Abstract
Purpose:
To assess whether genotypes at 2 major loci associated with age-related macular degeneration (AMD), complement factor H (CFH), or age-related maculopathy susceptibility 2 (ARMS2), modify the response to oral nutrients for the treatment of AMD in the Age-Related Eye Disease Study 2 (AREDS2).
Design:
Post hoc analysis of a randomized trial.
Participants:
White AREDS2 participants.
Methods:
AREDS2 participants (n = 4203) with bilateral large drusen or late AMD in 1 eye were assigned randomly to lutein and zeaxanthin, omega-3 fatty acids, both, or placebo, and most also received the AREDS supplements. A secondary randomization assessed modified AREDS supplements in 4 treatment arms: lower zinc dosage, omission of β-carotene, both, or no modification. To evaluate the progression to late AMD, fundus photographs were obtained at baseline and annual study visits, and history of treatment for late AMD was obtained at study visits and 6-month interim telephone calls. Participants were genotyped for the singlenucleotide polymorphisms rs1061170 in CFH and rs10490924 in ARMS2. Bivariate frailty models using both eyes were conducted, including a gene–supplement interaction term and adjusting for age, gender, level of education, and smoking status. The main treatment effects, as well as the direct comparison between lutein plus zeaxanthin and β-carotene, were assessed for genotype interaction.
Main Outcome Measures:
The interaction between genotype and the response to AREDS2 supplements regarding progression to late AMD, any geographic atrophy (GA), and neovascular AMD.
Results:
Complete data were available for 2775 eyes without baseline late AMD (1684 participants). The participants (mean age ± standard deviation, 72.1±7.7 years; 58.5% female) were followed up for a median of 5 years. The ARMS2 risk allele was associated significantly with progression to late AMD and neovascular AMD (P = 2.40 × 10−5 and P = 0.002, respectively), but not any GA (P 0.097). The CFH risk allele was not associated with AMD progression. Genotype did not modify significantly the response to any of the AREDS2 supplements.
Conclusions:
CFH and ARMS2 risk alleles do not modify the response to the AREDS2 nutrient supplements with respect to the progression to late AMD (GA and neovascular AMD). Ophthalmology 2019;■:1–8 Published by Elsevier on behalf of the American Academy of Ophthalmology
Age-related macular degeneration (AMD), a progressive retinal disease that can lead to severe visual impairment, is characterized by drusen and pigmentary changes in the retina in the early stage, expansion of drusen size and area in the intermediate stage, and the development of geographic atrophy (GA), choroidal neovascularization, or both in the late stage. As the leading cause of blindness in the developed world, AMD poses an enormous health care burden on society. Despite our increasing understanding of the pathogenesis of AMD, no cure exists to date. However, we can slow the progression of AMD through dietary modifications. The clinical trial results of the Age-Related Eye Disease Study 1 (AREDS1) revealed that intake of high-dose supplements of antioxidants in combination with zinc reduces progression to late AMD by 25% over 5 years in people with intermediate AMD in both eyes or late AMD in 1 eye.1
Genotyping in AMD to predict potential response to AMD treatments has been controversial. Although AMD pathogenesis has a clear genetic component, we have no conclusive evidence that routinely applying genetic testing can change the management of AMD.2 Several groups have tried to identify genetic subgroups within the AREDS1 population that respond differently to the dietary supplements. Varying results have been published, some indicating there are genetic subgroups with differential treatment response,3–7 whereas others do not find significant genetic interaction.8–10 A recent independent study from 3 different academic centers evaluated all previously reported data and independently assessed for data concordance for replication of these results.10 All 3 groups concluded that there was no basis for genotype-driven treatment. All analyses were performed using the AREDS1 clinical trial data, and because no other studies of the same magnitude are available, replication in an independent study cohort has not been possible. Based on the inconsistent evidence for modification of treatment response by genotype and the lack of external validation, the AREDS investigators and others recommend AREDS supplement treatment to all individuals with bilateral intermediate AMD or late AMD in 1 eye and do not recommend genetic testing before the start of treatment.2,8–10
The Age-Related Eye Disease Study 2 (AREDS2) was a randomized controlled trial that assessed several modifications of the original AREDS formula on AMD progression by adding lutein and zeaxanthin, adding omega-3 fatty acids, lowering the zinc dosage (from 80 mg to 25 mg), eliminating β-carotene, or a combination thereof. We found no beneficial nor harmful primary effect of omega-3 fatty acids on disease progression, nor was there a difference between the 2 zinc dose groups.11 In a secondary analysis, lutein and zeaxanthin reduced the risk of neovascular AMD compared with β-carotene, and in the primary analyses, lutein and zeaxanthin reduced the adverse effect of lung cancer.11 This then led to a change in the AREDS formula by replacing β-carotene with lutein and zeaxanthin.12 Despite the lack of any effect in most treatment arms, we were interested in analyses of genetic interaction with these oral supplements. When there is an interaction between genotype and treatment, it means that the response to the treatment differs depending on an individual’s genotype. Interaction between diet and genotype has been described before and could point toward relevant subgroups. Among others, dietary lutein and zeaxanthin, omega-3 fatty acids, and zinc have been shown to interact with the complement factor H (CFH) risk polymorphism, whereas the age-related maculopathy susceptibility 2 (ARMS2) risk allele has been shown to modify the effect of dietary omega-3 fatty acids and zinc on early AMD development.13 We took this opportunity to evaluate for any interaction between the 2 major CFH and ARMS2 risk alleles and the response to dietary supplements tested in AREDS2 for treatment of AMD.
