Findings from a recent study published in Ophthalmology evaluated whether chronic kidney disease (CKD) increases susceptibility to age-related macular degeneration (AMD) in Asian populations.
Give me some background first.
CKD and AMD share risk factors, pathogenic mechanisms, and genetic polymorphisms—indicating a potential association between the two conditions.
Investigators have noted unique AMD phenotypes and genetic signatures reported in Asians— consequently, the relationships between AMD and CKD may differ between Asians and other ethnic groups.
Is this the first study evaluating CKD and AMD?
Previous studies have resulted in inconclusive findings regarding renal function and AMD.
As a result, investigators of this research utilized comprehensive data from the Asian Eye Epidemiology Consortium—a collaborative network of population-based studies from 10 different Asian countries—to assess potential correlations.
Now, talk about the study.
In this cross-sectional study, researchers performed a pooled analysis using individual participant data to assess the associations between CKD and estimated glomerular filtration rate (eGFR)—a measure of kidney function—with early and late AMD.
In total, 51,253 participants (mean age 51.4±14.5 years, 54.7% female) from 10 population-based Asian studies were included in the study.
Participant data was adjusted for:
- Age
- Sex
- Hypertension
- Diabetes
- Body Mass Index (BMI)
- Smoking status
- Total cholesterol
- Study groups
How were AMD and CKD defined?
CKD was defined as eGFR below 60mL/min/1.73m2, and AMD was defined as either late or early AMD.
Definitions for early AMD integrated three distinct grading scales that broadly included the presence of soft drusen and retinal pigmentary epithelium (RPE) abnormalities, while late AMD included geographic atrophy (GA) or neovascular AMD.
Findings?
Within the cohort, the prevalence of CKD and AMD was as follows:
- CKD: 9.9%
- Early AMD: 9.0%
- Late AMD: 0.71%
After adjusting for confounding factors, patients with CKD were associated with almost 1.5 higher odds of late AMD (odds ratio [OR] 1.46, 95% confidence interval [CI] 1.11-1.93, P=0.008).
Tell me more.
Further, diminished kidney function (per 10-unit eGFR decrease) was associated with late AMD (OR 1.12, 95% CI 1.05-1.19, P=0.001).
Of note, CKD and eGFR were not significantly correlated with early AMD (all P>0.149).
Expert opinion?
According to the study authors, “CKD may lead to increased oxidative stress due to reduced glomerular filtration of free radical-generating nitrogenous waste products.”
Consequently, “the heightened oxidative stress can accelerate lipid deposition within Bruch’s membrane, which can further contribute to the degeneration and calcification of elastin and collagen.”
Meaning…
“This sequence ultimately results in the calcification of Bruch’s membrane, rendering it more vulnerable to breakdown under elevated intravascular pressure, leading to the formation of choroidal neovascularization,” they concluded.
Limitations?
While the size of the study bolstered the reliability of the findings, some limitations included:
- Slight variation in early AMD grading between the three grading systems used in the 10 studies
- Lack of additional renal function biomarkers, such as albuminuria or cystatin C serum concentration
- Inclusion of only Asian populations
Tie it all together for me.
These findings demonstrated that, within Asian populations, CKD and compromised kidney function are significantly associated with late AMD, highlighting the value of ocular examinations in CKD patients.
Further longitudinal and multiethnic studies elucidating whether kidney function can predict AMD progression in patients with early AMD are warranted.