0.48, 1.08)
	2	42 (6.7)	0.57 (0.36, 0.90)
	3	10 (3.1)	0.33 (0.16, 0.69)	0.001
S-task	0	56 (17.1)	1.00
	1	83 (13.1)	0.82 (0.56, 1.20)
	2	40 (6.4)	0.44 (0.28, 0.69)
	3	13 (4.0)	0.34 (0.18, 0.66)	<0.001

Author Conclusion:

In conclusion, in a population-based study, we showed that intake of flavonoid-rich food, including chocolate, wine and tea, is associated with better performance across several cognitive abilities and that the associations are dose dependent. However, these results should be considered with caution, because they were based on food-based analyses of population data and so we cannot conclude that the observed dietary benefits are truly associated with the flavonoids in chocolate, wine or tea. We suggest that further studies should directly examine the flavonoid status and take into account other bioactive dietary substances in these foods.

Funding Source:

University/Hospital:

University of Oslo

Not-for-profit

Charles Wolfson Charitable Trust, Norman Collisson Foundation, Advanced Research Programme of Norway, Johan Throne Holst Foundation for Nutrition Research

Reviewer Comments:

Inclusion/exclusion criteria and sample not well described. Cognitive measures assessed with several modified versions, not necessarily valid or reliable. Authors note the following limitations:

We cannot exclude the possibility of residual confounding
Possibility of recruitment bias should be considered
Cross-sectional design
Self-reported dietary data collected from participants who are cognitively impaired or demented may be less reliable.

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)	N/A
	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)	N/A

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?		???
	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?	???
	2.2.	Were criteria applied equally to all study groups?	Yes
	2.3.	Were health, demographics, and other characteristics of subjects described?	???
	2.4.	Were the subjects/patients a representative sample of the relevant population?	???
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?	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.)	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?	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%.)	Yes
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	Yes
	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.)	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?	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?		???
	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?	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?	???
	7.5.	Was the measurement of effect at an appropriate level of precision?	???
	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