FNOA: Antioxidants (2011-2012)

Citation:
 
Study Design:
Class:
- Click here for explanation of classification scheme.
Quality Rating:
Research Purpose:

To examine the influence of multiple lifestyle behaviors on cognitive function in older persons living in an urban community.

Inclusion Criteria:
  • Participant in the Suwon Longitudinal Aging Study
  • Persons aged 65 and older in Suwon, Korea.
Exclusion Criteria:

None specifically mentioned.

Description of Study Protocol:

Recruitment

  • Data are from the Suwon Longitudinal Aging Study, an annual survey of older Korean adults from 2001 to 2003
  • An initial sample of 1,461 community-dwelling persons was acquired by age- and gender-stratified random sampling from the city's registry of persons aged 65 and older
  • A total of 977 were interviewed; 229 were not located, 142 refused, 109 were absent long-term and four did not participate for other reasons.

Design

Prospective cohort study 

Blinding used

Not applicable 

Intervention

Not applicable 

Statistical Analysis

  • Linear regression with generalized estimating equations was used in the analysis, controlling for sociodemographics and chronic conditions
  • Sensitivity analysis was also conducted by repeating the analysis after excluding subjects with MMSE-K<19, indicating severe cognitive impairment and dementia.

 

Data Collection Summary:

Timing of Measurements

Subjects were interviewed by registered nurses in 2001 with follow-up interviews in 2002 and 2003.

Dependent Variables

Cognitive function assessed by Korean version of the Mini-Mental State Examination

Independent Variables

  • Lifestyle behaviors included:
    • Physical activity: Meeting the recommendation of regular exercise of moderate or vigorous intensity, less than five times per week for >30 minutes each time or less than three times per week for >20 minutes each time
    • Smoking
    • Vegetable consumption assessed through food frequency questionnaire 
    • Social activity
    • Alcohol consumption.

Control Variables

  • Age
  • Gender
  • Marital status
  • Education
  • Lifetime occupation
  • Chronic conditions: Self-reported presence of physician-diagnosed diabetes mellitus, heart disease, hypertension and stroke.
Description of Actual Data Sample:
  • Initial N977 persons interviewed in 2001, 60.7% female
  • Attrition (final N): 
    • 645 interviewed in 2002 and 537 interviewed in 2003. 
    • Major reasons for dropout were typical of urban dwellers, such as moving out of the area and long-term absence.
    • Non-respondents and decedents, compared with respondents, had significantly lower baseline levels of cognitive function
  • Age: Mean age 73.0±5.7 years at baseline in 2001
  • Ethnicity: Not reported, assumed Korean
  • Other relevant demographics:
    • 56.4% were married
    • 34.6% did not have a formal education
    • 75.9% were non-smokers
    • 26.6% engaged in regular physical activity
  • Anthropometrics:
  • Location: Korea. 

 

Summary of Results:

Key Findings

  • Average MMSE-K score at baseline was 24.3±4.8
  • No significant change in cognitive function over the course of two years of follow-up was observed
  • MMSE-K scores showed an average decrease of 0.4±4.1 between year two and year one, but an increase of 0.6±3.9 between years three and two
  • All lifestyle behaviors showed independent association with cognitive ability, even after adjusting for the covariates
  • An incremental benefit of multiple lifestyle behaviors was evident, with those engaging in more positive behaviors exhibiting a tendency to have a higher cognitive score
  • A two- or three-factor combination of non-smoking, vegetable consumption, and social activity showed the strongest association with cognitive function (β=1.832, P<0.01).

Individual Health Behavior Factors Predicting Change in Cognitive Function in the SLAS

Lifestyle Factors Unadjusted

Adjusted for Age, Gender, Marital Status, Education and Lifetime Occupation

Additional Adjustment for Chronic Conditions

Additional Adjustment for Each of the Other Lifestyle Factors
Non-smoking  -0.461 (0.264) 0.475 (0.254) 0.544 (0.251), P<0.05 0.393 (0.253)
Physical Activity 

0.870 (0.194), P<0.01

0.462 (0.191), P<0.05

0.466 (0.192), P<0.05 0.310 (0.195)
Vegetable Consumption  0.703 (0.181), P<0.01  0.758 (0.178), P<0.01  0.743 (0.175), P<0.01  0.698 (0.176), P<0.01 
Social Activity  0.827 (0.188), P<0.01  0.720 (0.187), P<0.01  0.702 (0.186), P<0.01 0.626 (0.187), P<0.01 

 

Author Conclusion:

In this study, lifestyle behaviors in late life were found to be positively associated with cognitive function, with incremental benefits observed for engaging in multiple behaviors. The study results provide support for participation in physical and social activity, smoking cessation, and vegetable consumption, as a way to preserve cognitive function in later life. Further research would be needed to examine whether multiple health behavior change strategies would help to promote cognitive health for older adults living in the community.

Funding Source:
Government: Korea Health 21 R & D Project, Ministry of Health and Welfare, Republic of Korea
Reviewer Comments:
  • Only 537 interviewed after two years of follow-up in 2003 from initial sample of 1,461 community-dwelling persons
  • Non-respondents and decedents, compared with respondents, had significantly lower baseline levels of cognitive function
  • All data based on self-report.
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? No
  2.2. Were criteria applied equally to all study groups? N/A
  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? 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? ???
  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? No
  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? 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? No
  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