Methods
Study Population
The AREDS2 design has been described previously and its primary outcomes have been reported.11,14 In summary, AREDS2 was a randomized clinical trial (carried out from 2006 through 2012) of 4203 participants who either had bilateral large drusen or had late AMD in one eye and large drusen in the fellow eye at baseline. They were followed up for up to 6 years (median, 5 years). It was designed in succession to the AREDS1 to evaluate additions to and modifications of the original AREDS formula, consisting of vitamin C (500 mg) and vitamin E (400 IU), β-carotene (15 mg), and zinc oxide (80 mg), along with cupric oxide (2 mg). In the primary randomization of AREDS2, the following supplement additions were assessed: (1) lutein 10 mg plus zeaxanthin 2 mg, (2) omega-3 long-chain polyunsaturated fatty acids (docosahexaenoic acid 350 mg plus eicosapentaenoic acid 650 mg), (3) both, or (4) placebo. In the secondary randomization evaluating a further modification of the original AREDS formula, individuals were randomized to the following 4 arms: (1) lower zinc dose (25 mg),(2) elimination of β-carotene, (3) both, or (4) no modification of the original AREDS formula. Participants not in the secondary randomization group were offered AREDS supplements as well, so in total, 99.5% of participants received the AREDS supplements or a modification thereof.
For the purpose of this genetic study, only white AREDS2 participants with complete data, including genotype information, were included (n = 1684) and only eyes without late AMD at baseline were analyzed (n = 2775). Each clinical center participating in AREDS2 obtained institutional review board approval for the study protocol, and all participants signed the study’s informed consent form. The study adhered to the tenets of the Declaration of Helsinki and complied with the Health Insurance Portability and Accountability Act.
Outcomes
The primary outcome of this study was to test for interaction between genotype and dietary supplements for AMD treatment in AREDS2. Specifically, we evaluated whether the effects on progression to late AMD of lutein and zeaxanthin supplementation, omega-3 fatty acid supplementation, β-carotene supplementation, and low versus high zinc dose differed according to CFH and ARMS2 genotype. In addition to its main effect, we also tested whether there was an influence of genotype for the direct comparison of lutein and zeaxanthin with β-carotene. To determine progression of AMD, participants received baseline and subsequent annual eye examinations and stereoscopic fundus photographs and 6-month interim telephone calls to obtain history of treatment for AMD. All fundus photographs were graded in a masked fashion by a central reading center using a standardized protocol. Late AMD was defined as the occurrence of either neovascular AMD or any GA. Neovascular AMD was defined by the presence of blood, fluid, hard exudate, retinal pigment epithelial detachment, or scarring on color fundus photography or based on history of treatment with intravitreal antie–vascular endothelial growth factor injections or other therapies for neovascular AMD such as photodynamic therapy. Any GA included central and noncentral GA and was defined as a lesion of at least 430 mm in diameter with loss of retinal pigment epithelium, circular shape, and well-demarcated margins on color photographs.
