Study Identifies Alcohol Use as Potential Risk Factor for AMD Subtype

A new study provides genetic evidence that increased alcohol intake may be a causal risk factor for geographic atrophy (GA), a type of advanced age-related macular degeneration (AMD), but doctors caution that it may be too soon to advise patients about the risk.

“As there are currently no known treatments for GA, this finding has important public health implications,” wrote the authors of the study published in JAMA Ophthalmology.¹

The researchers also demonstrated an association between smoking and the risk of advanced AMD, which is a leading cause of blindness in Western countries and is growing in prevalence. In addition to GA, the other type of advanced AMD is neovascular AMD (nAMD), which can be treated with intravitreal injections of anti–vascular endothelial growth factor.

“These results also support previous observational studies associating smoking behavior with risk of advanced AMD, thus reinforcing existing public health messages regarding the risk of blindness associated with smoking,” they wrote.

The researchers examined genetic instruments composed of variants associated with risk factors at genome-wide significance for advanced AMD from the International AMD Genomics Consortium 2016 data set. The data included more than 16,000 individuals with AMD and 17,832 control patients, and they reviewed data from July 2020 through September 2021.

They reviewed smoking initiation, smoking cessation, lifetime smoking, age at smoking initiation, alcoholic drinks per week, body mass index, systolic and diastolic blood pressure, type 2 diabetes, glycated hemoglobin, fasting glucose, and fasting insulin.

The researchers found that a 1-SD increase in logodds of genetically predicted smoking initiation was associated with higher risk of advanced AMD (odds ratio [OR], 1.26), while a 1-SD increase in logodds of genetically predicted smoking cessation (former vs current smoking) was associated with lower risk of advanced AMD (OR, 0.66).

Genetically predicted increased lifetime smoking was associated with increased risk of advanced AMD (OR per 1-SD increase in lifetime smoking behavior, 1.32).

Genetically predicted alcohol consumption was associated with higher risk of GA (OR per 1-SD increase of log-transformed alcoholic drinks per week, 2.70).

There was insufficient evidence to suggest that genetically predicted blood pressure, body mass index, and glycemic traits were associated with advanced AMD.

However, the findings should not affect the advice that physicians give to patients about drinking alcohol and smoking, wrote Xinyi Su, MB, BChir, PhD, and Tien Yin Wong, MBBS, PhD, in an accompanying editorial.²

“Although this study has important implications whereby smoking and alcohol are important causal factors for both nAMD and GA, it is unlikely that changing either of these modifiable risk factors, in isolation, would be sufficient,” Su and Wong wrote.

Effective abstinence treatment hinges on a better understanding of how these substances—and their addictions—interact, they noted. “Perhaps, the best way forward is through a holistic approach, whereby the importance of an overall healthy lifestyle is recommended and supported by appropriate proper patient education.”

“It should be emphasized that these lifestyle-focused health care changes can only be achieved through effective comanagement between eye care practitioners and other health professionals, such as dieticians and general physicians,” Su and Wong stressed. “This will require the efforts of the entire health care community, not just the ophthalmologists alone.”

The study implies that smoking and alcohol have differential effects on nAMD and GA, and, as such, future studies could focus on examining the different pathologies underlying the 2 distinct forms of advanced AMD, they wrote.

“In addition, future studies can also look into the effect of smoking cessation and alcohol reduction programs on blindness prevention and interrogate the economic benefits of these strategies in reducing the global health care burden of AMD,” they added.

References

1. Kuan V, Warwick A, Hingorani A, et al; International AMD Genomics Consortium. Association of smoking, alcohol consumption, blood pressure, body mass index, and glycemic risk factors with age-related macular degeneration: a Mendelian randomization study. JAMA Ophthalmol. Published online November 4, 2021. doi:10.1001/jamaophthalmol.2021.4601

2. Su X, Wong TY. Revisiting the alcohol consumption association with age-related macular degeneration: what should we tell patients in 2021? JAMA Ophthalmol. Published online November 4, 2021. doi:10.1001/jamaophthalmol.2021.4602