EAL

FNOA: Antioxidants (2011-2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To examine the relationship between dietary factors and cognitive impairment.

Inclusion Criteria:

Participants in the Statewide Survey of Alabama's Elderly (1986-1987) with data on cognitive function and dietary intake along with basic demographic information were included.

Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment

All subjects were participants in the Statewide Survey of Alabama's Elderly (1986-1987). Participants were selected randomly using a multi-cluster sampling procedure from 13 counties in Alabama. Procedures ensured that the areas selected and individuals sampled were not comprised of only a subset of the population, or representing an interviewer bias for certain neighborhoods or age groups of eligible individuals.

Design

Cross-sectional study

Blinding used

Not applicable

Intervention

Not applicable

Statistical Analysis

Dietary intake frequency was categorized into yes (once or twice a week, or most days, or everyday) or no (less often than once a week, or never)
The MSQ scores were categorized into normal (score greater than nine) and cognitive impairment (score less than nine)
Chi-square tests, Cochran-Mantel-Haenszel Statistic, and simple and multiple logistic regression were used to examine associations between dietary intake and cognitive impairment
Cochran-Armitage Trend test was used to examine the dose-response effects.

Data Collection Summary:

Timing of Measurements

Basic demographic information, Mental Status Questionnaire (MSQ) score and dietary intake assessed through in-home interview.

Dependent Variables

Cognitive impairment assessed through Mental Status Questionnaire (MSQ)

Independent Variables

Dietary intake frequency of meat (pork, beef, lamb), fish, chicken or turkey, vegetables, fruit, milk, cheese, desserts, bread or cereal, and dried beans and peas

Control Variables

Age
Race
Sex
Education.

Description of Actual Data Sample:

Initial N: 1,056 subjects with complete data included, original N unclear
Attrition (final N): 1,056 subjects, 67% female
Age: Mean age 69±8.9 years (range 55-94 years)
Ethnicity: 73% white
Other relevant demographics: Mean 10.7±3.8 years of education (range one to 18 years)
Anthropometrics:
Location: Alabama.

Summary of Results:

Key Findings

The prevalence of cognitive impairment, as defined by an MSQ score less than nine, was 16.6% (n=175)
Intake of cheese was found to be inversely associated with cognitive impairment in a single logistic regression analysis (odds ratio=0.59, 95% confidence interval: 0.42 to 0.84, P=0.003) and in a multiple logistic regression analysis (odds ratio=0.68, 95% confidence interval: 0.47 to 0.99, P=0.04) after adjusting for basic socio-demographic factors and for other dietary factors.
Increased frequency of cheese intake was associated with decreased cognitive impairment (P=0.0034)
In the multiple logistic regression analysis, bread or cereal (odds ratio=0.37, 95% confidence interval: 0.14 to 0.97, P=0.044) was inversely associated with, and dessert intake was (odds ratio=1.70, 95% confidence interval: 1.12 to 2.59, P=0.013) positively associated with cognitive impairment
Intakes of meat (pork, beef, lamb), fish, chicken or turkey, vegetables, fruit, milk and dried beans and peas were not significantly associated with cognitive impairment.

Association Between Intake of Dietary Factors and Cognitive Impairment

Intake of Dietary Factors (yes/no)	Odds Ratio	95% Confidence Interval	P value
Meat (yes=904, no=152)	1.11	0.67, 1.84	0.69
Dessert (yes=767, no=289)	1.70	1.12, 2.59	0.013
Fish (yes=596, no=460)	0.77	0.53, 1.10	0.15
Chicken or Turkey (yes=916, no=140)	0.81	0.48, 1.36	0.42
Cheese (yes=778, no=278)	0.68	0.47, 0.99	0.047
Vegetables (yes=1,041, no=15)	0.73	0.21, 2.56	0.62
Fruit (yes=930, no=126)	1.14	0.65, 1.97	0.65
Bread or Cereal (yes=1,031, no=25)	0.37	0.14, 0.97	0.044
Milk (yes=817, no=239)	1.34	0.87, 2.05	0.18
Dried Beans and Peas (yes=585, no=471)	0.99	0.70, 1.42	0.97

Author Conclusion:

In conclusion, this cross-sectional study of community-dwelling elderly suggests that dietary intake of cheese and bread or cereal may have a protective effect against cognitive impairment, whereas intake of dessert may result in a higher risk of cognitive impairment. Although the reasons for a potential protective effect of cheese ingestion are unclear, the possible roles of dietary tyramine, micronutrients, and/or proportion of fat types, contained in cheese is intriguing. Additional research is needed to examine the possible protective role of tyramine against cognitive impairment. Further studies, preferably, with longitudinal design are also needed to corroborate these findings. Future research may address type, amount and chemical contents of cheeses and their possible protective effects.

Funding Source:

Government:

National Institute on Aging

Reviewer Comments:

Inclusion/exclusion criteria and original N unclear, but original sample was representative of population of Alabama. Dietary intake broken into yes/no categories-statistical analysis not very sophisticated. Authors note the following limitations:

Cross-sectional study
Data were collected for dietary habits at the time of interview, data on past dietary habits was not collected
Individuals with cognitive impairment were not evaluated for specific diagnosis and interviewees did not undergo extensive neuropsychological testing.

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?	Yes
	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.)	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?		???
	4.1.	Were follow-up methods described and the same for all groups?	No
	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%.)	No
	4.3.	Were all enrolled subjects/patients (in the original sample) accounted for?	???
	4.4.	Were reasons for withdrawals similar across groups?	???
	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.)	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?	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?	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?		???
	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?	No
	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)?	???
	8.6.	Was clinical significance as well as statistical significance reported?	???
	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