Dietary flavonoids are associated with longitudinal treatment outcomes in neovascular age-related macular degeneration

The effect of caffeine consumption on age-related macular degeneration: a systematic review and meta-analysis

PURPOSE

To explore the state-of-the-art evidence on the effect of caffeine consumption on the development and progression of age-related macular degeneration (AMD), a significant cause of blindness worldwide.

METHODS

Eligible primary clinical studies published up to 15 June 2024 were included and appraised using the Joanna Briggs Institute critical appraisal tools for cohort and case-control studies. The available data were then analyzed using random-effects meta-analysis and effect direction-based vote-counting (PROSPERO CRD42023451237).

RESULTS

Five studies (9318 patients) were included in this systematic review, three of which investigated the effect of caffeine intake on the development of AMD and two on AMD progression. Caffeine intake from coffee or other beverages showed no significant association with the occurrence of early (adjusted odds ratio 1.11 [95% confidence interval 0.93-1.33], I2 = 0.0%) or late AMD. On the other hand, vote-counting analysis indicated that caffeine consumption, mainly tea, may prevent and hinder disease progression, potentially in a dose-dependent manner.

CONCLUSION

The limited available evidence suggests that caffeine consumption may deter and impede the progression of AMD. In contrast, the protective effect of caffeine consumption on the development of AMD remains uncertain. Further prospective, large-scale studies exploring the effects and dose-response relationship of various caffeine beverages across a broader spectrum of AMD and populations are warranted to corroborate our findings.

Cocoa Flavanol Supplementation and Risk of Age-Related Macular Degeneration: An Ancillary Study of the COSMOS Randomized Clinical Trial

Importance

Abnormalities of choroidal blood flow in the eye are associated with occurrence of age-related macular degeneration (AMD). Cocoa flavanols show beneficial effects on vascular risk factors in small and short-term trials and may help reduce AMD risk.

Objective

To examine whether daily supplementation with cocoa extract, a source of flavanols, prevents the development or progression of AMD.

Design, Setting, and Participants

This was a prespecified ancillary study of the COSMOS (COcoa Supplement and Multivitamins Outcomes Study) trial, a double-blind, placebo-controlled, 2 × 2 factorial randomized clinical trial of a cocoa extract supplement and a multivitamin supplement in the prevention of cardiovascular disease and cancer among 21 442 US adults, including 12 666 women aged 65 years and older and 8776 men aged 60 years and older. The intervention phase was performed from June 2015 through December 2020; data analysis was completed in August 2024.

Intervention

Cocoa extract supplement (500 mg/day cocoa flavanols, including 80 mg (-)-epicatechin) or placebo.

Main Outcomes and Measures

The primary end point was a composite of incident cases of AMD plus cases of progression to advanced AMD (geographic atrophy, neovascular membrane, retinal pigment epithelium detachment, or disciform scar) among participants with AMD at baseline, based on self-report confirmed by medical record review.

Results

Mean (SD) participant age was 72.1 (6.6) years, and 12 666 participants (59.1%) were female. During a median (IQR) period of 3.6 (3.2-4.2) years of treatment and follow-up, 344 participants (1.6%) experienced a confirmed AMD event (316 incident AMD, 28 progression to advanced AMD). For the primary composite end point, there were 159 cases (1.5%) in the cocoa extract group and 185 cases (1.7%) in the placebo group (hazard ratio [HR], 0.87; 95% CI, 0.71-1.08; P = .21). Separate Cox models fitted because of evidence of nonproportional hazards (P = .048) indicated a 23% decreased risk in the cocoa extract group during the first 2 years of treatment (HR, 0.77; 95% CI, 0.59-1.01), with no added benefit for treatment beyond 2 years (HR, 1.06; 95% CI, 0.76-1.50). Similar time-dependent findings were observed for the secondary trial outcomes of incident visually significant AMD and advanced AMD.

Conclusions and Relevance

In this ancillary study of the COSMOS randomized clinical trial, cocoa extract supplementation for a median period of 3.6 years among older women and men had no effect overall on occurrence of AMD. However, a possible modest treatment effect early in the trial could not be ruled out, which warrants further investigation to clarify whether cocoa extract may help reduce AMD risk.

Trial Registration

ClinicalTrials.gov Identifier: NCT03205202.

Natural products for the treatment of age-related macular degeneration

BACKGROUND

Age-related macular degeneration (AMD) is a chronic retinal disease that significantly influences the vision of the elderly.

