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 nutrient intake, cognitive impairment and depression in the elderly, adjusting for confounding factors.

Inclusion Criteria:

Men and women aged 65 years and over living in the community.

Exclusion Criteria:

Subjects with cognitive impairment were excluded from the GDS assessment (cognitive score <28.4), since the GDS had been validated in subjects without cognitive impairment.

Description of Study Protocol:

Recruitment

Men and women aged 65 years and over living in the community were invited to attend a health check carried out in the School of Public Health of the Chinese University of Hong Kong, by placing recruitment notices in community centers for the elderly and housing estates.

Subjects were volunteers and the aim was to recruit a stratified sample so that approximately 33% were in each of these age groups:

65-69 years
70-74 years
75+years.

Design

Cross-sectional study

Blinding used

Not applicable

Intervention

Not applicable

Statistical Analysis

Wilcoxon rank-sum tests were used to compare the marginal distribution of age, socioeconomic status, and number of medical illnesses, while chi-square tests were used to compare the proportion of women, proportion who completed primary school, and the proportion with history of stroke, myocardial infarction, angina, congestive heart failure, and diabetes mellitus between those with and without depression and between those with and without probable dementia
Logistic regression analyses were carried out to examine associations between lifestyle and dietary variables, and CSID and GDS, controlling for confounders
Due to the skewness in distribution for the PASE score and dietary intake variables, these variables were categorized into three groups (lower, middle half, upper) and odds ratios were computed to compare the middle half and upper quartile groups with the lower quartile group.

Data Collection Summary:

Timing of Measurements

Questionnaires completed during health check.

Dependent Variables

Cognitive function assessed with cognitive part of Community Screening Instrument for Dementia (CSID)
Depression assessed using Geriatric Depression Scale (GDS)
BMI.

Independent Variables

Dietary intake assessed with seven-day food frequency questionnaire
Mean nutrient quantitation per day calculated using food tables
Validation of the food frequency was examined by comparing calculated 24-hour intake of total energy, sodium and potassium with estimated values of energy expenditure and 24 hour urinary sodium and potassium outputs.

Control Variables

Demographics
Educational level
Socioeconomic status collected using self-rated scale of one to 10
Medical history
Smoking
Alcohol intake
Physical activity assessed using Physical Activity Scale of the Elderly (PASE).

Description of Actual Data Sample:

Initial N: 3,999 men and women
Attrition (final N): 3,999 men and women
Age: Aged 65 years and older
Ethnicity: Assumed Chinese
Other relevant demographics: Not reported
Anthropometrics: Not reported
Location: Community-dwelling residents in China.

Summary of Results:

Key Findings

There were 604 subjects with cognitive impairment (CSI-D <28.4), 372 subjects with depression (GDS greater than eight) and 92 subjects with both cognitive impairment and depression
Those with cognitive impairment were older, rated themselves slightly higher in community socioeconomic status, included more women, those with lower educational level, and those with diabetes mellitus
Those with depressive symptoms were older, rated themselves lower in both socioeconomic measures, were of lower educational level, had more diseases, more stroke, myocardial infarction, heart failure, angina and diabetes
Both CSID and GDS scores were associated with co-morbidity, demographic and socioeconomic factors
Few associations between lifestyle factors such as smoking, alcohol intake, physical activity, nutrient intake and CSID scores were observed
Dietary factors inversely associated with GDS score include total fat intake, vitamins A, B2, B3, C, fiber and vegetables
In terms of nutrient density, iron and isoflavone intake were additional factors (odds ratio for iron less than 9mg/1,000kcal per day=0.66, 95% confidence interval: 0.45 to 0.97, odds ratio for isoflavone 2.8-9.7mg/1,000kcal per day=0.73, 95% confidence interval: 0.54 to 1.0).

Author Conclusion:

Association exists between intake of various nutrients and psychological health independent of other confounding factors in the elderly population. A follow-up of this cohort or interventional studies are needed to elucidate a cause and effect relationship.

Funding Source:

Government:

Research Grants Council of Hong Kong, CUHK 4101/02M

Reviewer Comments:

Authors note the following limitations:

Validity of self-rated status among those with cognitive impairment is uncertain
Study population may already have a fairly uniformly healthy lifestyle, with over 50% having daily walks and other forms of exercise, and very low alcohol consumption, with 50% of men and 85% of women being teetotallers
The instruments used for cognitive impairment and depression are screening instruments only and may not represent the situation in subjects with clinically diagnosed disease
Cross-sectional design
Accuracy of data obtained from food frequency questionnaire in those with cognitive impairment or depression is questionable.

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?	N/A
	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?		N/A
	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?	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?	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?		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?	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?	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?	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