FNOA: Antioxidants (2011-2012)

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

To explore the hypothesis that a deregulation of the free copper pool in serum could be a determinant of the variability of the progression of cognitive decline in a group of patients with mild or moderate Alzheimer's disease.

Inclusion Criteria:
  • Patients with probable Alzheimer's disease, according to National Institute of Neurological and Communicative Disorders and Stroke-Alzheimer's Disease and Related Disorders Association
  • Mild or moderate cognitive impairment (score below 2 of the Clinical Dementia Rating) and a Mini-Mental State Examination (MMSE) score of 25 or less.
Exclusion Criteria:
  • Conditions known to affect copper metabolism and biologic variables of oxidative stress on the basis of past medical history and screening laboratory tests
  • Patients with a history of stroke, presence of focal neurologic signs, severe subcortical leukoencephalopathy, presence of hemodynamically significant neck and intracranial arteries stenosis or occlusion, or cardiopathy.
Description of Study Protocol:
  • Recruitment: Subjects recruited from two specialized dementia care centers: The Department of Neuroscience, Fatebenefratelli Hospital, Isola Tiberina, Rome, Italy and the IRCCS, Fatebenefratelli Hospital of Brescia, Italy
  • Design: Prospective cohort study
  • Blinding used: Implied with measurements
  • Intervention: Not applicable.

Statistical Analysis

  • Formal sample size calculation was not performed, however it was calculated that a sample size of 50 patients would result in a power of 86% (with bilateral alpha of 0.05)
  • Multiple-regression analysis was applied to test the potential confounding role of demographic characteristics and vascular risk factors, then the linearity of the relationship between metal and oxidative biologic variables alterations and severity of progression of cognitive impairment was tested using a polynomial regression and the best-fitting model was chosen.
  • Odds ratios and corresponding 95% confidence intervals were calculated.
Data Collection Summary:

Timing of Measurements

  • Measurements made at baseline and at one year
  • When admitted to the study, patients underwent a structured clinical interview, a neurologic examination, brain MRI, an extensive neurological assessment, biochemical measurements and apolipoprotein E genotyping.

Dependent Variables

  • Mini-Mental State Examination
  • Activities of daily living
  • Instrumental activities of daily living.

Independent Variables

  • Levels of copper, iron, zinc, transferrin, ceruloplasmin, peroxides, total antioxidant capacity, free copper and apolipoprotein E genotype were assessed through standard laboratory methods
  • Mild or moderate Alzheimer's disease. Patients were also receiving donepezil (five mg daily for three months and then 10mg daily).

Control Variables

  • Demographic characteristics: Sex, age and education
  • Vascular risk factors: Hypertension, smoking habits and hyperlipidemia
  • Baseline MMSE.
Description of Actual Data Sample:
  • Initial N: 107 patients recruited
  • Attrition (final N): 81 patients completed follow-up; 17% men
  • Age: Mean, 74.4±7.4 years
  • Ethnicity: Not reported
  • Location: Italy.
Summary of Results:

Key Findings

  • Patients at baseline had mild to moderate dementia (mean MMSE score, 20.5±3.5)
  • 65% of patients had a higher than normal free copper (less than 1.6mmol per L)
  • Patients who were carriers of the APOE-ε4 allele had higher levels of free copper than non-carriers
  • After one year, MMSE decreased by 3.2±3.9 points (P<0.001)
  • Free copper predicted the annual change in Mini-Mental State Examination, adjusted for baseline MMSE by means of a linear regression model: It raised the explained variance from 2.4% (with only sex, age and education) to 8.5% (P=0.026)
  • When the annual change in Mini-Mental State Examination was divided into less than three or more than three points, free copper was the only predictor of a more severe decline (predicted probability of MMSE worsening 23%; odds ratio, 1.23; 95% confidence interval, 1.03-1.47; P=0.022)
  • Hyperlipidemic patients with higher levels of free copper seemed more prone to worse cognitive impairment
  • Free copper at baseline correlated with the ADL and IADL clinical scales scores at one year
  • At baseline, higher levels of free copper corresponded to lower ADL scores at the one-year evaluation (RHO=-0.299, P=0.018)
  • The higher were free copper levels, the lower were IADL scores either at baseline (RHO=-0.0349, P=0.001) or at one year (RHO=-0.359, P=0.004). 

Pearson Correlations Between Annual Change in Mini-Mental State Examination and Biological Variables of Metals and Oxidative Stress in Serum

Variables

Annual Change in MMSE

Significance

Copper

0.219
0.050 

Zinc

-0.218

0.103

Iron
0.058
0.640
Transferrin
-0.111
0.347
Ceruloplasmin
-0.001
0.990
Free copper
0.256
0.021
Peroxides
-0.051
0.649
Total radical trapping antioxidant capacity
0.169
0.137

 

Author Conclusion:
  • These results show an association between copper deregulation and unfavorable evolution of cognitive function in Alzheimer disease
  • Further research is needed to establish whether copper is an independent risk factor for cognitive decline.
Funding Source:
Government: Italian Health Department
Not-for-profit
AFaR Foundation - Osp. Fatebenefratelli, Rome, Italy
Other non-profit:
Reviewer Comments:

Only 81 patients out of 107 completed the one-year follow-up. Authors note the following limitations:

  • Short duration of clinical follow-up
  • Need for patient selection that possibly resulted in sampling bias
  • Refusal to perform follow-up evaluation by some patients that reduced the number of subjects initially involved in the study.
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? Yes
  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? ???
  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%.) ???
  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? ???
  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? ???
  6.4. Was the amount of exposure and, if relevant, subject/patient compliance measured? Yes
  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? 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? ???
  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? 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? Yes
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