In a meta-analysis published in BMC Ophthalmology, investigators reviewed previous studies to clarify the association between ambient air pollution and age-related macular degeneration (AMD).
Give me some background first.
While intravitreal injections of anti-vascular endothelial growth factor (anti-VEGF) are available to treat patients with AMD, unfortunately, not all individuals may benefit from it.
Let’s talk air pollution: As a major contributor to global disease burden, it is also associated with health hazards.
Some of the compounds that comprise ambient air pollution include:
- Nitrogen dioxide (NO2)
- Carbon monoxide (MO)
- Sulfur dioxide (SO)
- Ozone (O3)
- Particulate matter less than 2.5 μm in diameter
- PM2.5 and PM10 respectively
Now, talk about the study.
Researchers searched databases for relevant studies regarding pollution, its components, and AMD from January 1, 2000, to January 30, 2024. They also examined the original studies for references and reviews to identify other suitable data.
The databases that were searched included:
What were the inclusion and exclusion criteria?
Included studies had to:
- Refer to the association between ambient air pollution and AMD
- Contain calculable information
- I.e: Odds ratios (OR), hazard ratios (HRs), respective 95% confidence intervals (CI), and P values
- Be English-only peer-reviewed studies
- Use cross-sectional, prospective, or retrospective cohorts and case-control designs
Studies were excluded if they:
- Contained duplicate subjects
- Were abstracts, case reports, comments, reviews, or experimental study designs in a laboratory setting
- Did not contain necessary data
How was the study conducted?
Investigators extracted and reviewed the data collected for study quality. Out of the 358 studies they identified, eight were used for their analysis.
Then: They utilized a random-effects model to calculate pooled covariate-adjusted ORs and tested heterogeneity across all the studies.
Findings?
The researchers found that:
- Four studies evaluated the association between particulate matter less than 2.5 μm in diameter (PM2.5) and AMD
- Three studies explored the relationship between NO2 or O3 and AMD
- The pooled ORs for the respective three studies were:
- 1.16 (95% CI: 1.11-1.21)
- 1.17 (95% CI: 1.09–1.25)
- 1.06 (95% CI: 1.05–1.07)
- The pooled ORs for the respective three studies were:
The pooled ORs showed a positive correlation between ambient air pollution and AMD while also indicating high heterogeneity.
Limitations?
The study authors noted that the measurement variability of the exposure assessment and the quantitative differences of the exposure extent could bias the study results.
Go on …
The investigators used data of the highest quartile of two articles in their analysis and did not standardize the effect across all studies.
They mentioned that only a few studies passed the inclusion criteria; the small number of studies for every air contaminant made subgroup analysis by exposure level difficult.
Lastly, they stated other air pollutants could affect single-pollutant models.
Expert opinion?
The researchers recommended that further studies be conducted to analyze additional air pollution and its potential influence on AMD.
They also stated that further strategies to reduce ambient air pollution are vital for public health and could mitigate AMD.
Take home.
The findings of this research suggest that ambient air pollutants including PM2.5, NO2, and O3 may have a detrimental effect on AMD.