EAL

FNOA: Antioxidants (2011-2012)

Citation:

Study Design:

Class:

- Click here for explanation of classification scheme.

Quality Rating:

Research Purpose:

To determine if CFH and LOC387715/ARMS2 genotypes influence treatment response to Age-Related Eye Disease Study (AREDS) type nutritional supplementation with antioxidants and zinc.

Inclusion Criteria:

AREDS study participants who were considered at high risk for developing advanced age-related macular degeneration (AMD) with DNA samples in the AREDS Genetic Repository.

Exclusion Criteria:

AREDS participants:

With AMD categories one, two and five
Without DNA samples
Not of white ethnicity.

Description of Study Protocol:

Recruitment

AREDS is a randomized, controlled clinical trial that enrolled 4,757 participants from 11 clinical centers.

Design

Retrospective cohort study

Using DNA extracted from venous blood of 876 white participants in AREDS category three and four were genotyped in the single nucleotide polymorphisms in the CFH (Y402H, rs1061170) and LOC387715/ARMS2 (A69S, rs10490924) genes. Adjusted unconditional logistic regression analysis was performed to assess the interactions of these genotypes to determine the relationship between CFH and LOC387715/ARMS2 genotype and treatment with antioxidants plus zinc.

Blinding used

Not indicated

Intervention

Supplementation with:

Placebo
Antioxidants
Zinc
Antioxidants and zinc.

Statistical Analysis

Adjusted unconditional logistic regression analysis was preformed to determine the presence of interactions between the progression of AMD, the presence of the genetic risk factors CFH genotype (TT, TC, CC) and LOC387715/ARMS2 genotype (GG, GT, TT) and treatment with AREDS supplements (antioxidants plus zinc) as compared with a placebo.
After finding evidence for a treatment interaction with antioxidants and zinc, testing for a preferential interaction between genotype and either of the two treatment components (zinc or antioxidants) was carried out
These secondary analyses were performed by comparing: Zinc vs. no zinc (participants taking study supplements containing zinc or study supplements containing no zinc) and antioxidants vs. no antioxidants (taking study supplements containing antioxidants or study supplements no antioxidants)
This provided more power to detect an effect from either of the components by approximately doubling the sample size in each analysis
Analyses were performed for interaction in the remaining treatment groups, comparing zinc vs. placebo and antioxidants vs. placebo, comparisons also carried out in the original AREDS report in evaluating treatment effect
The logistic regression was performed controlling for age, gender, education, smoking, and body mass index (BMI). The cross-product terms according to genotype (CFH and LOC387715/ARMS2) and the individual treatment factors (antioxidants, zinc and antioxidants, and zinc) were used to test for multiplicative interactions.
Odds ratios (ORs) and the corresponding 95% confidence intervals (CIs) were calculated for each of the risk factors.

Data Collection Summary:

Timing of Measurements

Patients in AREDS were examined every six months and stereoscopic fundus photographs were obtained routinely from all eyes at baseline, at the two-year follow-up visit and every year thereafter.

Dependent Variables

Intermediate AMD-advancement from category 3 to category 4
Bilateral advanced AMD-advancement from category 3 to category 5
Unilateral advanced AMD-advancement from category 4 to category 5.

With AMD stages defined as:

Category 3 (intermediate AMD): At least one large drusen (>125μm), extensive intermediate drusen or geographic atrophy not involving the center of the macula
Category 4 (advanced AMD): Central geographic atrophy or neovascular AMD in one eye or visual loss resulting from AMD regardless of lesion type
Category 5: Advanced AMD in both eyes.

Independent Variables

Genotype:

CFH
LOC387715/ARMS2.

Supplementation with:

Placebo
Antioxidants
Zinc
Antioxidants and zinc.

Control Variables

Age
Gender
Education
Smoking
BMI.

Description of Actual Data Sample:

Initial N: 876
Attrition (final N): 876
Age:

	Placebo	Antioxidant	Zinc	Zinc and Antioxidant
Age 50-69	58%	60%	53%	61%
Age 70-95	42%	40%	47%	39%

Ethnicity: White
Other relevant demographics:

	Placebo	Antioxidants	Zinc	Antioxidants and Zinc
CFH:
CC	29%	32%	35%	28%
CT	50%	51%	43%	50%
TT	22%	17%	22%	22%
LOC3877/ARMS2:
CC	42%	41%	38%	42%
GT	40%	45%	45%	47%
TT	18%	14%	17%	11%

Anthropometrics:

	Placebo	Antioxidant	Zinc	Zinc and Antioxidant
Gender:
Male	41%	41%	35%	44%
Female	59%	59%	65%	56%
Smoking:
Never	46%	39%	44%	44%
Past	46%	51%	49%	52%
Current	8%	10%	7%	4%
BMI:
<25	33%	35%	35%	28%
25-29.9	36%	44%	42%	44%
≥30	31%	21%	23%	28%

Location: USA.