Genotyping
The AREDS2 participants had undergone genotyping using a custom Illumina HumanCoreExome array (Illumina, San Diego, CA) as part of the International AMD Genomics Consortium, as described previously.15 The risk alleles rs1061170 in the CFH gene and rs10490924 in ARMS2 gene are the main genetic contributors to AMD and therefore are important candidates to test for supplement interaction. Risk alleles were coded as presence of 0, 1, or 2 alleles, and additivity of risk alleles was assumed. In addition, we performed secondary analyses using the genotype groups (GTGs) as created in a previous publication by Awh et al4 for genetic interaction with the original AREDS formula. The 4 GTGs were construed using the CFH rs3766405 and rs412852 and the ARMS2 rs10490924 genotypes.
Statistical Analysis
Baseline differences between the randomization groups were assessed by standardized mean difference and P values based on 2-sample t tests for continuous factors, z tests for factors with 2 categories, and chi-square tests for factors with more than 2 categories. Progression to all types of late AMD was assessed on an eye level by a bivariate frailty model, which is an extension of the conventional Cox proportional hazards model. The frailty term adds a random effect to the model and allows for using the eye as unit of analysis accounting for the correlation between eyes of the same individual.16,17 All models were performed for the 3 different outcomes: progression to late AMD, neovascular AMD, or GA. To test for genotype–treatment interaction, the model included the treatment factor, genotype, and the interaction term between both. Models were adjusted for demographic factors that were related significantly to AMD progression (P < 0.05): age, gender, smoking status (never, past, current), and education level (high school or less, at least some college, postgraduate study). To assess the effect of genotype on AMD progression, both the CFH and ARMS2 single nucleotide polymorphisms were included in the model. Effect sizes are reported as hazard ratios (HRs) with 95% confidence intervals (CIs). Age-related macular degeneration progression according to subgroups was visualized by Kaplan-Meier curves. All analyses were performed in R software version 3.4.2 (R Foundation for Statistical Computing, Vienna, Austria), using the survival package17 coxph() function version 2.38 (R Foundation for Statistical Computing) for bivariate frailty models. Statistical significance for interaction was determined at a Bonferroni-corrected P value of0.0017 (0.05 per 30 tests) to account for multiple testing.
Results
Of the 4203 enrolled AREDS2 participants, 1684 were white and had complete data, including genotype information. The baseline characteristics of this population are described in Table 1. The subpopulation used in this study closely resembles the total AREDS2 population as shown in Table S1 (available at www.aaojournal.org). The 4 main randomization groups were highly similar, although there were slightly more women in the group that received both omega-3 fatty acids and lutein and zeaxanthin compared with the control group (Table S2, available at www.aaojournal.org). The analyses included 2775 eyes without late AMD at baseline. Over the course of 6 years, 964 eyes demonstrated late AMD, 515 demonstrated neovascular AMD, and 530 demonstrated any GA.
Table 1.
Population Characteristics of White Age-Related Eye Disease Study Participants with Complete Data
| Primary Randomization Group | ||||
|---|---|---|---|---|
| Omega-3 Fatty Acids | Lutein and Zeaxanthin | Both | Control (Standard of Care: Using Age-Related Eye Disease Study Supplements)* | |
| Participants (no.) | 449 | 418 | 414 | 403 |
| Eyes without late AMD at baseline (no.) | 744 | 690 | 668 | 673 |
| Demographics | ||||
| Mean age (SD) | 72.5 (7.7) | 72.0 (8.0) | 72.1 (7.7) | 71.7 (7.6) |
| Female gender, no. (%) | 262 (58.4) | 240 (57.4) | 261 (63.0) | 222 (55.1) |
| Smoking status, no. (%) | ||||
| Never | 197 (43.9) | 195 (46.7) | 176 (42.5) | 162 (40.2) |
| Past | 231 (51.4) | 196 (46.9) | 217 (52.4) | 211 (52.4) |
| Current | 21 (4.7) | 27 (6.5) | 21 (5.1) | 30 (7.4) |
| Education, no. (%) | ||||
| High school or less | 140 (31.2) | 116 (27.8) | 125 (30.2) | 109 (27.0) |
| At least some college | 215 (47.9) | 215 (51.4) | 199 (48.1) | 198 (49.1) |
| Postgraduate study | 94 (20.9) | 87 (20.8) | 90 (21.7) | 96 (23.8) |
| Genotype, no. (%) | ||||
| ARMS2 rs10490924 | ||||
| Low risk (GG) | 175 (39.0) | 163 (39.0) | 160 (38.6) | 151 (37.5) |
| Medium risk (GT) | 182 (40.5) | 181 (43.3) | 184 (44.4) | 179 (44.4) |
| High risk (TT) | 92 (20.5) | 74 (17.7) | 70 (16.9) | 73 (18.1) |
| CFH rs1061170 | ||||
| Low risk (TT) | 73 (16.3) | 74 (17.7) | 72 (17.4) | 62 (15.4) |
| Medium risk (TC) | 193 (43.0) | 182 (43.5) | 181 (43.7) | 166 (41.2) |
| High risk (CC) | 183 (40.8) | 162 (38.8) | 161 (38.9) | 175 (43.4) |
| Secondary randomization, no. (%)† | ||||
| β-carotene | ||||
| Yes | 145 (49.5) | 135 (53.1) | 117 (44.5) | 134 (49.8) |
| No | 148 (50.5) | 119 (46.9) | 146 (55.5) | 135 (50.2) |
| Zinc dose | ||||
| High | 159 (49.4) | 141 (49.3) | 154 (52.7) | 151 (50.3) |
| Low | 163 (50.6) | 145 (50.7) | 138 (47.3) | 149 (49.7) |
AMD = age-related macular degeneration; SD = standard deviation.
