EAL

FNOA: Antioxidants (2011-2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To investigate the association between usual curry consumption level and cognitive function in elderly Asians.

Inclusion Criteria:

Older adults aged 60 or more years
Singapore citizens or permanent residents
One subject per household was randomly selected.

Exclusion Criteria:

Subjects with dementia were excluded from the analysis
Subjects who were unable to complete the MMSE due to stroke and dysphagia.

Description of Study Protocol:

Recruitment

Singapore National Mental Health Survey of the Elderly is a population-based study of a nationally representative sample of 1,092 older adults aged 60 or more years (72% response rate) conducted from February 15, 2003 to March 30, 2004
Survey used a sampling list of household addresses generated by probability sampling from the Department of Statistics' national database of dwellings in Singapore
Random sample was ethnically stratified with intentional over-sampling of Malays (33%) and Indians (19%) for enhanced precision of ethnic-specific estimates.

Design

Cross-sectional study.

Statistical Analysis

One-way ANOVA was used for significance testing
Weighted generalized linear modeling of MMSE scores on three categories of curry consumption was used, with polynomial contrast of linear and quadratic effects across categories, and the adjusted mean total MMSE score for the curry consumption groups with covariate adjustment was estimated.

Data Collection Summary:

Timing of Measurements

Data were collected in the subjects' homes by trained nurses and field interviewers in English, Chinese or Malay, from February 15, 2003 to March 30, 2004
Extensive information was collected on personal, social, behavioral and health-related variables that included detailed histories of medical conditions, medications, substance use, dietary intake including curry consumption, functional assessments and semi-structured diagnostic interviews for psychiatric disorders.

Dependent Variables

Cognitive function assessed through the Mini-Mental State Examination (MMSE).

Independent Variables

Self-reported curry consumption categorized into three levels ("never or rarely," "occasional" and "often or very often").

Control Variables

Self-reported history of vascular conditions including hypertension, dyslipidemia, coronary artery disease, stroke and diabetes, asthma, and chronic obstructive pulmonary disease
Alcohol consumption
Smoking
Consumption of NSAIDs such as aspirin and ibuprofen
Oral steroids
Visual and hearing impairments
Basic activities of living (Barthel Index)
Instrumental activities of living (Lawton scale)
Level of fitness, social and productive activities
Diagnoses of depression and dementia.

Description of Actual Data Sample:

Initial N: 1,092 older adults in original sample (72% response rate)
Attrition (final N): 1,010 elderly Asians. 77 subjects with dementia and five subjects with stroke and dysphagia were excluded.
Age: Aged 60 to 93 years in 2003, mean age 68.9 years
Ethnicity:
- 48% Chinese
- 33% Malays
- 19% Indians
Other relevant demographics: 34.5% had no formal education
Location: Singapore.

Summary of Results:

Key Findings

Mean MMSE score was 25.9±4.22 and the median score was 27.0
Majority of subjects consumed curry at least occasionally (once in six months), 43% consumed curry at least once a month to daily and 16% reported never or rarely consuming curry
Those who consumed curry "occasionally" and "often or very often" had significantly better MMSE scores than did subjects who "never or rarely" consumed curry
Compared with subjects who had never or rarely consumed curry, subjects with higher levels of curry consumption showed higher crude mean MMSE scores (P=0.004), as well as adjusted mean MMSE scores (P=0.023) when controlled for potential confounders. The test for linear trend was significant (P=0.029).
Similar results of associations of curry consumption with cognitive impairment (defined as MMSE scores of less than 23) were obtained
The crude odds ratio of association for "occasional" curry consumption was 0.62 (95% CI: 0.41 to 0.92) and for "often" curry consumption was 0.65 (95% CI: 0.44 to 0.97)
Adjusted for all potential confounding variables, the odds ratio for "occasional
curry consumption was 0.62 (95% CI: 0.38 to 1.03) and for "often" curry consumption was 0.51 (95% CI: 0.21 to 0.90).

Odds Ratio of Association of Curry Consumption with Cognitive Impairment (MMSE Score Less Than 23)

Curry Consumption	Crude Odds Ratio and 95% CI	Adjusted Odds Ratio and 95% CI
Never/rarely	1	1
Occasionally	0.62 (0.41, 0.92)	0.62 (0.38, 1.03)
Often	0.65 (0.44, 0.97)	0.51 (0.21, 0.90)

Author Conclusion:

In conclusion, we report tentative evidence of an observed association between curry consumption and better cognitive function in elderly Asian subjects. More firm evidence may come from further investigations of curry consumption in relation to Alzheimer's disease in longitudinally followed-up cohorts of elderly persons and from investigations that further characterize the specific neurocognitive functions that are enhanced by turmeric.

Funding Source:

Government:

Agency for Science, Technology and Research, Biomedical Research Council, Republic of Singapore

Not-for-profit

National Medical Research Council

Reviewer Comments:

Nationally representative sample.
Authors note that they did not control for other dietary factors.

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?		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?	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?	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?		???
	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.)	???
	5.3.	In cohort study or cross-sectional study, were measurements of outcomes and risk factors blinded?	???
	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?		Yes
	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?	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)?	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