Summary of Results:

Key Findings

AMD Progression:

The AMD status of 264 patients progressed during the study. The following chart shows the proportion of patients showing progression by treatment group:

Treatment group	Proportion with Progression
Placebo Group	36%
Antioxidants Alone	32%
Zinc Alone	30%
Antioxidants and Zinc	23%

Disease progression occurred in 36% fewer individuals in the group receiving antioxidants plus zinc than in the placebo group (OR, 0.54; 95% CI 0.34-0.84)
This finding is consistent with the initial AREDS findings which demonstrated a 25% reduction in progression to advanced AMD over five years in the group treated with antioxidants and zinc (OR, 0.66; 95% CI, 0.47-0.91). Also, consistent with previous findings, there was less of a treatment effect for zinc alone and antioxidants alone.

Effect of Genotype:

The homozygous risk genotypes in the two genes, CHF and LOC387715/ARMS2 confer ORs for progression of 2.76 (95% CI, 1.75-4.36; P<0.001) and 5.82 (95% CI, 3.64-9.32; P<0.001) compared with their homozygous non-risk genotypes
An interaction was observed between the CFH Y402H genotype and supplementation with antioxidants and zinc (CC; P=0.03)
In those individuals with the homozygous non-risk genotype (TT), 34% in the placebo group progressed to advanced AMD, compared with 11% in the antioxidants plus zinc-treated group, a reduction of approximately 68%
In addition, an interaction (P=0.004) was observed in the groups taking zinc vs. those taking no zinc, but not for groups taking antioxidants when compared with groups taking no antioxidants
Participants who were homozygous for either the non-risk allele (GG) or the risk allele (TT) had mild reductions (6% and 14%) in progression to advanced AMD when taking antioxidants and zinc compared with placebo
There was a trend toward significant interaction in heterozygous individuals with antioxidants plus zinc treatment reducing the probability of progressing to advanced AMD by approximately 46% (P=0.06).

Author Conclusion:

This study's major finding was evidence of a possible interaction between CFH genotype and treatment with antioxidants plus zinc when compared with placebo. This interaction seems to have arisen because supplementation was associated with a greater risk reduction in AMD progression (68%) in those with the low-risk TT genotype compared with those in the high risk CC genotype (11%). These results may imply that the strong genetic predisposition to AMD conferred by the CC genotype limits the benefits available from zinc and antioxidants.

The results suggest that treatment response to commonly used oral AREDS-type supplements may be affected by an individual's genotype. Specifically, the major benefit was seen in those individuals with low-risk CFH genotype who could lower their rate of AMD progression by approximately two thirds. By contrast, AREDS-type supplements seem to have less impact on those with high risk CFH genotype, although they still had an effect.

The authors do no believe that the study results justify routine genetic testing at this time. Although treatment effect may vary by CFH genotype, some benefit is derived by individuals in all CFH genotype groups and no effective alternative interventions are currently available. Corroboration of these findings would be needed before consideration is given to altering current management.

Funding Source:

Government:

National Eye Institute, National Institutes of Health, China National Science Foundation

University/Hospital:

Macular Degeneration Research Fund, Tufts-New England Medical Center

Not-for-profit

Foundation Fighting Blindness, Macular Vision Research Foundation, Macular Degneration Center Research Fund, Goodall Macular Degeneration Fund, Casey Eye Institute, Lions Eye Research Fund

Reviewer Comments:

The authors note the following limitations due to sample size:

Effect of Zinc

The possibility was explored that interaction between the CFH genotype and treatment was observed because of the effect of zinc
A significant interaction was found in the two groups taking zinc vs. the two groups taking no zinc, whereas, no interaction was observed when comparing those taking antioxidants with those taking no antioxidants
This suggests that the genotype-treatment interaction in participants with the CFH TT genotype may be related primarily to the zinc component of the supplements
One would expect to find a significant interaction between zinc vs. placebo comparison
The non-significant zinc vs. placebo comparison is probably at least partly related to the smaller sample size (n=421) in contrast to the zinc vs. no zinc comparison (n=876).

Genotype and Treatment Assignment

It was considered whether genotype and treatment assignment may be involved in reducing progression to specific types of AMD (neovascular AMD, geographic atrophy or both)
For reasons of sample size, no clinically meaningful data were obtained.

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)	Yes
	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)	Yes

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?	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?		Yes
	5.1.	In intervention study, were subjects, clinicians/practitioners, and investigators blinded to treatment group, as appropriate?	???
	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?	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?	Yes
	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?	Yes
	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?	Yes
	6.6.	Were extra or unplanned treatments described?	No
	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?	Yes
	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