Treatment arm in which the participant received placebo for the lutein and zeaxanthin and the omega 3 randomization. However, almost all participants also received the Age-Related Eye Disease Study supplements.
Numbers are on the participant level. One thousand seventy-nine participants with complete data underwent randomization for β-carotene and 1200 participants underwent randomization for low (25 mg) versus high (80 mg) zinc.
Carriers of the rs10490924 risk allele in the ARMS2 gene were at significantly greater risk of late AMD developing (HR, 1.35; 95% CI, 1.17–1.55; P = 2.40 × 10−5) and neovascular AMD developing (HR, 1.29; 95% CI, 1.09–1.52; P= 0.002), but not any GA (HR,1.16; 95% CI, 0.97–1.38; P = 0.097). Carrying the CFH rs1061170 risk allele did not increase the risk of late AMD developing (HR,0.96; 95% CI, 0.84–1.11; P = 0.581), neovascular AMD developing (HR, 0.90; 95% CI, 0.77–1.07; P = 0.225), or any GA developing (HR, 1.09; 95% CI, 0.92–1.31; P = 0.325). The accompanying Kaplan-Meier curves are plotted in Figure S1 (available at www.aaojournal.org).
There was no significant interaction between lutein and zeaxanthin, omega-3 fatty acids, β-carotene, or zinc dose and CFH rs1061170 or ARMS2 rs10490924 genotype with regard to the progression to late AMD, neovascular AMD, or any GA (Table 2). Also, for the direct comparison of lutein and zeaxanthin with β-carotene, we did not detect any effect modification by genotype. Although none of the interaction terms reached statistical significance, we inspected the effects across the different genotype subgroups (Table 3). There was a marginally significant protective effect of low zinc compared with high zinc on development of any GA in individuals homozygous for the ARMS2 risk allele (HR, 0.62; 95% CI, 0.38–0.99; P = 0.047). The overall interaction term showed a nonsignificant trend (P = 0.050), but none of the associations remained significant after Bonferroni correction for multiple testing, and therefore, this finding cannot be considered statistically significant. For β-carotene, there are some suggestive effects for progression to late AMD, implying that β-carotene may be increasing risk, especially in persons with 0 or 1 CFH risk alleles or 1 or 2 ARMS2 risk alleles. Similarly, in the direct comparison of lutein and zeaxanthin with β-carotene, lutein and zeaxanthin seem to be protective for late AMD progression compared with β-carotene in the same genotype groups. The overall interaction term was not significant for β-carotene or for the comparison of lutein and zeaxanthin with β-carotene, and the direction of effect as shown in Table 3 was in favor of lutein and zeaxanthin within all genotype groups. Taken together, this implies that lutein and zeaxanthin are preferable to β-carotene regardless of genotype. Kaplan-Meier curves for each of the genotype–treatment interactions are plotted in Figure S2 (available at www.aaojournal.org) for the progression to late AMD, Figure S3 (available at www.aaojournal.org) for development of neovascular AMD, and Figure S4 (available at www.aaojournal.org) for development of any GA.