PURPOSE

There is no effective treatment and prevention method. The pathogenic process behind AMD is complex, including oxidative stress, inflammation, and neovascularization. It has been demonstrated that several natural products can be used to manage AMD, but systematic summaries are lacking.

STUDY DESIGN AND METHODS

PubMed, Web of Science, and ClinicalTrials.gov were searched using the keywords "Biological Products" AND "Macular Degeneration" for studies published within the last decade until May 2023 to summarize the latest findings on the prevention and treatment of age-related macular degeneration through the herbal medicines and functional foods.

RESULTS

The eligible studies were screened, and the relevant information about the therapeutic action and mechanism of natural products used to treat AMD was extracted. Our findings demonstrate that natural substances, including retinol, phenols, and other natural products, prevent the development of new blood vessels and protect the retina from oxidative stress in cells and animal models. However, they have barely been examined in clinical studies.

CONCLUSION

Natural products could be highly prospective candidate drugs used to treat AMD, and further preclinical and clinical research is required to validate it to control the disease.

Role of traditional Chinese medicine in age-related macular degeneration: exploring the gut microbiota's influence

The pathogenesis of age-related macular degeneration (AMD), a degenerative retinopathy, remains unclear. Administration of anti-vascular endothelial growth factor agents, antioxidants, fundus lasers, photodynamic therapy, and transpupillary warming has proven effective in alleviating symptoms; however, these interventions cannot prevent or reverse AMD. Increasing evidence suggests that AMD risk is linked to changes in the composition, abundance, and diversity of the gut microbiota (GM). Activation of multiple signaling pathways by GM metabolites, including lipopolysaccharides, oxysterols, short-chain fatty acids (SCFAs), and bile acids (BAs), influences retinal physiology. Traditional Chinese medicine (TCM), known for its multi-component and multi-target advantages, can help treat AMD by altering GM composition and regulating the levels of certain substances, such as lipopolysaccharides, reducing oxysterols, and increasing SCFA and BA contents. This review explores the correlation between GM and AMD and interventions for the two to provide new perspectives on treating AMD with TCM.

Dietary Flavonoid Intake and Chronic Sensory Conditions: A Scoping Review

Dietary flavonoids have antioxidant, anti-inflammatory, and vascular health benefits, which align with the proposed pathophysiology of age-related eye conditions and hearing problems (hearing loss and tinnitus). This scoping review is based on Arksey and O'Malley's six-stage framework and aims to summarise current evidence on the association between the dietary flavonoid intake and chronic sensory conditions in adults, and to identify the research gaps in this area. Eligible studies were identified by searching MEDLINE, EMBASE PsycINFO via the OVID platform, and Google Scholar, as well as manually searching the reference lists of the eligible articles. The inclusion criteria included: articles with full-text access, written in the English language, and focused on chronic sensory conditions and dietary flavonoid intake in an adult population. Studies focused on flavonoid supplements were excluded. Ten studies were included in this review. The evidence suggests that the flavonoid subclass, flavonols, are protective against eye conditions, including age-related macular degeneration, cataract, and glaucoma. There is insufficient evidence to support an association with hearing loss or tinnitus. Overall, dietary flavonol intake appears to be protective against some chronic eye conditions. However, for most eye and hearing-related conditions, only one study was identified. Thus, there is a need for more recent high-quality research to be conducted to confirm any significant associations.

Inherited Retinal Dystrophies: Role of Oxidative Stress and Inflammation in Their Physiopathology and Therapeutic Implications

Inherited retinal dystrophies (IRDs) are a large group of genetically and clinically heterogeneous diseases characterized by the progressive degeneration of the retina, ultimately leading to loss of visual function. Oxidative stress and inflammation play fundamental roles in the physiopathology of these diseases. Photoreceptor cell death induces an inflammatory state in the retina. The activation of several molecular pathways triggers different cellular responses to injury, including the activation of microglia to eliminate debris and recruit inflammatory cells from circulation. Therapeutical options for IRDs are currently limited, although a small number of patients have been successfully treated by gene therapy. Many other therapeutic strategies are being pursued to mitigate the deleterious effects of IRDs associated with oxidative metabolism and/or inflammation, including inhibiting reactive oxygen species’ accumulation and inflammatory responses, and blocking autophagy. Several compounds are being tested in clinical trials, generating great expectations for their implementation. The present review discusses the main death mechanisms that occur in IRDs and the latest therapies that are under investigation.