Table 2.
Interaction Results for Genotype and Treatment Arm
| Late Age-Related Macular Degeneration | Neovascular Age-Related Macular Degeneration | Any Geographic Atrophy | |||||||
|---|---|---|---|---|---|---|---|---|---|
| β-Coefficient | Standard Error | P Value for Interaction | β-Coefficient | Standard Error | P Value for Interaction | β-Coefficient | Standard Error | P Value for Interaction | |
| CFH | |||||||||
| Lutein and zeaxanthin | 0.195 | 0.125 | 0.118 | 0.210 | 0.146 | 0.151 | 0.111 | 0.156 | 0.479 |
| Omega-3 fatty acids | 0.137 | 0.125 | 0.272 | 0.188 | 0.146 | 0.197 | 0.099 | 0.156 | 0.526 |
| Low vs. high zinc | −0.187 | 0.143 | 0.192 | −0.083 | 0.169 | 0.624 | −0.287 | 0.181 | 0.113 |
| β-carotene | −0.165 | 0.151 | 0.276 | −0.199 | 0.180 | 0.270 | −0.018 | 0.192 | 0.924 |
| Lutein vs. β-carotene | 0.155 | 0.204 | 0.447 | 0.237 | 0.241 | 0.325 | 0.006 | 0.260 | 0.982 |
| ARMS2 | |||||||||
| Lutein and zeaxanthin | −0.121 | 0.122 | 0.321 | 0.065 | 0.143 | 0.649 | −0.170 | 0.153 | 0.267 |
| Omega-3 fatty acids | 0.025 | 0.122 | 0.835 | −0.057 | 0.143 | 0.693 | 0.121 | 0.153 | 0.428 |
| Low vs. high zinc | −0.144 | 0.141 | 0.308 | 0.080 | 0.167 | 0.630 | −0.353 | 0.180 | 0.050 |
| β-carotene | 0.221 | 0.148 | 0.136 | 0.337 | 0.177 | 0.057 | −0.084 | 0.187 | 0.655 |
| Lutein vs. β-carotene | −0.298 | 0.195 | 0.127 | −0.092 | 0.228 | 0.686 | −0.155 | 0.246 | 0.529 |
A negative coefficient for interaction means that the effect of the treatment becomes more beneficial with higher genetic risk.
Table 3.
The Effect of Dietary Supplements in Strata According to the Number of CFH or ARMS2 Risk Alleles
| Late Age-Related Macular Degeneration | Neovascular Age-Related Macular Degeneration | Any Geographic Atrophy | ||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Supplements | CFH Risk Alleles | Hazard Ratio | 95% Confidence Interval | P Value | Hazard Ratio | 95% Confidence Interval | P Value | Hazard Ratio | 95% Confidence Interval | P Value |
| Lutein and zeaxanthin | 0 | 0.811 | 0.572–1.148 | 0.237 | 0.796 | 0.531–1.191 | 0.267 | 0.866 | 0.555–1.349 | 0.524 |
| 1 | 0.985 | 0.820–1.183 | 0.872 | 0.981 | 0.792–1.215 | 0.862 | 0.967 | 0.767–1.218 | 0.774 | |
| 2 | 1.197 | 0.927–1.546 | 0.168 | 1.210 | 0.893–1.640 | 0.219 | 1.080 | 0.790–1.475 | 0.630 | |
| Omega-3 fatty acids | 0 | 0.932 | 0.658–1.320 | 0.690 | 0.798 | 0.533–1.194 | 0.272 | 1.006 | 0.645–1.569 | 0.979 |
| 1 | 1.068 | 0.889–1.284 | 0.481 | 0.963 | 0.777–1.193 | 0.729 | 1.111 | 0.881–1.401 | 0.375 | |
| 2 | 1.225 | 0.948–1.582 | 0.120 | 1.162 | 0.857–1.577 | 0.333 | 1.227 | 0.897–1.676 | 0.200 | |
| Low vs. high zinc | 0 | 1.327 | 0.891–1.977 | 0.163 | 1.281 | 0.806–2.037 | 0.294 | 1.323 | 0.793–2.206 | 0.284 |
| 1 | 1.101 | 0.892–1.359 | 0.369 | 1.179 | 0.922–1.509 | 0.189 | 0.993 | 0.759–1.299 | 0.958 | |
| 2 | 0.914 | 0.680–1.228 | 0.549 | 1.085 | 0.760–1.550 | 0.652 | 0.745 | 0.516–1.076 | 0.117 | |
| β-carotene | 0 | 1.547 | 1.014–2.360 | 0.043 | 1.536 | 0.938–2.516 | 0.088 | 1.124 | 0.652–1.938 | 0.675 |
| 1 | 1.312 | 1.051–1.638 | 0.016 | 1.260 | 0.971–1.635 | 0.083 | 1.103 | 0.831–1.464 | 0.496 | |
| 2 | 1.113 | 0.817–1.516 | 0.498 | 1.033 | 0.709–1.505 | 0.867 | 1.083 | 0.740–1.586 | 0.681 | |
| Lutein vs. β-carotene | 0 | 0.632 | 0.362–1.103 | 0.106 | 0.632 | 0.329–1.213 | 0.168 | 0.862 | 0.420–1.768 | 0.685 |
| 1 | 0.738 | 0.549–0.991 | 0.044 | 0.802 | 0.568–1.132 | 0.209 | 0.867 | 0.594–1.264 | 0.457 | |
| 2 | 0.862 | 0.561–1.324 | 0.497 | 1.017 | 0.610–1.693 | 0.950 | 0.872 | 0.511–1.489 | 0.615 | |
| ARMS2 Risk Alleles | ||||||||||
| Lutein and zeaxanthin | 0 | 1.152 | 0.883–1.504 | 0.297 | 0.978 | 0.709–1.348 | 0.890 | 1.141 | 0.822–1.583 | 0.431 |
| 1 | 1.021 | 0.854–1.220 | 0.822 | 1.043 | 0.848–1.284 | 0.689 | 0.963 | 0.771–1.203 | 0.739 | |
| 2 | 0.904 | 0.652–1.254 | 0.546 | 1.114 | 0.765–1.621 | 0.574 | 0.813 | 0.537–1.229 | 0.326 | |
| Omega-3 fatty acids | 0 | 1.085 | 0.830–1.417 | 0.552 | 1.060 | 0.768–1.462 | 0.725 | 1.032 | 0.743–1.434 | 0.851 |
| 1 | 1.113 | 0.931–1.330 | 0.241 | 1.001 | 0.813–1.233 | 0.991 | 1.165 | 0.932–1.456 | 0.180 | |
| 2 | 1.141 | 0.823–1.582 | 0.428 | 0.946 | 0.650–1.377 | 0.772 | 1.314 | 0.870–1.986 | 0.194 | |
| Low vs. high zinc | 0 | 1.217 | 0.891–1.662 | 0.218 | 1.109 | 0.764–1.611 | 0.586 | 1.248 | 0.843–1.847 | 0.269 |
| 1 | 1.054 | 0.860–1.292 | 0.613 | 1.202 | 0.946–1.529 | 0.133 | 0.877 | 0.677–1.136 | 0.320 | |
| 2 | 0.913 | 0.630–1.323 | 0.630 | 1.303 | 0.843–2.015 | 0.234 | 0.616 | 0.382–0.994 | 0.047 | |
| β-carotene | 0 | 1.046 | 0.752–1.456 | 0.789 | 0.901 | 0.607–1.339 | 0.607 | 1.185 | 0.783–1.792 | 0.422 |
| 1 | 1.306 | 1.055–1.616 | 0.014 | 1.263 | 0.979–1.628 | 0.073 | 1.089 | 0.833–1.425 | 0.532 | |
| 2 | 1.629 | 1.104–2.404 | 0.014 | 1.769 | 1.114–2.807 | 0.016 | 1.002 | 0.612–1.640 | 0.994 | |
| Lutein vs. β-carotene | 0 | 0.992 | 0.638–1.543 | 0.971 | 0.914 | 0.536–1.558 | 0.74 | 0.987 | 0.572–1.704 | 0.962 |
| 1 | 0.737 | 0.552–0.983 | 0.038 | 0.833 | 0.595–1.166 | 0.287 | 0.845 | 0.586–1.219 | 0.368 | |
| 2 | 0.547 | 0.328–0.913 | 0.021 | 0.760 | 0.424–1.361 | 0.356 | 0.724 | 0.375–1.399 | 0.337 | |
Our secondary analysis using the 4 GTGs also did not show a genetic interaction after correction for multiple testing (Tables S3A, S3B, and S3C). A moderately suggestive interaction was found with the GTG and lutein versus β-carotene for progression to any GA (P = 0.116), but after inspection of the results per GTG stratum, none of the groups showed a significant difference between lutein and β-carotene.
Discussion
The number of individuals affected with AMD is increasing and constitutes a large worldwide health concern. The current therapeutic options are limited to neovascular AMD, and although antievascular endothelial growth factor has revolutionized the field, vision may decline despite treatment. There is no treatment for GA that potentially can lead to severe central vision loss. Therefore, broadly applicable preventive measures to preserve vision in the long term are of key importance in AMD management. The current recommendation based on the AREDS2 trial is antioxidants plus zinc and lutein and zeaxanthin instead of β-carotene for all individuals with bilateral intermediate AMD or late AMD in 1 eye. Although not indicated by previous studies so far, it is recognized that AMD is a multifactorial disorder and that individuals may require different treatment approaches depending on their genetic background. In this study, we assessed whether the dietary supplements evaluated in AREDS2 have a role in disease management in different genetic subgroups. We found that subgroups based on CFH or ARMS2 risk alleles did not respond differently to dietary supplements with either lutein and zeaxanthin, omega-3 fatty acids, β-carotene, or varying zinc doses. This was true for analyses by single-gene genotype or by groupings based on both CFH and ARMS2 genotypes.
The AREDS2 was not a replication of the initial AREDS clinical trial, but considering previous interaction studies performed in the AREDS, it is important to note that there was no significant effect of CFH or ARMS2 risk status on response to low or high zinc dosage. Studies in AREDS evaluated whether CFH and ARMS2 genotypes could modulate the effects of antioxidants alone, zinc alone, or the combination on AMD progression.3–6,8,10 Some studies found that zinc was more beneficial in persons without CFH risk alleles6 or even potentially harmful in individuals with high CFH risk, whereas zinc would be beneficial in ARMS2 risk allele carriers.3,4 However, in a subsequent larger study of the AREDS data, these findings could not be replicated and the AREDS investigators found no significant genotype interactions with any of the treatment arms.8 Further analyses by the AREDS investigators using a residual sample also failed to replicate any harmful effects of zinc with specific risk alleles.9 Although AREDS2 did not include a no-zinc arm, there was no sign of an interaction effect with zinc dose and any genetic subgroup. A nonsignificant interaction of ARMS2 and zinc dose was observed; however, this was in the opposite direction as reported previously. We cannot exclude that a plateau effect of zinc dose has precluded any interaction effect.
One other clinical trial evaluated the effect of omega-3 fatty acid supplementation on the development of neovascular AMD, limited to persons with neovascular AMD in the fellow eye.18 As in AREDS2, they found no main effect; however, they saw a protective effect exclusive to individuals without the CFH risk allele. We could not replicate this finding, even when we restricted our analyses to only persons with neovascular AMD in 1 eye (data not shown). This could be the result of a difference in population, but it also should be considered that their numbers were relatively small, especially after stratifying for genotype.
Previous epidemiologic studies have shown that certain dietary nutrients could negate the effect of a deleterious genotype on AMD development. In the Rotterdam Study, homozygous carriers for the CFH rs1061170 risk allele seemed to benefit the most from high dietary intake of zinc, lutein and zeaxanthin, and omega-3 fatty acids and were able to reduce their risk for early AMD substantially, almost to the level of a noncarrier.13 Similarly, fish consumed on a weekly basis, an important source of omega-3 fatty acids, was protective for late AMD in individuals carrying the homozygous CFH risk allele in the Blue Mountains Eye Study, although this finding was only marginally signifi-cant.19 Dietary omega-3 fatty acid intake also has been shown to be particularly beneficial in reducing AMD risk for individuals with the ARMS2 high-risk genotype in the Rotterdam Study and AREDS.13,20 In addition, dietary zinc reduced the effect of the ARMS2 risk allele on early AMD development.13 All in all, several gene–diet interactions have been found so far, and considering the complex nature of AMD, an interplay between genetics and environment is not inconceivable. A possible reason for the absence of a genotype interaction effect in AREDS2 could be that the previous epidemiologic studies assessed dietary intake in contrast to dietary supplements. First, supplements tend to be in much higher concentration than we usually ingest through our food. Second, micronutrients as part of a diet are much more complex and often are correlated with other dietary and health-related factors. Possibly, gene interactions with diet are not as relevant in dietary supplementation. Furthermore, results could be affected by population characteristics of the AREDS2. The epidemio-logic studies showing gene–diet interactions all were in a population-based setting and evaluated the progression from no AMD to early AMD. The AREDS2 participants already had intermediate AMD or worse and were are at very high risk of AMD progression, demonstrated by the finding that 964 of 2775 participant eyes (35%) showed progression to late AMD by the end of follow-up. It is possible that gene–diet interactions played a role only earlier on in disease development. It also was remarkable that the CFH risk allele, which is a major contributor to AMD risk, was not associated with AMD progression is this population. This could point to a homogeneously advanced population in which individuals already have reached a certain threshold of risk accumulation. The complement pathway has been shown to be related to drusen formation,21,22 and because the AREDS2 population all have large drusen, their complement profile no longer may be distinguishing. It also may be possible that genotypes other than CFH and ARMS2 interact with dietary factors on AMD progression. Herein, we focused on CFH and ARMS2 because these combined loci explain approximately half of AMD heritability and both have been implicated previously in gene–diet interactions in AMD.13,15,19,20 Future studies, preferably in bigger populations, could focus on other AMD-related genetic factors as well. Finally, it should be noted that this study, like all previous supplement–gene interaction studies, was a post hoc analysis and that AREDS2 therefore was not powered to identify genetic interactions. Despite this limitation, very large effects likely would have been detected. Larger studies would be needed to exclude any small interaction effects from these genotypes, although clinical relevance with very small effects is questionable.
In conclusion, we were not able to identify any genetic subgroup that specifically did or did not benefit from any of the supplements investigated in AREDS2 with regard to the progression to late AMD. Based on our results, we do not propose any changes to the current AREDS2 recommendations for any genetic subgroup. Patients with intermediate AMD or late AMD in 1 eye should be recommended to consider taking AREDS2 supplements.
Supplementary Material
Acknowledgments
Supported by the Intramural Research Program of the National Eye Institute, National Institutes of Health, Bethesda, Maryland (grant nos.: EY000546, AREDS2 contract HHS-N-260-2005-00007-C, ADB contract NO1-EY-5–0007, and AREDS contract NOI-EY-0–2127); and the following National Institutes of Health institutes (funds contributed to AREDS2 contracts): Office of Dietary Supplements, National Center for Complementary and Alternative Medicine; National Institute on Aging; National Heart, Lung, and Blood Institute; and National Institute of Neurological Disorders and Stroke. The AREDS1 and AREDS2 sponsor and funding organization participated in the design and conduct of the study; data collection, management, analysis, and interpretation; and the preparation, review, and approval of the manuscript. Also supported by the Intramural Research Program of the National Eye Institute (grant no.: EY000546 [T.E.C., M.L.K., E.Y.C.]); the Nederlandse Oogonderzoek Stichting (F.v.A.); Dr. P. Binkhorst Stichting (F.v.A.); Stichting Dondersfonds (F.v.A.); Prins Bernhard Cultuurfonds (F.v.A.); and Stichting A.F. Deutman Oogheelkunde Researchfonds (F.v.A.). These organizations had no role in the design or conduct of this research. The National Institutes of Health holds a royalty-bearing license issued to Bausch and Lomb for the Age-Related Eye Disease Study Supplement.
HUMAN SUBJECTS: Human subjects were included in this study. The IRB/ethics committee of each participating clinical center approved this study. The AREDS study was approved by the National Eye Institute IRB for Human Subjects for this multicenter study. All research adhered to the tenets of the Declaration of Helsinki. All participants provided informed consent.
No animal subjects were included in this study.
Abbreviations and Acronyms:
- AMD
age-related macular degeneration
- AREDS
Age-Related Eye Disease Study
- AREDS1
Age-Related Eye Disease Study 1
- AREDS2
Age-Related Eye Disease Study 2
- ARMS2
age-related maculopathy susceptibility 2
- CFH
complement factor H
- CI
confidence interval
- GA
geographic atrophy
- GTG
genotype group
- HR
hazard ratio
Footnotes
Members of the Age-Related Eye Disease Study 2 Research Group are available online at www.aaojournal.org.
Financial Disclosure(s):The author(s) have no proprietary or commercial interest in any materials discussed in this article.
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